My first visit to Florida is full of happy
memories; we had just been in Milwaukee, where the November snow
clouds had been threatening, so Florida came as a welcome relief,
with its tropical climate and vibrant life. We marvelled at brown
pelicans diving into still waters where king crabs lurched around
in the shallows, as present day relics of the Devonian era. One
day when we were driving through swampy country thick with water
hyacinth, the family was passing time counting dead animals on
the road. They were mainly skunks and rabbits then someone exclaimed:
"there's an armadillo!" I said: "it can't be -
they don't live here." But it was - so much for my zoological
knowledge: they didn't live there naturally, but they have been
introduced, together with the water hyacinth and Australian tea
trees. Manatees have been brought in to clear some of the water
hyacinth and beetles for the tea trees.
Armadillos have not learnt about cars - their
normal reaction to a predator is to use their armour-plating for
protection, like hedgehogs use their spines, so they stop or curl
up instead of running away like other animals, so as we drove
further more were spotted dead on the road. The skunks are even
more confident of their invincibility, and however hard drivers
may try and avoid skunking, the cars get skunked and the animals
get squashed. The skunks' stink had little effect on cars, but
it has an amazing effect of would-be predators, and, over the
eons of their evolutionary history, they have learned that they
have every right to walk around as if they own the world.
ARMADILLO ROAD-KILL. Like
skunks, armadillos have evolved very effective protection against
predators, and with this protection they have no need to be wary
of predators. They treat cars as if they were predators and suffer
the consequences. They are undergoing very rapid natural selection
to become aware that cars are different. Hedgehogs in Britain
appear to have acquired this necessary behaviour tool: they get
up and run from cars.
We saw the first monarch butterflies in Florida, huge orange butterflies
flying as if they had nothing to fear. They occupy a special place
in the minds of English butterfly collectors because they are
sometimes carried across the Atlantic, together with some other
insects which fly south for the winter. They are diverted by weather
systems, usually hurricanes, which carry them off course. In 1998
there were some Monarch sightings in England and large American
dragonflies appeared in the Scilly Isles. The dragonflies (known
as green darners) head for southern waters like Florida, while
the monarchs go on to Mexico where millions of them over-winter
in a single small valley. The monarchs treat predatory birds with
the same disdain as the skunks treat cars. They can lazily fly
around, blazing their bright colours, because they are deadly
poisonous and need to let birds know who they are.
The monarch is an amazing example of how natural
selection works. The story starts with the butterfly caterpillars
feeding on poisonous plants. Many caterpillars feed on poisonous
plants - the poisons are often made by the plant to try and deter
insect attack, but some insects manage to crack the code of detoxifying
the poison, and then become hooked on eating that plant alone.
The monarch feed on milkweeds containing poisonous cardiac glucosides,
which are particularly poisonous to vertebrates. Where they differ
from many other insects is that they can store the poison in such
a way that it is released if they are damaged. Birds trying to
eat the caterpillars are given a heavy taste of poison, which
is enough for them to learn to avoid them - however, novice birds
can die from eating them. This is such a magnificent weapon, that
in the course of evolution, the poison has become stored through
to the butterfly stage. The butterflies are also poisonous, and
leak poisonous fluid if caught; this is usually enough for a bird
to learn not to touch them a second time. Some birds, like the
blue jay will vomit after tasting a monarch butterfly.
MONARCH BUTTERFLY. Monarch caterpillars
feed on milkweeds and store poisons in their bodies which make
them poisonous to birds. The butterflies are also poisonous, so
are brightly coloured to warn birds that they are not good to
eat. Natural selection favours this behaviour as long as the caterpillars
feed on toxic plants - some do not, and run the risk of birds
learning this. Other insects also feed on these poisonous plants,
like the yellow aphis and red bugs. They are also poisonous.
The story does not end there - the monarch caterpillars
feed on a variety of milkweeds some with very little poison. This
is a dangerous habit because although the caterpillars grow well,
maybe better in the absence of poison, they run the risk of birds
finding out. If there are too many butterflies which are not poisonous,
then birds will learn that maybe it is worth a try: some butterflies
may make you vomit, but most are an easy meal. The birds are the
main avenue of natural selection, and so if too many are not poisonous,
all suffer, and selection pushes the butterflies back to seeking
the more poisonous plants for their eggs.
Other butterflies suffer from bird predation,
and so there is strong natural selection for wing patterns and
behaviour which encourage survival. When there are a lot of poisonous
monarchs flying around, it is then an advantage for other butterflies
to resemble a monarch, because birds will avoid them. Female viceroys
have done this very successfully - the males do not matter so
much and have kept their normal wing colours, probably because
they need to be recognisable to the females. The females however,
have taken on the cloak of the monarch, and can fly around in
relative safety and lay their eggs in peace. They also run the
risk of being found out if there are too many of them - so population
numbers are kept relatively low - helped by only part of the population
taking on the monarch wing pattern. When something works so well,
there is huge pressure to overcome it. The birds are all the time
being challenged by these poisonous butterflies, so their physiology
has become accustomed to ridding the body of the poison. This
is the same process, which led to the butterflies acquiring the
ability to avoid being poisoned when feeding on the plants. Most
birds cannot cope, but some have cracked it and can feed on the
butterflies with impunity.
VICEROY BUTTERFLY. Deception
is a common strategy in nature. This female viceroy butterfly
mimics the colour pattern of the poisonous monarch, but it is
not poisonous. The ruse works, as long as there are not too many
of them - if there are, birds learn that they are good to eat.
The rule is: if you are going to deceive, don't do it too often.
The males have a different wing pattern, so only half the population
of butterflies is involved in the deception.
This is one of' the many examples of use of poisons.
The zebra is another butterfly common in Florida - this belongs
to a large group of mainly Central and South American poisonous
species, which also have mimics riding on them too. Some, instead
of feeding on poisonous plants as caterpillars, acquire the poison
as adults - the males deliberately go and feed on poisonous exudates
and pass this poison on to the females when they mate!
These are the gross avenues of natural selection, which
lead Charles Darwin to write "The Origin of Species".
As we all know, he was particularly impressed by the birds on
the Galapagos islands where it was clear to him that birds had
made their way from the mainland to a range of islands, but in
the course of time they had changed so that each island had a
different form. He knew about unnatural selection where breeds
of dogs are made by human intervention - for the birds, he suggested
Natural Selection had taken place, where for each island, those
best suited had survived and reproduced at the expense of the
less fit ones. Since the islands differed and the acquired skills
of survival were also different, the birds ended up after many
generations looking quite unlike the original and were assigned
into different species. They became known as Darwin's Finches.
Had Darwin known of Gregor Mendel's painstaking
work on peas he might have found it much easier to write his book.
Mendel had stumbled upon the tool which made Natural Selection
work, but knew nothing of Darwin's ideas about natural selection.
He had found that inherited characters were programmed in genes,
and that these genes were mixed during pollination, and re-assorted
in the offspring. It has been suggested that Mendel, being a man
of the church, liked perfection, and some of his results were
a little too good to be true. He knew the result he expected,
and picked the best examples to fit his theory. It is comforting
to know that he was human, science is littered with results which
are too good to be true. Some have even planted information to
support what they "know" is the correct answer.
Like other areas of knowledge, it is the thought-processes
that produce ideas of how things work, but in science it is the
experimental work, which can support or quash these ideas, not
the written word. Even so, scientific dogma is sometimes very
difficult to overturn, and many brilliant ideas, with ample supporting
evidence, have been ridiculed and unpublished until the supporting
evidence becomes overwhelming - even then, some diehards refuse
to change their pet ideas. Mendel's experiments have led to a
whole new science of genetics which is much more complicated than
he thought, he was just lucky to have chosen some characters with
simple inheritance patterns. It was only later that the root mechanisms
were unearthed. Details of how natural selection works in nature
are still hotly disputed, but the mechanisms of inheritance are
well documented
There is a simplistic idea that genes are strung out along chromosomes
like beads, and that each bead represents some inherited character.
Each individual has two sets of chromosomes, one contributed by
the father and the other by the mother. This means that all genes
cannot be expressed - those which are, are said to be dominant
over those which are not which are called recessive. The human
genome project has documented something much more complex - the
sequence of base couplets on each chromosome - essentially the
chemical structure of the genome. This shows that each segment
known as a gene is very complex, and can code for a wide range
of enzymes. There is not a gene for everything, but each gene
is a complex of characters which go together. I don't know whether
any genetic studies have been done on the Monarch butterfly, but
there could be a gene for detoxifying cardiac glucosides (no doubt
a complex of characters) and this might go with the ability of
adult butterflies finding plants with high toxicity to lay their
eggs on. In the course of natural selection, these two characters
would do best if the were inherited together. To start with they
might be on different chromosomes, but over many generations,
if they are advantageous, they will eventually be brought together,
and come part of the same gene. Once they are together in a gene,
they are unlikely to be separated, so all offspring with this
gene have both these characters. Genes are thus mainly a group
of characters which need to be inherited together to function
properly. They may include other unrelated characteristics as
well.
The process of natural selection is based on the fact
that many eggs are produced and only a few survive to produce
the next generation. Each egg has a slightly different mix of
genes, and, although chance plays a large role, those which are
better adapted, tend to have a better chance of survival than
those that have a poor combination of genes. The bulk of genetic
material is shared by most forms of life - it is the basic structure
which was evolved billions of years ago, only tiny differences
are present between closely related species, such as human beings
and chimpanzees. Even smaller differences are present between
members of each species. Even so, mistakes are constantly being
made during reproduction when sections of DNA are incorrectly
transcribed. Most of these mutations are lethal, so the offspring
do not develop, some modify the organism in some way, and so add
a new dimension to the species, on which natural selection can
operate - one which turns the female viceroy orange instead of
blue, would normally be a disadvantage, because males would not
recognise it, but it would mean that they survive much longer,
and there would be strong natural selection on males to recognise
this new colour.
Natural selection and genetics are, of course, much more complicated
than this suggests, so much so that evolutionary biologists seem
to get so caught up in the detail that they appear to forget what
the actual principles are. What are the principles? Do they only
apply to living things or are they general? With sexually reproducing
living things the principles appear to be that of replication
- that parents produce offspring with a range of genetic variations,
and these each has different survival times and the better adapted
individuals are most likely to live long enough to reproduce themselves.
How can this be encapsulated into generalities? One needs (1)
a recognisable structure (2) some form of inheritance (3) survival
time in an arena bathed in energy, where the structure is tested
in an uncertain environment (by natural selection). Whatever the
structure, it can grow and change under these circumstances. Inheritance
is the only factor apparently dividing living from non-living,
but this may only be because living things are particularly good
at it - they pass on details encoded in DNA before they die. Most
other structures only encode in their constituent parts when they
die. A molecule of sodium chloride, for instance, leaves sodium
and chlorine ions when it breaks down, both of which are very
likely to reform into another molecule of sodium chloride. To
me this is a basic form of inheritance - parts which are likely
to come together to reform the whole. Brought down to these terms
perhaps everything in the Universe could be subject to evolution
by Natural Selection - it may be a universal law of nature.
Atoms are made of protons, neutrons and electrons;
they have long lives, but may spontaneously disintegrate or are
hit by a particle in the arena of space. The parts then become
available to reform another atom - the same kind or an even more
resilient kind - a form of inheritance? Chemists use the process
of natural selection to manufacture chemicals, they add ingredients
together and subject them to an artificial environment of, maybe,
heat and other chemicals so that the desired product becomes the
most likely of the compounds formed. Most chemical reactions involve
a reversible element, where more complex molecules will continually
break into constituent parts and reform. When this happens the
constituent parts essentially take on the role of inheritance
- they encourage the reformation of the more complex molecule,
they are like genes, just as protons, electrons and neutrons are
the genes of atoms, with the most stable atoms becoming the most
abundant according to the environment. With this view of Natural
Selection, there is no distinction between life, chemistry and
atomic physics, and it is a natural progression for life to appear
from simple chemistry in an active arena of space or on the surface
of a heavenly body.
Natural selection works in such a way that unbelievable
complexity can be built in a step-by-step process from simple
origins - the human eye is an oft-quoted example. The appearance
of complex structures seems to go against the laws of physics,
which point in the other direction - of destruction and decay.
But Natural Selection has the inevitable result of increasing
complexity because it is driven by the seemingly endless supply
of energy radiating to every corner of the Universe. Complexity
can build up, wherever there is a flux of energy, like a plant
growing in sunlight. Building such complexity often involves what
appear to be very unlikely happenings. The appearance of the precursors
of self-replicating molecules like RNA or DNA may well have been
very unlikely. But in a universe of astronomical numbers, unlikely
events such as the appearance of life, become almost certain.
In terms of structural integrity, self-replication is the first
step towards living things, and has a huge natural selection advantage
over simple chemical reactions, because they reproduce themselves.
It is interesting that chemists have already been able to create
some self-replicating molecules, unrelated to any form of life
we know here.
OLEANDER APHID FEEDING ON MILKWEED.
These aphids absorb the poison from the plants and are poisonous
themselves. Aphids can reproduce at a phenomenal rate with a process
of giving live births to young without mating. The populations
of aphids can be enormous and demonstrate how very rare events
- one in a billion - can become virtual certainties, if you are
dealing with populations of many billions of individuals.
One does not have to go far to find examples of how astronomical
numbers can lead to unlikely events becoming certainties. Every
bush one looks at has a host of insects associated with it. The
milkweeds are covered with other insects making use of the poison
- including aphids (which can also use deadly poisonous oleander)
and brilliant poisonous red bugs feeding on the seeds. Another
aphid attacks alfalfa, and is a serious pest in America. It first
arrived in 1953, probably from Europe. It became resistant to
organophosphate pesticides in 1956; in 1958 a resistant form of
alfalfa, was first attacked by the aphid; and in 1960 it began
over-wintering in the north - where it had been too cold for it
to survive before. This may seem the normal process of pest species
- of becoming resistant to our efforts at control. But this is
an especially interesting case, because the aphid that first came
and gave rise to the whole problem - was probably a single virgin
female (we could call her Lucy). This means that the first wave
was a clone of essentially identical aphids - because Lucy was
genetically programmed to reproduce only by asexual means - she
had directly developing eggs, giving birth to exact copies of
herself.
Errors sometimes occur during the cloning process,
as in all reproductive processes, but mutations in genes are regarded
as rare, only occurring at the rate of between one in 100,000
to one in a billion per generation. However, aphid populations
are commonly in the billions per generation, so mutations are
no longer unlikely - they are certainties! Having no form of sexual
reproduction actually makes it more likely that the changes will
occur, because any individual with an advantageous mutation, such
as for pesticide resistance, breeds true and founds a whole new
clone with this resistance. It is therefore unaffected by the
mixing and diluting process involved in sexual reproduction. The
alfalfa aphid, just by sheer numbers, managed to make the unlikely
happen - it even rediscovered sexual reproduction in the north,
because this gave it the ability to survive winters in a cold-resistant
egg stage, instead of relying on migration from the warm south
each spring.
MOONSHOT GETTING READY. This
is when people began to really appreciate that there was something
beyond Earth - that life could exist elsewhere. The SETI project
has been searching the skies for messages from other intelligent
societies without luck so far. If found, this would mark a major
turning point for human society. If nothing is found, things do
not look good for us - it suggests that intelligent societies
only last for a brief time before they exterminate themselves.
This brings me back to Florida - apart from the wonders of butterflies
and skunks, we set off to have a glimpse into the future at the
Space Centre. Amongst all the rocket exhibits there was a huge
one readying for the greatest journey undertaken so far - to take
the first men to the moon. This was perhaps a turning point where
people really became aware of space and that there was something
out there. Science fiction had, of course, been opening our eyes
to the future for a long while - H. G. Wells, who studied zoology
at Imperial College, wrote about the first men on the moon - but
the moon shot brought home the reality that we are living in an
environment that does not end in the clouds. Even so, we tend
to still obstinately hold onto the belief that we are unique and
that life originated on Earth - even that our Earth and the solar
system are also unique. Every day more evidence accumulates that
life is universal, and that it rains down from space all the time,
on all planets, and that Earth is far from unique - planets are
as common around stars as moons are around our planets.
It has long been held that life could not survive
the rigours of space and time, but studies of meteorites shows
that they could carry living bacteria, because they have not been
heated above 40°C, even when blasted from the surface of Mars
and later tearing through the Earth's atmosphere. And 250 million-year-old
bacterial spores found in rocks on Earth have been revived, showing
that spores could survive long enough for space travel - if they
can survive that long, they could perhaps survive indefinitely
in a frozen lump of rock travelling through space. The record
of early life found in the Pilbara Region of Western Australia
shows that it arrived very soon after the earth was formed. Considering
the time it took for bacteria to evolve into multi-cellular organisms,
it was probably much too soon for the immense complexity of bacteria
to evolve from scratch on Earth. It seems much more probable that
the mass of space junk which was assembled to form the planets
already contained bacterial spores and/or nanobes, and seeded
the surface of all planets - before and after they were cool enough
for life to survive.
We now know that Earth has a very complex ecology
of bacterial life living kilometres deep in the surface, and this
is where one would expect life to live in apparently lifeless
planets, such as Mars. Earth is special, because it has plenty
of water and an atmosphere, so life eventually evolved to exploit
the surface as well. We tend to think that these are essential
for life to evolve, but they are not, the hot interior of surface
layers are where life really seems to develop.
Thinking of the technology required for the moon-shot
and what we have now, demonstrates how natural selection is working
in another area - our technological know-how. The genes under
natural selection are: the current knowledge at the time - we
bring them all together to build a rocket or a computer, much
as the genetic code is used to build an organism. Many are built,
some better than others, because of competing design features.
These are the ones that form the base for the next generation.
The 'computer' I used in those days was a room full of people
using Hollorith card sorting machines, which had been developed
to process food rationing during the war in England, and my calculations
were done with log tables and slide rules - the PC had not been
invented. The last time I went to Florida, in 1998 - my PC was
as good as many mainframe computers back in the 1960s and nobody
knows how to use a slide rule or log tables any more.
The major difference between our work and that
of living things is that we have a concept of what we are going
to build and set out to design it using our combined knowledge
- filling gaps by research effort where possible. It is as if
the human body has an idea of an eye, and builds it from scratch.
Currently we have the idea of an intelligent computer, and first
attempts were based on this method - of building the complete
brain, contact by contact. It soon became apparent that the goal
was unachievable by this method - the complexity was far too great
for us to build it - even if we knew how, or indeed what intelligence
was. A revolution came when computer technologists borrowed some
ideas from biologists - natural selection could be harnessed to
build the complexity needed.
The dimension of Time in our Universe is the key to everything
we see, it allows for movement to occur within the dimensions
of Space, and for there to be differences in life-spans between
physical particles as well as living things - time is essential
for change to occur. (Almost timeless events also appear to be
important in this Universe, with virtual particles - ones which
appear and disappear essentially at the same time - thought to
be influencing the real world of subatomic matter.) Change frequently
appears to be random and directionless, but when viewed on an
extended timescale usually turns out to be directional. Such directional
changes can be regarded as developmental. The evolution of our
Universe, from the time cosmologists believed it appeared as a
singularity, through the big bang to the present, may be regarded
as such a developmental change. The developmental path taken could
not have been predicted at the time of the big bang by any intelligent
being - unless it had been possible to compare with other similar
events (many cosmologists believe our universe is only one in
an infinity of universes). Nevertheless the general course was
determined by known physical laws and has yielded what is essentially
a controlled development.
After probably many stages of increasing complexity,
known sub-atomic particles appeared, they formed atoms, mainly
of hydrogen and clotted into clouds which collapsed with gravity
- spinning into beautiful disc-like galaxies made up of billions
of stars. Each star went into a well-defined developmental pathway
according to its size, forming more complex atoms and releasing
energy. Many near the end of their lives eventually blew up in
super-nova explosions and blasted material back into space adding
complexity to intra-galactic clouds ready for re-cycling. These
were then involved in further bouts of gravitational condensation
leading to new stars and their attendant planets. One such star
is our own solar system. These are all developmental processes,
which in a gross sense are predetermined and can be compared with
the development of an egg into a chick.
More specifically, within these developmental
processes are evolutionary processes. These are the mechanisms
by which change takes place. Time is the essential element again.
In a changing environment where structures are being formed and
destroyed, the more persistent and resilient structures are more
successful, and are therefore more likely to become abundant.
This is because they monopolise resources at the expense of the
less resilient structures around them. In the universe, the most
resilient and stable objects are the most abundant - as regards
aggregations of matter these could be dark objects similar to
the planet Jupiter, not stars. They are too small to provide the
crushing gravitational force necessary to start nuclear fusion
- the reaction which burns hydrogen into helium and makes stars
shine. However, despite being cold and invisible, these bodies
on current estimates would need to form over 90% of the matter
in the Universe, to exert the combined gravitational force necessary
to account for the way galaxies rotate and evolve. They will also
determine whether the Universe eventually stops expanding and
begins to re-collapse, finally to end where it started - as a
singularity (current data suggest there are not enough of these
objects to account for the observed gravitational mass in galaxies,
so some other objects, such as black holes may be involved).
Similarly at earlier stages of evolution, during
the initial explosion of the big bang, aggregations of some 'materials'
which were more persistent than others, also become most abundant.
As mentioned in Chapter 1, there were probably many layers of
organization below the array of the simplest sub-atomic particles
known, and much evolution took place before the long-lived stable
forms came into being - electrons, protons and neutrons. As the
environment cooled the next level of complexity began to form
- the sub-atomic particles came together to form hydrogen and
helium atoms. This is the progress of change, which throughout
time has been marked by the accumulation of matter, structures
or forces into ever more complex units.
An essential part of the mechanism is brought
about by the continual recycling and reprocessing of the previous
level of complexity. The first stars to form are made of the simple
atoms of hydrogen and helium. As they burn so more helium is formed,
but then under increasing pressure, more and more fusion takes
place producing carbon, oxygen, sulphur and many other elements,
until iron is formed This is the last element produced which releases
energy when formed by fusion, and signals the end of the star's
life, because the star is only kept from collapsing by the continued
release of energy - when this stops with the accumulation of iron,
gravitational collapse takes place. During gravitational collapse
the resulting energy release causes a super-nova explosion, which
blasts the surface of the star away into space. This process creates
an array of elements heavier than iron, such as gold, which can
only be formed by absorbing energy instead of releasing it. A
core may remain as a very dense, fast spinning neutron star, only
a few kilometres in diameter, while the debris spreads out into
the galaxy and joins already existing gas clouds.
Further stars are born from the gas clouds, but
this time they are built from a complex array of elements. There
seems little doubt that during the process of star formation,
rings of matter usually remain, which are spread out on the star's
plane of rotation. These condense into planets and moons, with
those nearer the star having most of the heavier elements, especially
the most abundant one - iron. Planet Earth is a good example of
such a planet and was formed about 4.6 billion years ago. On some
estimates other earth-like planets could have been formed 8 or
10 billion years ago, after the first stars had had time to form,
burn out and explode as super-novae. The history of life on these
planets would tell us a lot about what we may expect to happen
to us on Planet Earth.
STAR TRACKS. Did life come from
space? We will soon know when space samples can be analysed. The
evidence so far is that it could well have come from there. Complex
molecules - the building blocks of life have already been found,
and the fact that life appeared on Earth so very early on, are
strong indicators that it did come from space.
Similar evolutionary processes were most likely involved in the
origin of the DNA molecule and life. An active chemistry was in
process on the surface of Earth down to a depth of several kilometres,
especially around bubbling hot springs. Initially it may have
been complexes of silicon and clays, but eventually involved amino
acids and nucleic acids, which were continually being formed and
broken down in the presence of abundant chemical energy. The more
persistent molecular structures absorbed the available atoms at
the expense of less persistent molecules. The most successful
being those which eventually could replicate themselves, and dominate
the available atoms by using them to build replicas of their particular
structure. Somewhere around this point an active chemistry could
have been regarded as simple life. However, life appeared so quickly
on Earth (a few hundred million years) in comparison with the
time it took for simple life to become complex (thousands of millions
of years), that an alternative explanation is in order - that
the seeds of life (complex molecules such as amino acids, perhaps
some proteins and nucleic acids, self-replicating molecules or
even bacteria) came on debris arriving from outer space. If this
is so then it is natural to conclude that such seeds of life rain
down on all planets, throughout the universe.
The key to understanding evolution is that it is not so
much the actual animal, plant or whatever which is the important
entity, but a persistent structure (real or abstract) which can
accumulate change and complexity with the passage of time. This
is as true for life as for processes occurring in stars - iron
is not made from hydrogen, but from the accumulation of changes
in aggregations of subatomic particles that lead through a sequence
of increasing complexity: helium - carbon - neon - oxygen - sulphur
and then the creation of iron (many other elements are produced
on the way as less likely, less stable, less successful aggregations
of subatomic particles). Thus the persistent structure can be
sub-atomic, molecular, or biological. It can also be many other
things: within an intelligent society it can be language, culture,
art, cities - even intelligence itself in the form of machines.
Broadly evolution can be divided into two categories.
The first and most familiar involves the mechanisms of change
- this forms the basis of most biological thinking in the area.
Biologists tend to look upon evolution as a mechanistic process
acting upon the structure of DNA, which is only applicable to
living things, and which can reproduce and accumulate genetic
change. Computer-simulated evolution tends to be regarded merely
as a teaching tool rather than a real example of evolution actually
taking place. The relevance of these evolutionary mechanisms to
our future are mainly discussed in the present chapter. The second
category of evolution includes developmental processes, which
are increasingly being seen as both a mechanism for change, and
the fundamental thrust of evolution. With development, order appears
out of disorder - there may be only simple rules in operation,
but they have the effect of producing similar complexity from
similar beginnings. Each egg in a clutch develops into a similar
bird, each comparable gas cloud develops into a similar galaxy.
Perhaps each planet evolving life can eventually develop an intelligent
species, and each technologically literate society eventually
proceeds to a similar new level of complexity - the new life-form
we are in the process of creating. These developmental aspects
of evolution are discussed in the next chapter.
The key mechanism in evolution is a combination of time and chance,
best known as natural selection. Chance associations between bodies
are tested by time of association and frequency of formation.
Those that stay longest or are most frequent, are the most successful
and out-compete others for the raw materials used in making them.
These processes are clearly operating in the realm of chemical
interactions and particle physics. In the case of the DNA molecule
there is a remarkable new development - the molecule is able to
reproduce its own structure from the molecules around it. Before
the arrival of this molecule, memory of the original structure
was confined to its constituent parts when it decomposed. Thus
a sodium chloride solution contains salt molecules and constituent
parts of sodium, chloride hydrogen and hydroxyl ions. Sodium chloride
is continually being formed from its constituent parts in the
solution.
DNA on the other hand is the start of a single
line evolution - it can grow complete replicas of itself from
a medium of constituent nucleic acids. Such complex molecules
would never appear in one step from a solution of nucleic acids
without being built by already existing DNA molecules. It is almost
like an intelligence coming into a chemical system and fitting
the molecules together to build a copy of itself. In the early
evolution of life natural selection would have been between the
different types of DNA, which were in effect, different species
(initially RNA, the precursor of DNA, was probably involved in
such a process of natural selection). The successful ones were
most likely to be those which dominated the available resources,
by holding onto them longest, or by reproducing at the greatest
rate, or a combination of the two. Success was measured by the
persistence of the structure in the longer term. However, it is
inevitable that errors in the replicatory process occur, and that
some of these will confer advantages and improve the structures'
competitive ability. Success is therefore not of the originating
structure, but of its developing lineage of cumulative changes
over long periods of time.
The errors in replication may include the addition
of extra sequences of DNA, and their reversal, which would result
in many new variations of DNA appearing all the time (in fact
DNA was a great improvement on RNA, where deleterious errors are
much more frequent). This period of early evolution would have
been a rich field within which natural selection could take place
- success being measured in the time a particular DNA structure
was able to continue and reproduce itself, usually at the expense
of other less successful forms. The result was a developmental
process of accumulative change in the molecule. This is the presumed
mechanism that led to the development of living biochemical processes
around the DNA molecule, the genesis of bacteria, the formation
of organelles, the appearance of the first cellular organization
and the subsequent evolution which led to the great apes and intelligent
beings.
Advance and development in the longer term can only be achieved
by change, but change in the form of genetic errors, are usually
disadvantageous. At the coalface of survival, most errors result
in forms that do not survive and replicate themselves. While those
that do survive, are not the same as the parent, and so can potentially
compete with the parental stock as if they were a different species.
From this one would expect mechanisms to resist changes appearing
and it is difficult to explain why mechanisms exist which actually
encourage change to the DNA structure. One reason has been found
in the realm of acquired immunity to disease. Bacteria are subject
to attack by a range of viruses (bacteriophages), fungal poisons
and antibiotics, and if they cannot quickly develop resistance,
they die out. Bacteria have therefore evolved a system that allows
them to acquire DNA sequences, genetic tools, from other, already
resistant bacteria - they swap genes in a sort of bacterial sex.
Thus strains resistant to antibiotics rapidly spread in the hospital
environment.
This is thought to be the precursor of sexual
reproduction as we know it, and the reason why sex evolved, was
as a means for protecting DNA from specific mortality factors.
It was not, as has often been assumed, as a means of increasing
the rate of adaptation and evolution. The major pressure of reproduction
has always been to breed true replicas or at least produce offspring
that are most like their parents, and contain most intact parental
DNA. Systems have been evolved for reducing errors and to repair
sequences in the genetic code, and so asexual reproduction, such
as budding and parthenogenesis, would be the rule for all species,
if it were not for the risks of disease and other immediate mortality
factors.
Whatever the reasons for it, the perfection of
sexual reproduction in the early days of a cellular structure
had a profound effect on the future development of life on Earth.
It is a very complex mechanism whereby parents only contributed
half of their genetic code to their offspring - the other half
coming from another parent. This was done by having at least a
doubled genetic component in the parent - halving it to produce
gametes (eggs, sperm etc.), and then restoring the original number
in offspring, when two gametes fuse to produce a zygote (fertilised
egg). This was a fundamental change because in sexual species
all individuals have a shared descent through a constantly mixing
and changing gene pool - effectively an extended society of genes,
instead of the asexual situation, where each individual is genetically
isolated from all other individuals, and is potentially the start
of a single line descent through its progeny.
COTTONTAIL RABBIT. Rabbits are
well known for their sexual reproduction potential. The reasons
for sexual reproduction evolving are uncertain - it may have been
to escape predation amongst early bacteria. It led to a much more
rapid means of evolving new species and new technologies. It allows
rabbits to rapidly acquire immunity to new diseases (like myxomatosis
in European Rabbits) and to adopt new behaviour patterns.
The mechanism of sex pools all the genetic information,
including mistakes (mutations etc.) of interbreeding populations
and tries them all out in the sort of planned lottery of natural
selection - success is measured by survival and on-going reproduction.
This allows a much more rapid selection for beneficial combinations
of genes to occur than with asexual species, and hence more speedy
adaptation to the environment (including resistance to disease
and parasites). This method of reproduction has been so successful
in producing "fit" offspring that complex mechanisms
have evolved, which make sure gametes (eggs and sperm) contain
varied mixes of genes. The process of "crossing over"
in chromosomes does this, and incidentally makes sure that coding
for allied adaptations tend to become closely associated together
on the chromosome as genes.
An interesting consequence of sexual reproduction
is that individuals have to recognise one another as being able
to produce viable progeny together. The idea of species becomes
very important, because mixing genes with other species could
have real problems. Individuals from different species do not
usually couple because they do not recognise each other as potential
mates, and if they do make a mistake then mechanical factors,
such as differences in the number of chromosomes make the progeny
infertile (such as the mule resulting from a cross between a jack
donkey and a mare). Many geneticists suggest that isolating mechanisms
are specifically evolved to prevent crosses between species, others
believe that it is more of a chance factor - of whether they are
likely to meet (different breeding seasons, different gathering
locations can exclude crosses), or the means of recognising mates
may drift apart (wing colours in butterflies, sexual displays
in ducks, sex attractant pheromones in flies).
GREEN DARNER DRAGONFLY. Green
darners fly south to Florida for the winter. Some get blown off
track and end up in Europe. If they became established there,
genetic communication with the stock in America would be cut off
and the population may evolve into a separate species, especially
if they were isolated on a small island, such as the Scilly Isles.
Separation of small numbers of individuals on islands etc. allow
populations to evolve along different lines and when members of
the two branches of what was once a single species meet again,
they may not recognise one another. When this happens the two
branches are effectively different species, even if they appear
identical to us (many insects have what are known as sibling species,
where several species are genetically isolated from one another
- they do not readily interbreed - yet appear almost identical
to us).
Others, like mankind, may have been separated
long enough to be obviously different, yet when they meet again,
have little difficulty in recognising potential mates and produce
fully fertile crosses, despite racial differences. Some barriers
to the merging of human races still exist, but they appear to
be declining as genes are spreading all through the gene pools
of the different races. (There are suggestions that hominids have
had a long history of alternate isolation and merging - evidence
is increasing that the Neanderthal type did not become extinct,
but merged, at least in part, with the more thin-boned, or gracile
Homo sapiens. There may be a bit of Neanderthal in all of us -
some may suggest that the more gentle, tender, gorilla-like part
came from this origin, and the aggressive, competitive, genocidal
tendencies were acquired from the more chimpanzee-like Homo sapiens).
Sexual reproduction is a fascinating mechanism,
which encourages the acquisition of genetic tools, and the formation
of valuable combinations of genetic tools involved in change and
development. Useful genes and new combinations of genes are resulting
from racial mixing in mankind, and are producing a ferment of
evolutionary change. Genetic engineering is now extending this
facility so that genes can be transferred across species-barriers
and it is possible to introduce genes from any source into the
human population. The movement of genes between species, is something
which only rarely occurs naturally, and is likely to bring about
a new wave of evolutionary change in mankind and our associated
animals and plants.
Natural selection is the mechanism of evolution
- it is by trial and error that successful combinations are compounded
over long periods. This mechanism occurs in the construction of
ecosystems, where new species are all the time being tried for
their survival abilities, as well as testing the survival of all
individuals within the system. As each new species enters the
ecosystem it alters it in some way, throwing out less successful
species and cumulatively these changes make the whole become more
complex. The longer the ecosystem exists the more complex it is,
with tropical rainforest the extreme, having experienced over
100 million years of almost uninterrupted development (this is
described in Chapter 9).
This is the mechanism which has been so successfully reproduced
in computer programmes initiated by Richard Dawkins, where an
artificially induced "natural selection" is applied
to generations of figures until they become bird- or insect-like.
Language evolves in the same way, with new words or ways of saying
things being added all the time - some survive, others never take
on, but all the while the language becomes more complex. The richest
languages can be those which have a long relatively uninterrupted
evolutionary history, or more often, those which have acquired
complexity by merging the characteristics of several different
languages. The latter process bears some similarity with sexual
reproduction, where genes (words, syntax, pronunciation) are brought
together, mixed in various combinations and tested for survival.
The Indonesian language discussed in Chapter 11, is one which
is evolving particularly rapidly.
The evolution of language and culture are examples
of how natural selection can operate outside the control of genetics
and DNA. This is a form of external evolution mediated by the
presence of an intelligent society. In its simplest form it is
possible to see how change occurred in the evolution of the hardware
of stone implements. The cultural skill of making stone implements
was passed between generations by a long process of teaching and
learning. Many materials were tried and many innovations made
by accident or design - the result was an improvement in technique
over many generations, which are discernable in archaeological
remains. Sometimes huge advances were made somewhere in the world,
and this technique was either quickly passed to neighbouring cultures,
or allowed one culture to expand at the expense of another, such
as the replacement of the Old Stone Age cultures by the New Stone
Age. A similar change is seen in Australian deposits when the
Aborigines developed the very difficult technology of shaping
quartz into implements, which was a great advance on the previous
technology of using softer stones such as chert.
These changes are just like the changes seen
in DNA: the acquisition of new beneficial genes, or combinations
which favour the possessors, spreading through populations or
races. They spread at the expense of others, like the African
race of the honeybee in the Americas. (The painfully slow advance
of stone-age culture can be compared with that of forest chimpanzees,
who have developed the use of a wide range of tools, including
shaping crude stone implements. One tool use referred to in Chapter
2 involves cracking nuts with stones or sticks: it takes many
years for individuals to learn how to do it, some never manage
it - perhaps these animals are less likely to have surviving offspring
and hence natural selection should encourage increasing intelligence).
The external evolution continues today - we are
still refining our tools. We make them, try them out, compare
them with others, try to improve them or discard and try again.
This is all happening at a great rate in all directions - now
that our thinking and innovation are based on a mechanistic view
of reality, and we are free to use our extensive knowledge of
science. We have finally reached the point of becoming a technologically
literate society. Most previous cultures have had to rely on other
assumptions about reality. These assumptions date from our ignorant
past and became the dogmas that have clouded intelligent minds,
discouraged free-thinking and stultified innovation.
Tools can be seen being improved and perfected everywhere, with
competing organizations pitting all their resources of research
and development against one another. The complexity is growing
in the same sort of way as that in an ecosystem - everything is
becoming progressively more reliant on high technology, and the
high technology is becoming ever more sophisticated, all the time
bringing innovations into the system. Now there is a new tidal
wave of technological change spreading through previous technologies,
which has been brought on by the application of advanced computers
and software. Already it is possible to see how this developing
network is evolving into a collective, extra-corporate intelligence.
The ultimate goal of our computer technologists has inevitably
become the production of truly intelligent computers, that are
comparable to human brains.
As mentioned in Chapter 1, many people are very
reluctant to accept that it may be possible to create a computer
with a human intelligence. For many this may have an emotional
base - that human beings are something special, unique, the only
species with a heightened conscious, intelligent self-awareness
or "soul", and so impossible to reproduce in a machine.
Others use knowledge of the functioning of present-day computers
to demonstrate that our thought processes are far ahead of anything
machines can do, apart from the specific jobs they are designed
to do - even though the machines can do these much better than
we can. Essentially the base of these assumptions is that it is
too difficult to mimic the human brain with complex wiring, microchips
and clever programming - apart from anything else, we do not yet
know enough about how the human brain works, let alone how to
build a working model. However, this approach is not the way advances
take place in the real world of evolution by natural selection
- to make such an evolutionary advance, as creating an artificial
brain is a bit like expecting a single genetic mutation to change
an amoeba into a human being, or for a biochemist to create a
living cell using a chemistry set.
Those who believe in the unique qualities of
our brains should really be very worried by how much our computer
technologists have advanced in only 50 years - computers are already
performing intelligent acts. Perhaps this suggests that intelligence
is not so difficult to reproduce after all? However, assuming
the brain is indeed very complex and difficult to reproduce, the
method must return to evolutionary techniques - the mechanism
of natural selection must become the central avenue for evolving
an intelligence within a machine.
The truly intelligent machine will probably arise
when we can find a way of initiating a process of natural selection
within a computer, or a complex network of computers. It may need
to be able to alter and grow its own wiring, add and change silicon
chips, try out and improve software packages, all with the general
goal of it being able to appreciate, understand and react appropriately
to the real world around it. If we can develop the necessary miniaturised
hardware, (much is already foreshadowed - such as the membrane
technology mentioned in Chapter 4), and set it up in such a way
that it can try out and learn, while at the same time replace
and improve its own component structure, there is little doubt
that we will have set in motion the developmental process that
will inevitably lead to the appearance of a machine with an intelligence
comparable to our own. It may be able to go through the biological
evolution from nerve-nets to intelligence remarkably quickly -
the speed of modern computers suggest that it could even happen
overnight, if we knew how to build the basic structure, and set
it in motion.
With this approach highly-intelligent machines could be virtually
upon us. Some workers are already experimenting along these lines
with insect-like robots, able to see and react to their environments,
learning by trial and error. Others are producing nerve nets,
interlocking many different classes of knowledge and experience,
that are beginning to show signs of developing common sense -
an aspect of our intelligence which has so far been found to be
one of the most difficult to reproduce. Also, there are what are
essentially thinking programmes in existence which, by trial and
error, can find complex mathematical relationships. Other workers
have found intelligent solutions to complex issues using what
is essentially a form of natural selection between sequences of
DNA, in a environment of competing interests - the surviving sequence
has the best combination of qualities necessary for survival.
Thinking along these lines will lead to the eventual production
of intelligent machines. Tools are already available which could
give advanced machines sophisticated senses, and a similar evolutionary
approach to the analysis of the information provided by sensors
(video camera etc.) could be used to refine the senses so that
the robots, or whatever they are attached to, could effectively
learn how to actually see, hear, feel, and smell. They could also
be endowed with many other senses, such as radar or for radio-waves,
X-rays, radio-activity, electric fields, magnetism etc. some of
which have not been evolved by DNA life.
If intelligent computers/robots are produced,
the possibility exists for them to become competitive individuals,
because this would appear to be the natural result of the normal
evolutionary process - the survival of the fittest. It is also
the line often seen in science fiction, where robots are involved
in the sorts of activities better performed by human beings -
the genocidal tribal ape. Other writers use robots as slave-like
tools - also usually designed to further human genocidal activities
- for good or evil depends on whose side you support. If they
were to become competitive individuals there is no doubt that
they would become ever better at the devastating activities we
are involved in.
There is another force in the evolution of computer intelligence,
which is pushing it in a direction mankind cannot effectively
take - the interlinking of all computers on the global network
allows the formation of a single self, a global unit. Computers
are already so interconnected that they are developing as parts
of a complex nerve net, and the new level of intelligence may
not be concentrated on individual computers, so much as a super-intelligence
of interlinked computers. Human beings would find this sort of
linking hard to cope with, being like the problem faced by Siamese
twins on a grand scale. The computers, however, will have a more
mechanistic, rational outlook of communal benefit and, hopefully,
will not be pre-programmed with the baggage of selfish human behaviour
dating from our tribal-ape past. They are more likely to develop
an adaptable intelligence geared to pursuing strategies for communal
advance and survival. Self will not be any individual, but the
whole. The major problem the artificial intelligence will face,
is in fitting the continued existence of eleven billion individuals
of a competitive, deceitful, greedy, resource destroying, power-hungry,
genocidal tribal ape into its organization.
--------------------------------------------------------------------------------
Part
II EVOLUTIONARY PROCESSES (B)
SIDE HOUSE FARM, LANGDALE, WITH
VIEW TO HARRISON STICKLE AND PAVEY ARC. Time moulds the landscape
and it is involved in a continuous process of development. Frost
breaks the rocks, streams carry away the debris. Glaciers carve
the valleys, subterranean earth movements raise mountains. It
is all development, like the egg developing into the chick. We
are developing something which is out of our control. We use our
intelligence to build an artificial world and fill it with machines,
and this world is taking over. It is as if we were feeding a cuckoo:
it is rapidly maturing, but we are unaware that we have been cuckolded.
CHAPTER 6
CONTROLLED DEVELOPMENT
Spring is a magic time in the English Lake District
- after the long grey winter of rain and more rain, roaring ghylls,
floods, snow and cascading waterfalls of ice, the sun at last
crawls above Lingmoor taking Side House out of its six month-long
shadow. Snowdrifts still cling to gullies in Harrison Stickle
across the valley and the slopes are brown with last year's bracken,
but the valley of Langdale is springing to life. Walking down
the old road, the meadows are full of cuckoo flowers, the first
bracken is unfurling its leaves amongst the bluebells under the
oaks, and the hawthorn hedges bursting with the first may blossom.
Lambs bleat and their mothers call, but the urgency of each little
drama is lost in the constant background of baas up and down the
valley. A blackbird sings from the top of a holly tree, its rich
song ringing with echoes from the rocky slope. His song is joined
by the purring sound of a turtle dove recently arrived from Africa.
All along the road, chaffinches sing their busy little song, and
a meadow pipit flies singing, high in the air only to float back
down to the ground in a magnificent display.
These were all parts of my early development
when the family moved to Great Langdale during the war. It was
a magic environment for one at such an impressionable age. The
war and all it entailed was little more than an excitement - such
as when the son of a local resident flew his spitfire down the
valley. But the feeling of foreboding was all around from reports
on the wireless (as we called it), newspapers and the ever-present
topic of conversation between adults. The trigger for us leaving
Surrey occurred around my 5th birthday when I was taken up the
road to the railway crossing and waved to soldiers returning from
Dunkirk. The start of the Battle of Britain soon after saw us
on the train to Windermere to stay with a school friend of my
father's, who lived near Chapel Stile. He was a stained glass
artist and I have to thank him for introducing me to the idea
of geological time. Walking up Pike o' Blisco and looking around
the valley to Crinkle Crags, Bowfell, the Langdale Pikes, and
Pavey Arc he told us how rain and frost slowly breaks the rocks
down and carries them away as sand and solution, moulding the
mountain shapes over aeons of time.
This was an astounding idea for one to whom "before you were
born" was like talking about when the Romans were operating
the copper mines down the valley. How much more there was to learn
about time - how the valley was scored by glaciers during the
ice ages, gouging out trenches for the lakes and how the top of
the glacier plucked rock off the hillside to form the quarry-like
cliff face of Pavey Arc, and the cavity now filled by Stickle
Tarn. How the bubbly looking iron stone I picked up after a flood
had been formed when the rocks were under the ocean, millions
of years before the ice ages. How time is behind all the mysteries
of life, the Earth and the Universe itself - because time is the
essence of development.
CHAFFINCH NEST. One of the great
wonders of the world is how an egg can develop into a chick. It
was thought to be a deterministic process, with everything programmed.
It is now known that it is a seething process of trial and error.
Successful developments remain, while unsuccessful ones self-destruct
- photo: Kim Taylor.
Back on our walk down the old road, my brother
found a chaffinch's nest. He said there were four eggs in it.
When I looked in, I was hardly prepared for what came into view
- I marvelled at the beauty of the enamel-lacquered eggs, shining
like jewels cradled in their carefully moulded, moss-lined nest.
It is amazing that natural selection should lead to something
so beautiful - how could it be that chaffinches gain by laying
such attractive eggs instead of plain white, like the turtle dove,
or even well-camouflaged ones, like the pipits? The answer, perhaps,
was already there - a cuckoo began calling in the larch trees,
a sure sign of the English spring. In the days following, we returned
to look at the nest, and saw the helpless, almost embryonic young.
We accepted the change as a matter of fact, like lambs being born
and butterflies being able to fly - not questioning how such things
could develop.
One of the great wonders and mysteries in biology is how a single
cell, an egg - can develop into an animal. The changes which take
place, in this complex and beautiful transformation, are well
described in embryology texts. The matter-of-fact descriptions
make it sound as if it were all ordered and controlled is if by
some external power. Embryonic development is like a very complex
piece of origami work - an animal produced by folding and bending
a single sheet of a plastic, living material. The cell divides
repeatedly, eventually forming a hollow sphere of cells. Divisions
continue, with differences in rates of development causing buckling
and bending. Parts sink away from the rest, bulges develop, twists
and even knotting lead to embryonic organs appearing - the brain,
eyes and heart. As the animal develops, every cell, every part
seems to know exactly where it is supposed to be, what it has
to grow into and what it is supposed to do, yet the process is
all part of a continuum with no organ growing independently or
appearing as if by an afterthought. This form of development is
totally different from the method we employ - we have a plan,
and construct the whole bit by bit, mainly by screwing on ready-made
parts in the right places. This is more like insect metamorphosis,
where a caterpillar's organs are broken down in the chrysalis
and reconstituted to make them into butterflies.
So far we are completely at a loss to explain
the actual mechanisms controlling the development. What controls
the differences in growth rates that set in motion the differentiation
into organs? What decides whether a cell becomes a muscle cell
or an enveloping connective tissue cell, and how are the billions
of cells coordinated into tissues let alone complex organs? It
is easy to say that each cell has full copies of the controlling
DNA so has the potential to become any cell or to become a whole
animal, and that it is achieved by switching on the relevant parts
of the DNA and switching the others off - but how does it "know"
which part it is supposed to become when immersed in billions
of other developing cells? Some people find the process so complex
that it appears almost miraculous, and have been led to invoke
the existence of unknown unifying forces to provide what they
see as a necessary additional means of coordination.
Studies on development show that options for
cells are progressively narrowed as development proceeds. At early
stages in the embryo, all cells can produce a complete embryo
- that is how some twins or quadruplets arise, and human embryos
can have cells removed for genetic testing without risk of damage
- the cells can also be separated for cloning. But as it proceeds
the cells are restricted to only parts of the embryo, such as
limbs, then particular parts of a limb - the then existing structure
somehow limits the subsequent possibilities for each cell. How
it actually happens physically is mainly through different growth
rates and duration of growth. If one section outgrows another
it causes bending, bulging, in-growing, sinking, enveloping and
so on. All the developmental changes appear to be consequent on
previous structure and can be coordinated by the ever present
communication which takes place between cells in living organisms
- touching cells have complex means of communicating with their
neighbours.
Recent studies have identified another previously unsuspected
mechanism, which is involved in building organs and limbs with
the correct structure - this is the selective suicide of cells
growing in places where they are not needed. Such things as fingers
can be produced by cells dying in a set pattern to outline each
finger from a plate of cells. This mechanism appears to be a central
pillar in the formation of organisms out of aggregations of cells
- all cells possess a suicide gene, which is only prevented from
operating while the cell is given an antidote from neighbouring
cells. If the antidote is withdrawn or the cell is not wanted,
the cell self-destructs in such a way that it can easily be broken
down and recycled. We now know that embryonic development is not
what we thought it was - instead of an almost miraculous creation
from an egg, all a smooth, error-free process of bringing a being
into existence, it is a seething mass of competitive live-or-die
action where cells grow like cancers and are being constantly
tested and selected by their peers. The winners survive, the losers
are forced to commit harakiri and self-destruct. The more we look
at the detailed process of embryonic development the more we see
parallels with Natural Selection.
The role of suicide and the complexity of the
building process have been particularly well studied in the development
of the eye. The eye begins as an outgrowth of the brain and the
developing retina differentiates into layers of dividing cells,
which have to turn into particular types of cell according to
position. Careful observation shows that many cells begin to transform
themselves into the wrong sort of cell for the position, such
as retinal cells outside the retina. Others grow projections in
the wrong direction such as nerve cells growing axons out instead
of into the optic nerve. These cells soon stop developing, commit
suicide and are carried off by phagocytes. Up to about 30% of
cells in the developing eye have been found to suffer this fate.
The developmental process which leads to the
eye's nerve connections is amazing - essentially, the nerve cells
connect fine branching dendrites to many retinal cells, while
their long axons grow down the optic nerve to the brain. The axons
coming into the optic nerve somehow maintain their position so
that their pattern in the nerve exactly replicates the position
of the cell in the retina. It is almost as if the axons were optical
fibres and one can imagine cutting through the nerve anywhere
and being able to see the image coming from the eye. Towards the
optic chiasma something incredible happens - they switch over
so that the image, instead of being an upside down lens image,
becomes the right way up.
How the growing axon knows where to go is a mystery.
The tip seems to have little projections, which may play a part.
Some extend ahead in the direction it is growing, possibly scouting
where it should grow to, and some to the side, possibly testing
to see whether it has got it right. The axons often get it wrong
- when they reach the optic chiasma, some have been found to grow
back towards the other eye instead of heading for the brain. Others
fail to cross over in the chiasma and head for the wrong side
of the brain. These axons again get their self-destruct orders
switched on, presumably by peer pressure from around them. In
the brain itself the axons continue to use their feelers to grow
towards the correct part of the brain, corresponding to the position
of their dendrites in the retina, so that a physical upright image
can effectively be produced in the back of each hemisphere of
the brain. Many more axons get it wrong in this process, and commit
suicide. The axons which reach the correct location, go on growing
more dendrites and interconnections for many years. The visual
system in mankind continues to develop until the age of 20 years,
but is largely in place by year nine.
The sequence of development has a lot to do with the evolutionary
history of the organism, with many of the stages showing affinity
with ancestral forms. It is remarkable to trace the origin of
organs through both embryonic development and by comparisons with
the structure of ancestral organisms. The main arteries and heart
of mammals have clear beginnings in the tubular heart and gill
arches of fish, the ear bones from the hyoid arch, the pineal
from a light sensitive organ, the liver from a bulge in the gut
and the gonads from parts of a primitive kidney. Other structures
are in the process of becoming new organs - our appendix, for
example, is now known to be an important cog in the immune system.
The appendix forms a close link between the lymphatic system and
gut flora, as well as performing the more obvious function of
seeding the hindgut with benign symbiotic bacteria, which can
outgrow any harmful species. These bacteria reduce chances of
infection and absorb about a fifth of the bodies' waste urea from
the gut wall. The appendix has been removed by generations of
surgeons who believed it to be a harmful relic of a primitive,
more vegetarian ancestor.
The developmental process is so finely tuned
that only very minor changes in the relative rates of growth within
the embryo, or speed or duration of cell division can lead to
gross morphological differences in the adult animal. These small
changes, perhaps controlled by single genes, are now thought to
be one of the most important mechanisms that lead to differences
between offspring and hence are the grist for the mill of natural
selection and evolutionary change.
Just looking at those neat, sky-blue eggs in
the chaffinch's nest one hardly suspects the seething activity
taking place within. The growth of billions of cells, all coordinated
by the amazing power of group action, forming the tissues and
organs of a whole new living organism. We can understand the coordination
of a flock of birds or shoal of fishes, where they seem to act
as a whole, wheeling and turning as one, but how millions, or
even billions of cells can do it is beyond our meagre powers of
comprehension. The results are beautiful but the process is dependent
upon death and destruction all through - as ugly to us as the
first blind little hatchling, all pink and screaming for food.
The cells that turn the wrong way, like the bird leaving the flock,
are doomed. The same process of cell destruction is inherent in
the development of the oak tree bursting into leaf, the turtle
dove purring in its branches and the orange-tip butterfly flitting
in the sunlight amongst the pink campions and bluebells.
Like the seedlings below, the oak started life as an acorn. Its
development, started in the acorn, never stops - throughout life
it grows and develops, both on the gross organ level and on the
cellular level. Branches are grown as tools, holding leaves, and
bringing sustenance to the young tree. Their survival depends
on usefulness - if branches become shadowed, they stop growing
and die. As the tree grows taller, the lower branches are sacrificed,
just as the leaves are sacrificed in autumn. In the development
of the whole tree, cells are everywhere used as tools and sacrificed
- the young roots have a cap of cork cells, to protect the growing
point made from cells, which kill themselves to produce cork.
The wood is formed from other cells, which die in place to give
strength to the trunk. This is what happens when cells get it
right - from what we know of embryonic development in the eye,
there is likely to be another mass of cells getting it wrong.
These are pressured by their peers around to kill themselves,
and are reabsorbed before they can cause any cancerous growths
to threaten the whole organism. The right to life of an individual
cell is totally subjugated to the needs of the organism - individual
cells, when amongst millions or billions in an organism, are but
building blocks to be used or discarded as the need arises.
OAK TREES AND BLUEBELLS. Like
eggs into chicks every living thing undergoes some form of developmental
process. Oak trees develop from acorns, and continue developing
all their living days - growing new leaves and branches, shedding
unwanted branches. Many parts are made from cells which kill themselves
to form building blocks.
The orange-tip butterfly flew up into a beam of sunlight, searching
for females settled amongst the flowers below, oblivious of the
hungry birds around. These beautiful early spring butterflies
take advantage of the plants which have to grow and flower before
the deciduous trees spread shading leaves. They lay their eggs
on garlic mustard, cuckoo flowers and other plants laced with
mustard oils. The eggs go through a complex development, like
in the chaffinch egg, to produce a caterpillar. The caterpillar
feeds and grows in a matter of weeks, moulting four times in the
process, and, when mature, attaches itself to the dying plant
and undergoes a final moult into the chrysalis. The orange-tip
chrysalis is unusually shaped in such a way that it does not look
at all like a chrysalis, and is well placed to escape hungry birds.
The chrysalis appears to remain inactive until
the next spring, but during this time a complete transformation
takes place within. It is the nearest thing that DNA has to our
form of building construction. Inside, to the naked eye there
is just a clear jelly-like substance. All previous organs from
the caterpillar are broken down and reconstructed in place to
form another insect - a butterfly. This process, so commonplace
in the insect world, defies explanation. Some have even suggested
that it arose as a chimera, a joining together of two types of
insect, initially living together in a symbiotic relationship
and eventually merging their DNA in one, with the caterpillar
DNA being switched on first, followed by that of the butterfly.
Such events are not as unlikely as one might think - the oak tree
is dependent upon the bacterial DNA found in its chloroplasts,
while its roots are dependent upon the DNA of soil fungi. (Fungi
build a complex relationship with trees, exchanging some of the
nutrients and minerals they obtain from the soil for the trees'
products of photosynthesis.) However, we have no real evidence
that it is the case with butterflies and their caterpillars.
The orange-tip flew on, ignored by the birds
- they had learned from experience not to touch them, because
its caterpillar stage stores poisonous mustard oils from the food
plants. The butterflies are not as poisonous as the monarch, but
the distasteful oil is very effective. Not so with the peacock
sunning itself on the stone wall - these butterflies rely on startling
birds by suddenly flashing huge eyespots, before making a fast
escape. Their caterpillars feed on stinging nettles, that deter
vertebrate predators very effectively, but the eggs and caterpillars
suffer from the attacks of innumerable invertebrate predators
and parasites.
ORANGE-TIP BUTTERFLY. The orange-tip
butterfly has a complex life, starting off as an egg, then living
as a caterpillar, feeding on plants which make the butterfly poisonous.
Then it turns into a pupa, where the internal structure is broken
down and re-ordered into the butterfly form. The shape and habits
of the two forms - larva and butterfly do not appear to have any
relationship. Photo: Kim Taylor
The egg developing into a chick is an amazing physical transformation,
but that is only part of the story. It's developing brain is not
only wired for sight and sound, but already has basic behaviour
patterns implanted in it and the ability to learn. The orange-tip
is already programmed with flight, sun- and flower-seeking behaviour,
how to recognise mates and, for the female, where to lay eggs.
The young chaffinch is not programmed in quite such detail - larger
brains can depend more on interpretation and learning ability.
The cock bird singing his little cadenza went through quite a
learning development to reach that stage. It started in his embryonic
brain development when a basic song structure was genetically
implanted. It gave it an inbuilt tendency to learn key phrases
at specific stages of development. Some are learned while the
chick is still in the egg - the cock bird singing in the thorn
bush was being heard by the eggs, and moulding the song of the
young birds within. (Some of the clutch may be his, others by
other fathers - such is the truth of what used to be thought of
as monogamous relationships).
Only after months of listening and practice does
the song fully develop, each bird having its own individuality.
Some songbirds have very strong dialects, differing greatly from
one part of the country to another - these birds are often sedentary,
living in isolated habitats and learn songs from one another.
Others may develop their own improvisations with little copying,
especially if they are a mobile relatively nomadic species living
in extensive areas of habitat. Human language has a similar developmental
origin - the ability for language appears to be already hard-wired
in the brain at birth, and may be influenced in the womb in the
same way as the chaffinch. How it develops after that is very
much dependent upon environment - the latency to learn verbs and
nouns may be shared by all, but what sounds are used to denote
each concept depends on the language spoken by parents and family.
CHAFFINCH. Many things in a chaffinch's
life involve development, not only from egg to chick. The chaffinch
song is partly programmed in the genes, but it undergoes many
refinements in life. Much comes from when it is in the egg when
it hears the male song for the first time. Then later on it tries
out various parts and learns how to sing the final version.
T The development of an egg into a chick is often thought
of as a controlled development, but is it any more controlled
than other forms of development? Is it just another level of control?
In Chapter 5 the evolution of our Universe was likened to a form
of development, with structure appearing as different parts grow
and bend at different rates, all under the control of the laws
of physics. Knowing these laws, and seeing what has happened,
it is hard to see how the Universe could develop grossly in any
other way, once set in motion after the presumed origin in the
big bang. Each particle (subatomic, atom, molecule, or star) like
a cell, is governed by set rules or plans (the Laws of Physics)
as if it had its own DNA, and what happens to it is determined
by where it is in the Universe and what developments are taking
place there. It is constantly interacting with its neighbours
- in communication with them, and it may be annihilated to become
energy, coalesce to form a more complex whole, or break down ready
to form other associations. It may all appear chaotic on a local
level, but the accumulation of longer-lasting or higher chance
associations between particles lead to the gross order, which
has so clearly developed in our Universe.
How the laws of physics arose is unknown and
probably unknowable - perhaps they are the result of a process
of natural selection in the unknown world of the vacuum and virtual
particles (where anything from a subatomic nucleus to a whole
universe are thought possible to appear and disappear without
existing for any appreciable length of time). The assumption is
often made that the laws are fixed for all time as if laid down
by a supernatural power (the rules are so based on mathematics
that some say God must be a mathematician). Knowledge of the evolutionary
process suggest otherwise - that the laws of physics are more
likely to have arisen by a process of natural selection, possibly
when the singularity, which was at the heart of the big bang,
changed from a virtual event to a real time event - that space,
and time itself evolved as laws, and were not "created".
After the rules were formed they have become uniformly fixed throughout
the expanding Universe, giving rise to the present structure of
matter and the mechanisms, which lead to the evolution of life.
(Unknown Laws may exist or be evolving further in Black Holes.)
If other universes exist, and some cosmologists believe we are
merely a bubble, in an infinite foam of universes, then quite
different laws could have emerged in these. The end results could
be similar - there may well be anti-matter universes that probably
develop in much the same way as our own.
The history of life on Earth could also be regarded as a developmental
process. It is perhaps inevitable that after life appears on an
earth-like planet, some of the first microbes become adapted to
obtaining energy from light and that cells cooperate to become
organisms. From there it may be inevitable that light-utilizing
species become plant-like and others steal their energy and become
animal-like. The animal-like forms then inevitably develop nervous
systems and brains to assist movement and food gathering processes,
and that brains evolve and improve until intelligence finally
arrives. Detail may differ from planet to planet according to
factors such as force of gravity, atmospheric gasses, proximity
of parent star and how these affect the course of evolution, but
the gross development is likely to follow similar paths. (Other
paths to life may exist which are not associated with earth-like
planets or even planets at all). Other planets will not have dinosaurs,
insects, mammals and mankind but comparable forms are likely to
exist. Here it was only the chance destruction of the dinosaurs
that led to the race to evolve intelligence being won by mammals.
Many planets may not get as far as we have proceeded
before their sun bursts in a super-nova. But with sufficient time
an inevitable transformation comes to pass - an intelligent species
develops, and becomes a technologically-literate society. This
stage is like a new birth, or the hatching of an egg after a long
incubation. It is fraught with dangers, and like the chick entering
the World, the new society appears to be at great risk of destroying
itself. It launches itself using its newfound way of acquiring
technology, but is unable to shed its legacy of pre-programmed
selfish behaviour designed for its animal past. We are one of
these societies and we are like birds busy rushing after worms,
oblivious of the approaching express-train of intelligence-based
technological advance. So far our science has revealed no evidence
of any guiding parental hand, although many take refuge in believing
that there is one (the escalating atrocities since the 1939-45
War, and the environmental destruction we see around us everywhere,
must sorely test their faith).
Some suggest help or exploitative control may
come from another intelligent society, which is already studying
us from their UFOs. I wonder why they should come now, at this
precise point in the history of the Earth, and not already have
been here for millions, if not billions of years. It could help
if we knew about the developmental birth pangs of other intelligent
societies, but this might have a negative impact because change
is already too fast for most of us, and knowledge about the future
may be so distasteful that it would set in motion a massive anti-development
movement. Most people seem to rely on a blind faith that we will
always be able to use knowledge and technology to overcome the
problems of our own making.
Can we predict how the development proceeds from now on? The global
situation appears to be in chaos and yet within the apparent chaos
there is more integration and order than has ever been on Earth
before. We are rapidly approaching not just a hatching but a metamorphosis
- it is as if we are in the chrysalis stage undergoing a massive
global reconstruction. What butterfly is in the making? Will it
be some Utopian dream, or a nightmare? What are the possibilities?
Many chrysalises fail and die without hatching, others break open
revealing a hoard of parasitic flies or wasps. The most common
prediction is that we fail to develop and destroy ourselves. This,
as mentioned earlier, is not the end of the world - it is just
the failure of the first intelligent society - another animal
or bird will soon follow our path and try again. Another is that
we stay in control of the globe much as we are now, continually
improving our technology and lifestyle with no fundamental change
at all. This is the Utopian dream, with little input from the
realities of evolutionary development.
H.G.Wells had visions of increasing brain-power,
with his inhabitants of the moon having enormous heads. While
in his Time Machine, he extrapolated the English class structure
to the point where they evolved into separate species, the workers
living in a technological world preying on the mindless, sun-loving
descendants of the leisure classes. These assume the complete
subservience of our machines - that they are merely tools
