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Moving Beyond Darwin


As many of you will know I have been investigating evolution somewhat extensively for a little over two years now. I have always had the unshakeable feeling that there was something wrong with our perceptions of evolution, but since biology has been my 'neglected science' up until this point, I haven't really been in a position to expand my viewpoint until now. I once said that I felt the modern view of evolution explained matters of biology as well as Newtonian physics explained the physical world. Asymmetric Biscuit countered that, to a reasonable degree, Newtonian Physics was a good approximation for the physical world. Two years later and I can confidently report that Newton fudged his results to get his version of gravity accepted by the Orthodoxy. It is fair to say that for terrestrial engineering, Newtonian gravity suffices. But in evolutionary biology, where the battleground is largely ideological and not pragmatic, the Orthodoxy's rigid adherence to neo-Darwinian beliefs seems less acceptable. Indeed, with Darwin's as its spokesperson, the Orthodoxy's stand seems primarily a religious (or faith-orientated) stance. Science, or at least the patient, agnostic investigation of what passes for reality (which is what I hope science represents), has very little to do with what the establishment attempts to pass off as truth.

So what am I about to say? That Darwin was Wrong? Of course not. He was no more Wrong than he was Right. He had an idea, a brilliantly insightful idea, certainly, and an idea that has helped many other people have brilliant ideas. But Darwin's idea no more perfectly explains biological life than Pythagorus or Euclid's ideas perfectly explained mathematics. It was the first step on a long road. I'm going to tell you my current version of that road on the understanding that this is just my perspective. Walk the same path and you may well see different things. But this is what I see.

In the beginning...

Let me take you back, back to the distant past, to the Land Before Pubs. Back before that first lucky hominid inhaled the sweet marijuana smoke for the very first time - back before even multi-cellular plants existed, let alone hemp plants. Indeed, back before life as we perceive it existed at all. The Earth is young and, frankly, we know absolutely nothing about it. We can make some guesses, but that's as far as it goes.

We don't know how life began. We probably never will know. Likewise, we will probably never know if terrestrial life started here on earth, on Mars or in the deep voids of space. One thing I can say with confidence is that at this point in time, all these possibilities and more are viable. It is fair what Margulis says, that moving the origin of life off the planet doesn't get us any closer to solving the question of how life started, but frankly the evidence at this time no more points to Earth than it does to space. The origin of life remains no more than a question of faith.

However, it seems probable that the first step towards life was some kind of self-replicating chemical construct. Once such a chemical existed it would only be a matter of time before all available raw materials in the putative primordial soup would be converted to this replicator. Once you have self-replicating chemicals, the way is open for more efficient replicators to develop, and certainly as time goes by, these replicators have the opportunity to become more complex. Ilya Prigogine, a Nobel prize winner who for once almost certainly did deserve praise, showed how increasingly complexity was an almost inevitable by-product of dissipative systems (such as living organisms) which means essentially that whilst the rules of thermodynamics instruct everything to turn to shit, life is playing by a subtly different set of rules.

So we have our so-called prebiotic replicator, and somehow, by some mechanism, we end up with a genetic code. Probably a whole set of different genetic codes, actually, but somewhere down the line we get DNA and RNA and the raw materials of life as we claim to know it. Most of this early view of life is undisputed in so much that no one has anything but broad guesses as to what could or might perhaps have happened.

And here comes our first break with Orthodoxy. The establishment claims that whilst the creation of self-replicating molecules is monstrously unlikely there were enough random encounters between chemicals that it became highly likely, if not inevitable. Fair enough, as a belief. But one can hardly claim that such an approach is any more sound than claiming that God, Goddess, Whimsy or Magic caused the origin of these molecules, because either way the hypothesis is untestable and comes down to what you, the individual, choose to believe.

I personally believe that it makes no great shakes as to how we choose to see the ball being set in motion. What's far more interesting is the fact that we are here now and able to waste our time speculating about such things, if we choose to.

Unwitting Co-operation

Somehow, we get to the earliest single celled organisms. Whatever else we can say about them (and we can't say much with any confidence) they were good custodians to the planet. They looked after it for four billion years without batting an eyelid, because quite frankly, the first eyelid wouldn't evolve for quite a while.

I suppose the Orthodoxy's view of this time before multi-cellular life was a host of different competing organisms, savagely fighting for the available resources and with only the strongest surviving. Eventually the fist single celled organisms were so advanced that they became multi cellular and took the battle onto a whole new playing field.

Nothing could be much further from the apparent truth of the matter.

Firstly, nothing short of Divine Intervention could have created the cells from which all multi cellular life springs using just the Darwinian mechanisms of mutation and natural selection. Even the Orthodoxy has been forced to concede this (although like all defeats, the news is slow in travelling). The biological requirements for multi-cellular life are such that randomly shifting nucleotides is just not enough to make the leap. Later, we will look at just what was required to make that advance possible at a cellular level, but first we have to look further afield.

Biologists, generally speaking have been reluctant to pay attention to the atmosphere, despite the fact that nearly all life depends on it as a complex conveyor belt of raw materials. Interestingly, geological evidence suggests that the composition of the modern atmosphere is essentially the same as it has been since the early days of life. The reason this is so interesting is that the composition of the atmosphere, whilst apparently stable, is a long, long way from equilibrium.

In case I am losing people's attention, let me restate that as follows: if all life on earth was somehow made extinct, say by a drunken God, inadvertently pushing the biological self destruct button, the atmosphere would very rapidly change a very different mixture of gasses. The only reason the atmosphere stays the way it appears to be is the action of the biosphere (and some related processes) constantly removing some gasses and pumping others into the air.

I won't dwell on this for too long, because if you are interested you should go and read Lovelock, who knows the material far better than I do and writes with both charm and insight. The bottom line is that one thing that had to happen in the four billion years before multi cellular life began to flourish, was the establishment of a homeostatic control mechanism that could regulate the environment and keep it within tolestable limits. Lovelock calls this mechanism Gaia.

Dawkins calls Gaia "wrong and dangerously wrong". I find his attitude surprising and disappointing. Homeostatic control mechanisms - such as that which keep your body at a constant temperature - certainly evolved in multi cellular life. It is not at all clear to me why anyone should consider a large collection of unicellular lifeforms, to be subject to wholly different rules to multi cellular life, except that the former has even more room to maneuver.

No one is claiming that the organisms that first came together to make Gaia were aware of how their co-operation was creating a stable environment for life. It is merely the case that whatever helps life persist will in turn be encouraged to persist, just as implied by Darwinian natural selection.

And despite Dawkin's religious protestations, the geological, atmospheric and biological evidence points unerringly towards Gaia. Without it, even the small yet steady rise in our suns out put of radiation would have rendered the earth a lifeless rock many aeons ago. Without it the build up of certain gasses would have made multi-cellular life impossible. When Lovelock first proposed Gaia in the 70's it was just an insightful hypothesis attempting to explain some pretty gigantic gaps in our knowledge. Today, Gaia theory sits proudly at the forefront of the rising tides of ideas that marks the gradual infiltration of the Orthodoxy by the new, more holistic approach to science.

I will take a moment to explain why this essay seems to be attacking Dawkins so resolutely. It is important to understand that the Orthodoxy, being essentially a power block of old ideas, has surprisingly little variety in its perspective. Because of this, any one spokesman is as good as any other. Since Dawkins willingly accepts the mantle of the currently retiring paradigm, I have no qualms at directing my criticisms towards him as a representative of that which will eventually fade into history and obscurity.

The Earliest Communes

With Gaia in place - a huge selection of different organisms and processes that, through changes in population and similar mechanisms regulate the terrestrial environment - multi-cellular life was a possibility. Animals, as we know them, require a high level of oxygen in the atmosphere to act as fuel for their high-octane metabolisms, but the oxygen could not be allowed to rise too high or everything not underwater would be wiped out in a spectacular conflagration the moment lightening first struck.

The stage was set. But our actors were still just single cells. 'Hamlet' one suspects would be less impressive if performed by bacteria.

SET, or Serial Endosymbiosis Theory, has struggled for acceptance for much the same reasons the Gaia theory has. Anything that even remotely resembles holistic thinking has been anathema to the currently retiring paradigm. However I am proud to report that all but one of SET's claims has now been grudgingly accepted by the Orthodoxy, and Margulis remains by her own admission stubbornly optimistic that its final (and from my perspective, least important) claim will eventually be vindicated.

It intrigues me, but does not surprise me, that Margulis has been involved in two of the scientific theories at the forefront of the new paradigm, Gaia theory and SET. Call me a sexist if you will, but women strike me as far less likely to get trapped in the closed minded territorial tub-thumping of Dawkins' Neo-Darwinist fundamentalism. I have high hopes that this new paradigm will finally put pay to the hideous old boys club that served so effectively to keep women out of scientific research in the nineteenth century and before.

But what is SET, and why is it so important to multi cellular life? In essence, what it claims is that the components of eukaryotic cell (those cells that make up multi-cellular life) are the product of symbiosis between single-cellular components that were to become the nucleus, the ribosomes and the mitochondria. They started out as single celled organisms in their own right and ended up inside the cells of modern life, possibly as a result of a failed attempt at digestion.

SET is practically unrefuted at this time (although the issue of whether flagella are also the result of endosymbiosis remains a live one). Every cell in our bodies is the modern descendent of the earliest communes in existence, and just as Gaia represents macro-symbiosis, SET represents micro-symbiosis. It is becoming more and more apparent that the history of life is not just the story of competition between differing life forms but also of co-operation.

The co-operation of the separate organisms that make up eukaryotic cells provided the raw materials for life to go multi, so to speak With function differentiated inside the cell, each cellular component could become more efficient at what it did, because it could rely on its allies to carry out those tasks that it wasn't good at. So mitochondria concentrate on being efficient at handing energy whilst the nucleus learns how to store protein designs safely, and to co-ordinate the construction of these proteins.

Now we have a stage, some actors and (for those who choose to believe in such things) a director. All we are missing is a script.

The Impotence of Being Earliest

The earliest multi-cellular fauna we know about are found preserved in Pre-cambrian strata and are known collectively as Ediacara. They appear essentially to be large, hollow pancakes, with very little differentiation. We don't know if their cells were eukaryotes (i.e. cellular communes) or not, but we do know that they didn't last long, geologically speaking. If they represent multi-cellular life's first script, they are more an episode of 'Days of Our Lives' than a 'Hamlet'.

A lot of questions remain unanswered about both this early experiment in Growing Big and the more successful experiment to follow. I am particularly interested in how cell differentiation came about. Without it, you couldn't be made of bone, muscle, blood, brain and the other components that make up how you are. Without differentiation, you would presumably be a hollow pancake just like the Ediacara.

In essence the problem is the issue of design. There is little doubt that DNA represents the blueprint for all the proteins in an organism. But one cannot build a house from a list of building materials. A plan or design of some kind is required. I am greatly troubled by my inability to find any evidence that the Orthodoxy has taken this issue seriously. They just seem to assume that the DNA does it somehow. If this is the case - that the establishment view rest purely on assumption - then it is a deep embarrassment to a supposedly scientific perspective.

Informally, I was able to convince myself that it was theoretically possible for an organism's design to spring from the result of a branching instruction, coded in the DNA implicitly. But I could not find any evidence to support this hypothesis. Indeed there is more evidence to support Sheldrake's suggestion that an animals shape is controlled by morphic fields than to support the purely reductionism approach.

Not that I am saying Sheldrake is right. We just can't be sure right now. But as I said to Fibonati Butterfly once, his work is most valuable because he is asking the right questions. Sheldrake, of course, has a very holistic perspective on biology, but it is important to understand that just because the new paradigm is open to holistic approaches doesn't automatically make holistic approaches True. Indeed, the two cornerstones of Sheldrake's work appears to be explicable by epigenetic programming (a recently discovered Lamarlian inheritance mechanism) and by whatever mechanism is found to underlie psi effects.

Nonetheless, it is fair to say that Sheldrake was influential in reopening the issue of Lamarkian inheritance (the idea that changes to an organism can be passed to its offspring). In that area, his courage has been an asset to the research community, especially those outside of the narrow confines of the Orthodoxy. There is now little doubt that there are Lamarkian inheritance mechanisms that supplement classical Mendellian inheritance and allow organisms a greater degree of adaptability to changes in local conditions on time scales too short for conventional evolutionary mechanisms to operate.

To return to the point in hand, it is not at all clear how organisms end up the shapes they do, and neither is it clear how the early cellular communes developed the ability to take on these shapes. The one thing that is clear is that as soon as life learnt how to do it, there was no turning back.

Lights! Cambrian! Explode!

The Cambrian explosion, as it is affectionately known, is the name for an extraordinary period of time roughly 545 million years ago. It is so named for the profusion of life that seemed to just explode onto the scene in what is (in geological terms) just a clock tick. Thanks to the infamous (to paleontologists at least) Burgess shale, we have a surprisingly detailed record of early multi-cellular life.

We will probably never know what bridges the gap between the first eukaryotic cells and the fauna found in the Burgess shale, but we can speculate. It fascinates me that there should be such variety of body plans in such a short period of geological time. It implies a rate of change vastly more rapid than any other that the fossil record points to.

Perhaps multi-cellular life occurred simultaneously from many different sources (which makes sense from the perspective of Formative Causation/morphic fields, but makes very little sense from an orthodox perspective). Perhaps the early co-ordination mechanisms were so sloppy that early organisms just couldn't reproduce accurately, and random design was the order of the day. Perhaps some condition that triggered multi-cellular life somehow triggered the change in many different eukaryotic cells at the same time. We can only speculate.

When I first came to look at the Burgess shale, I had been told that there were a vast array of different body plans, far more than exist in the modern world, and this intrigued me, as I have always been suspicious of the apparent lack of variety in the general design of creatures. Why should bilateral symmetry be so universal, for example? (Bilateral symmetry essentially means that an organism has a line of symmetry from head to tail - which if you think about it is true of the vast majority of multi-cellular organisms that are capable of movement).

Fibonacci Butterfly suggested that bilateral symmetry might be an inevitable part of design for an organism that moves; ingest food at one end, excrete waste products from the other. Very convenient as you can then move towards food and away from your own waste. I would tend to agree, but since bilateral symmetry was already the norm by the time of the Cambrian explosion I have to be sceptical about this idea.

Given the rapidity at which bilateral symmetry became the norm (bearing in mind that there are many other ways of putting together a hypothetical organism, including radial symmetry such as in starfishes and asymmetric plans, as in plants) I have to question any appeal to Darwinian issues in the establishment of bilateral symmetry as a prevailing scheme. Dawkins would claim that bilateral symmetry represents such a good engineering solution that it was inevitable that it would predominate. But one has to ask how we know it represents such a good engineering solution, and Dawkins answer would be that it must be a good solution because it predominated so rapidly. Having reduced his reasoning to a mere tautology, we have no choice but to reject it, at least on scientific grounds.

I have met the same argument when dealing with convergent evolution in other places. The Tasmanian wolf is almost identical in design to other canines, including the domestic dog. And yet the Tasmanian wolf is a marsupial, genetically removed from dogs and their kind by such a huge degree that they are effectively not related at all. (And there are many other examples of convergent evolution, such as ichthyosaurus and dolphins). The Orthodoxy's attitude seems to be that there must be a limited number of solutions to the problems of animal design and hence it is not surprising that many animals find the same solution. This is not wholly implausible, but it is entirely unsupported by any evidence. One might just as well say that Goddess/God/Aliens designed the genetic code to produce such similar animals for some spiritual purpose. It argument would hold about the same weight.

Someone once said to me, as I was arguing that there were important questions to be resolved regarding convergent evolution: "But convergent evolution does happen." This is a wonderful statement, because it seems to miss the point entirely. Of course it happens. We can see that it happens. But that doesn't put us any closer to understanding why it happens.

I have no solution to this question of bilateral symmetry, although I feel it is a highly relevant one. If the Orthodoxy's assumption about body designs resulting directly from DNA is validated at some future point, perhaps it will be revealed that bilateral symmetry is the most information efficient way of designing an organism that is going to move. Who can tell? For now, the issue is an open one.

The importance of the Cambrian explosion, in my opinion, is twofold. Firstly, the person who discovered the soft-bodied fauna completely missed their relevance and tried instead to classify them in terms of modern animals. One can hardly blame him. He was unable, as so many scientists are, to see his find in any terms other than those he had been taught and had lived with comfortably for so long. What a mental breakthrough it must have been to suddenly realise that what he had discovered was something that completely overturned conventional thinking on life! The Burgess shale represents a wonderful illustration of how excessive belief in the currently orthodox ideas can block the acceptance of ideas that more accurately model what we choose to call reality.

Secondly, the Burgess shale represents reasonably convincing evidence that the classical Darwinian perspective of survival of the fittest is erroneous. Why? Because no-one, not even the most learned biologist, could look at the fossils of the Cambrian explosion and say with any confidence which species were destined to evolve into modern life, and which were destined for extinction.

Experts have been able to identify which species were the likely ancestors of modern life, and they look no better adapted to their environment, or superior in any other sense, to many of the other forms around at the same time. Indeed, only the tiniest fraction of the body plans around in Cambrian times survived to the modern day. And as far as we can tell, more by luck than by superior design.

The message from the Burgess shale appears to be quite straightforward. Evolution is not a record of Progress (as was believed for quite some time - and indeed, is still believed in some camps) but a record of the adaptations made by various creatures to survive at various times, and who survived to the present day in part by a whole lot of luck.

Gould talks of the Wheel of Fortune as a metaphor for the way that many species become extinct - extinction by lottery. Whilst some are no doubt made extinct by competition from better adapted organisms, the vast majority die out for no reason other than random chance. With this in mind, any idea of evolution as a line with single celled organisms at the bottom and man at the top is insane and ridiculous. Our position is no more privileged than any other life form around at the moment. Our chief difference seems to be that we have evolved a sense of arrogance far outstripping the rest of nature.

Where Did All the Giants Go?

I find it curious that all the truly gigantic animals have become extinct. Whale sharks and blue whales aside, modern life is practically miniaturized compared to the standards of the Mesozoic (crudely, the Dinosaur Era). We all know the Big Lad dinosaurs like tyrannosaurus rex, and apatosaurus (you may know it as brontosaurus), but if you have a good look around you'll find huge birds, giant snakes and enormous sharks have all gone by the wayside. (Megladon, a shark the size of a whale, makes the great white shark look literally like small fry by comparison).

All extinct.

Now you may wish to claim that these animals were just not efficient, or that they were out-competed or something similar. But the fact is, the environmental conditions than existed in the Mesozoic were essentially identical to modern conditions. And these creatures existed for millions of years, with substantially no changes at all if the fossil record can be believed. Megladon teeth, for example, are one of the most abundant fossils around.

I would hazard a guess that the reason that there are no giant creatures around at the moment does not represent the superiority of 'smaller' animals, but merely the prevailing trend for the current conditions. People often forget that the environment that an organism adapts to is made up not only of the inanimate, but of all the animals that co-exist with it. It seems plausible to me that the web of Mesozoic life supported these giant predators, whereas our current days where speed rather than size seems to be more important cannot support such giant animals.

But times will change. At some point, the playing field will shift again and no-one can say what will predominate when it does. This is one of the great messages of evolution, that what dominates now will likely be extinct at some future point.

Take one of my personal favourite animals, the ammonite. These nautilus-like creatures dominated the oceans in the Mesozoic, but when the Cretaceous came to an end, they, like the dinosaurs, were wiped out. I have seen no better explanation for the extinction of these shelled creatures beyond bad luck. The asteroid impact at the end of the Cretaceous (an event for which the geological evidence is now hugely in support of - the iridium deposits found in post-Cretaceous strata lack any other reasonable explanation) may well have been the cause of the mass extinction that robbed the world of the dinosaurs and the ammonite.

The ammonites gave way to the fishes. Not because the fish were superior, but because the ammonites were unlucky. That seems to be the way it goes.

I recently discussed with Jehanine the issue of punctuated equilibrium, the theory proposed by Gould and Eldredge which suggests that rather than a steady, continuous process, evolution is marked by periods of stasis (in which very little evolutionary change occurs) followed by sudden periods of change. Animals alive today owe their survival only in part to superior adaptation, and to a very great degree to being damned lucky.

After much investigation, I can only conclude that Gould and Eldredge have hit the nail on the head. At this point in time, the only problems against punctuated equilibrium that I have heard occur when someone tries to use classical evolutionary reasoning to explain something that now seems far more complex than simple Darwinian reasoning can deal with.

For example, a sensible complaint (raised by Jehanine) is that punctuated equilibrium implies evolution only takes place at certain points in time, whereas as we understand the Darwinian methods, it should be taking place constantly. This is a reasonable question, and like many reasonable questions it exposes the problems in orthodox thinking.

Darwinian thinking goes something like this: organisms mutate, superior organisms thrive, inferior organisms die. Hence, evolution constantly improves organisms, adapting them to their environment. This view in the extreme is what is known as adaptionism.

However, let us take task with the first point, that organisms mutate. I am prepared to accept that there are indeed methods by which changes to organisms occur (after all, evolution is dead in the water without it). But despite the Orthodoxy's claim, no evidence exists that new genetic variation occurs spontaneously. Although we have seen natural selection at work in our time, we have only seem selection work on genetic features that were already present.

For example, most people know about the moth that, with the advent of the industrial revolution, began to be increasingly found 'dressed' in black rather than its natural beige. The black moths could hide on the soot-caked trees and walls of the post-industrial world better than the beige moths, and hence had a selective advantage. However, the genes for the black colour were already present in the moth. The genes did not evolve in our time.

Indeed, there is a substantial problem with evolution by mutation, in that 99% of mutations (or more) are detrimental to an organism's chances of survival. Most mutants die. The Orthodoxy responds by claiming that, yes, most mutants die, but over the time scales of evolution enough mutants occur that a small number are 'fitter' and hence survive. There is nothing wrong with this argument, but there is no evidence for it.

Conversely, there is evidence that natural selection actually slows the rate of change in genetic material. This apparently contradictory claim was first suggested by Kimura, and has since been demonstrated almost undeniably to be true. The rate of change of nucleotides in the parts of DNA which are not expressed (intron DNA) compared to those parts that are involved in coding proteins used by the animals (exon DNA) is radically different: and it is the introns DNA which changes faster.

It actually makes a lot of sense. If most mutations are detrimental, then most changes to exon DNA will cause the creature to be inferior and hence to be less competitive than its non-mutant peers. Conversely, changes to introns produce no effect to the individual creature and hence the rate of change of sequences in intron DNA can be much faster than in exons where the watchdog of natural selection limits the amount that the code can change. It is called the Neutral theory of genetic change, and it has been broadly validated by research.

In fact, I even have a hypothesis as to what the 'purpose' of intron DNA might be. Viruses occasionally copy sections of DNA to different parts. Often these changes are dangerous or fatal, but at times the substitution effectively codes for a new and exciting protein. This may well have happened recently (geologically speaking) with the Antarctic cod. Genetic evidence suggests that its 'anti-freeze' glycoprotein occurred as a result of a transposition of intron DNA into an exon. Given that intron DNA can mutate far faster than exon DNA, it seems plausible to me that evolutionary novelty might happen as a result of intron DNA's freedom to mutate. I call this the Cut and Paste hypothesis, but at the moment I have no way to test it. If this hypothesis is true, intron DNA is a requirement for genetic novelty.

Moving back to the central issue of punctuated equilibrium, I do not find it at all hard to accept that evolutionary change is 'stifled' during long periods of history. This is, after all, exactly what is shown in the fossil record. The Orthodoxy explains the same evidence by saying that there are many other animals, but they just aren't recorded in the fossil record. (This is a bit like saying that the accused's finger prints are not found at the crime scene because the accused never touched anything whereas everyone else touched everything constantly). There are going to be gaps in the fossil record, that is unavoidable, but one cannot deny that many animals span a vast period of billions of years in the fossil record.

One can suppose that once a set of organisms have evolved into a reasonably stable set, the 'room to maneuvre' is so low that change can only happen on the most gradual of time frames. However, after a mass extinction, a whole new set of rules apply. The extinction of the dinosaurs and their kin made way for mammals to have a shot at being the top predators. Throughout the Mesozoic they had been tiny little scavengers, eking out an existence in between the lumbering thunder lizards. At the end of the Cretaceous, the rules changed and mammals got their turn at bat. Presumably, somewhere down the line, something will take out the mammals and give some other type of animal a chance.

It occurred to me, as I was coming up with the Cut and Paste hypothesis, that after a mass extinction, the pressure of natural selection should actually be reduced. With the well established predators gone (dependent as they are on the food web underneath them), organisms that previously would have been too poorly adapted to survive suddenly have a chance to show their stuff. Dawkins' metaphorical ratchet is off, and for a brief period of time animals have far greater freedom to change.

This, for me, is quite a compelling argument towards punctuated equilibrium. Because when we look through the fossil record we find rapid change in the animals recorded in the fossils only in two types of place: one, at the boundary points representing mass extinctions (where the rules of the game were suddenly changed), and two, at the Cambrian explosion (where the rules of the game were being made up as life went along).

Changes do occur in between these times, stasis is not total, after all, and evolution still works in the long stretches of time in between. But the most radical changes to life happen in the wake of the mass extinctions, when life has a chance to make up a whole new set of rules. In our case, we've come into the game at a time when giant animals are no longer as effective as once they were. Who knows what the life that follows us will find?

As a final point before I put punctuated equilibrium to one side, it is worth understanding that if major changes in life can only come about by mass extinctions, then we may owe our much-vaunted intelligence in part to the fortuitous position of Jupiter and the asteroid belt, the arrangement of which causes asteroids to be thrown repeatedly into the path of the Earth. Perhaps this arrangement constitutes an 'evolutionary pump', shaking up the status quo frequently enough for evolution to achieve far more than it could in a state of constant stasis.

Then again, if it wasn't for Jupiter drawing away many of the comets from the Oort cloud from the Earth's surface, we might have impacts so frequently that life would never actually get much of an opportunity to recover from the devastation and we might have no multi-cellular life at all. We can only speculate.

And so... the Present

And so I have followed evolution from its shaky beginnings, through its dodgy middles and now to its uncertain present. There are many questions that remain to be answered - more than I can elucidate in a short article such as this one. However, from careful analysis of the competing views I can only conclude this:

Evolution consists of a large number of tools, of which mutation and natural selection represent only one perspective. As well as the classical Darwinian and Mendellian processes, contingency seems to be a major theme of evolution, and life seems to utilize a high degree of symbiosis on both a macro and micro scale, as well as using other mechanisms such as epigenetic inheritance which we have not even begun to fully investigate. It is far too premature to assume that we have found even a fraction of the answers to the questions that Darwin first raised.

I will leave you with one final thought. If you are not yet convinced of the importance of symbiosis to the history of life, consider that mammals are only able to give birth to live young by virtue of a viral invader which has integrated itself into our genetic make up. When you see a foetus develop, it is surrounded by little viral allies which do not harm the developing organism but rather have made live young a possibility by breaking the ties with the embryology of the past.

Competition may be part of life, but it is not the whole of life. Dawkins' "selfish gene" metaphor may be a useful tool for allowing us to reason outside of the narrow confines of humanocentric thinking, but it does not follow that selfishness is the guaranteed norm. Indeed, without symbiosis, multi-cellular life simply could not exist. And I cannot help but find it ironic that whichever way you look at the "selfish gene", life breeds out pure selfishness: any creature which cares only for itself must surely die out. Dawkins may see an organism sacrificing itself for the survival of its young as selfishness, but from the point of view of the organism I can see only altruism. An individual gene, after all, codes only for protien and is scarcely in a position to do anything but persist if it happens to be useful.

In this, as in so many things, it comes down to which metaphors you wish to use, and how you wish to look at the problem. I now look on the current world genome - the complete set of all the different genes in use by organisms today - as a record of those genes which helped propagate life up to this point. Some of those genes may have principally benefited just the individual organism, and some may have contributed to wider mechanisms. But ultimately, all we can say about the genes in the world today is that they made it here somehow.

And what more can you say about humans other than that, somehow, we made it here.

- SL