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Wednesday, 29 September 2010

Just A Quick Note On Evolution

Just wanted to get this out in public.

In looking into evolution and such I've been able to make a connection that I think is quite important.

Evolution isn't linear, or at least, anything like as linear as it should be, according to a classical Darwinian account.  Some species have extreme stability over very long periods of time when the habitat around them changes wildly.  A very extreme example of this would be the alligator, which exists in its present form in the fossil record something like 37 million years ago.

That's through a lot of ice ages, and a lot of change, but the organism stayed static.  Now that's just one example, and an extreme one - but the stasis of species through changes in habitat, just in general, is a head-scratcher for evolutionary biologists.  It is pretty common, and indeed, the norm.

And then, every now and then, there is a kind of period known as the 'evolutionary leap' where an organism undergoes rapid change - or a new family of organisms come into being simultaneously.

They all have similar ancestry, and have clearly passed through a process of evolution, but the time is strange.

Everything is either too slow or too fast.  Things are too static, or too volatile.  And this is the exact thing that the connection I was able to make addresses.  Mercifully, it's very simple, and makes clear predictions of the fossil record, so can be clearly falsified if wrong.

This all centres around what's called, in biology, the 'unit of selection'.  What is the core unit that evolution works upon?  Is it the group?  Is it the individual?  Is it the gene itself?

The thing is that the unit of selection idea has been applied in quite a linear way.  That group, individual, and gene are linear progessions downward in terms of scale.

What I propose is a lateral movement.  Instead of looking evolution from the perspective of the group, the or individual, or the gene, why not look at it from the point of view of the beneficial mutation itself?

To actually make the beneficial mutation the unit of selection?

Strange, yes, but bear with me.  Because if you do this, it opens up a completely new dynamic that must work on evolved creatures, that gives an extremely coherent account of the utter necessity of non-linear change to evolution.

So coherent is this account that it should be very easy to statistically map it.  It should be straightforward to do that, and also to test it.  To test it in simulated computer environments, with rapidly reproducing cell cultures, and to see it very clearly in the fossil record.

If it's not happening, that will be very easily seen.  And moreover - it's not just a case of being able to test whether or not this process exists, but more than this.

It's a case of being able to test whether or not the process accurately predicts the actual contour of evolutionary change as demonstrated by the fossil record.

So what I'm saying is - it's not just testable.  This should, if true, allow a statistician to specifically predict the exact shape of non-linear evolutionary change.  This makes it strikingly falsifiable, with very clear conditions for that, and as such, I believe it should at least be worthy of consideration.

Here's the idea.

People have looked at the benefits a helpful mutation will give to the organism.

But the helpful mutation will also help itself.

It's success feeds back into itself and accelerates the rate at which it is present within an organism, and a population.

The change that mutation brings will therefore amplify.

It will amplify in two ways - in how widespread it is in the population, and how profound a change it makes upon the organism.

As this is a beneficial mutation, the more that change deepens within an organism, the more successful that organism will be, and the more pronounced and rapid that change will become.

This a runaway cycle of change.

The acceleration of the mutation continues until that mutation alone is so successful (not for the organism but for itself) that it starts destabilising the organism.

This puts a huge selection priority for supporting change in the organism.  By this, I simply mean that it is as if the organism is being selectively bred to gain traits that help the main beneficial mutation.

Because of this, if, say, a bat's wings start getting too big for it's heart to pump blood effectively to them, then a specific, and strong selective pressure will be put on that species for stronger hearts.

Also things like lighter bones - support mutations.  The main mutation is creating a powerful, directional, selective pressure.

However - it can't go on forever.  There's only so strong a heart can be before it starts using too much energy, and the bat can't eat enough to sustain it.  There's only so light bones can be before they lack the structural strength to support the organism.

As this occurs, a precisely opposing process to the self-reinforcing feedback will occur.  Self-inhibiting feedback.

What this means is that the survival benefit of the original beneficial mutation starts being counterbalanced by the instability it causing in the organism.

This brings it to a new stability.  And this stability is held together - not by the environment, or habitat outside - but by the internal tension between the positive and negative feedback processes surrounding the central beneficial mutation.

Positive and negative feedback, working to destabilise then restabilise a creature with a beneficial mutation undergoing runaway feedback.

This is a very simple way to account for non-linear evolutionary changes (evolutionary stasis, and evolutionary leaps, and such) within a purely microevolutionary framework.

It also makes clear predictions of the fossil record - that, for instance, evolutionary 'branching' will never occur outside the period of unstable positive feedback - the negative feedback will keep it in check.

Evolutionary branching can only occur in the period where a mutation has destabilised, and will do so because the mutation that is feeding back will spread across local, semi-isolated populations if they are present.  Small changes in the gene pools of each population will mean that the amplifying mutation will play out slightly differently.

Also because the mutation is beneficial, it will probably mean that the organism breaks the previous localised barriers, and comes into direct competition with the other populations who are also undergoing change.

They will compete, and one of only three things will happen.  Either one will overcome the others, or they will all subsume into the same genetic pool - if they are very localised.  If they are not, a new family of very similar species will spring into being at much the same time.

The shape of this process is something I call the 'flat-S' graph.

If you chart this change in a single species, there should be a long line of stasis, then a slowly increasing upward curve of change (as the acceleration takes hold).

This upward curve will straighten out, and become quite a straight upward line, until...

The negative feedback overtakes the process, and the graph curves back to a new stasis.

It looks like the letter 's' that's been pulled at each end to flatten it out a little, hence the name.

This is the prediction this theory makes of all evolutionary change.

Another way of looking at this is that is it a different proposed mechanism for the phenomenon of 'punctuated equilibrium' that Stephen Jay Gould identified in the fossil record, but struggled to account for.  It also describes the core process behind the 'evolutionary leap', and thus could potentially represent a new understanding of the mechanism in evolution that forms the origin of separate, specific, stable species.

It is not purely internal - this process would be unlikely to be triggered by a raw, random genetic mutation.

What would be more probably, I think, would be that a specific kind of shift in environment would strongly emphasise one set of traits over the established balance.

So we wouldn't really be looking at the scratch mutation of a defined trait, more that an environmental shift (of a certain kind) would radically emphasise a very specific, single trait that had, up until that time, been just one aspect of a stable continuum.

A good (if somewhat controversial) way of looking at this might be human beings - that the apes from which we are descended almost certainly had all of our various faculties - intelligence, self-awareness, opposable thumbs, the ability to work with tools (much in the same way that modern Chimpanzees clearly demonstrate all these things).

And when an environmental shift occurred, there was a radical change in the specific profile of evolutionary pressure - a change which centred around a single trait.

With baboons - another arboreal ape that moved to the plains - that trait was physical ferocity.  With gibbons - another arboreal ape that moved to the plains, it was dexterity.  With us, it was intelligence.

I think it credible that the reason it went this way is that the apes from which baboons, gibbons and humans were descended each had one generic, transferable, usable evolved trait that was more pronounced and more directly useful in the new environment, to them, than any other.

It then 'pushed out' all the other traits, destabilised the organism around a specific trait, and mutative feedback took hold.

While it is an extreme thing to say, it is at least potentially credible, that this is the nature of all evolutionary leaps.  And it's interesting to think that evolutionary change, as opposed to evolutionary stasis, usually centres around a single trait that is, in the face of a new environment, used in a way that it has never been used before.

There are other parallels which can be drawn here with certain new ways that the human animal has developed to use the evolved intelligence it has (specifically the scientific method itself) but that's something for another time.

If any biologist or paleontologist, or anyone with any formal training in any related discipline has any interest in working on a paper for this, just get in touch, my door is always open.

If there is a serious problem with this, and you can see it, please don't be shy, post it right up in the comments.

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1 comment:

  1. Cross posted this comment from a different science article, because it's relevant here as well....

    Look - comments on this are for either - paid subscribers only.... or....

    People who have a credentialed scientific background in a relevant discipline. One or the other, or both.

    I make an exception to the paid subscriber rule on the science articles because genuine critique from people with a background in science is something I welcome so much it is genuinely pathetic.

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