Are animals optimally adapted to their environment?

I have always had a strong distaste for the idea that animals are optimally adapted. Luckily, it doesn't seem to be a widely accepted concept, because if everything was optimally adapted to their surroundings, then everything living in the same environment should look exactly the same.

I might have just misinterpreted the concept, though, because I hope you agree with me that the idea sounds rather absurd otherwise...

Still, optimisation has been used quite a lot, in particular in paleontology. It is mainly used as a practical assumption to provide a framework for objective models, for example when studying how e.g. Tyrannosaurus rex moved. What I mean by that is that scientists use knowledge of physics and biomechanics, combined with measurements from the fossils, and put it in a big computer, which works out - by trial and error, I guess - the optimal movement style.

Therefore, one should take the results of such studies with a pinch of salt: they are not aiming to reflect the most likely reality, but aim to work out the best way to move. Or, if they were aiming to represent the most likely scenario, they probably missed the point. The optimisation assumption is accepted because it is a simple way of setting up a goal or framework for the mathematics to work toward.

It is exactly the same with the parsimony principle in phylogenetic trees of life we see everywhere today. The principle of parsimony, also known as Ockham's razor, states that the simplest explanation is the most useful to humanity. The word 'useful' is more important than I can emphasise. The simple theory is not more true, just more useful.

Now, part of the beauty of nature, which I'm sure most scientist would gladly advocate, is that nature is hugely complex. If you consider nature to be un-simple, and simultaneously accept assumptions that treat is as simple, you are being inconsistent.

Thus, when the evolutionary biologists are creating their phylogenetic trees of life, they are not working out the one that is most likely to be true, but the one that is the most simple, i.e. that can explain all the data with least twists and turns.

The only reason we accept these assumptions is that it allows us to work things out objectively and with common standards, if we all just agree to assume that the optimal model, or simplest solution, are the most likely to be true. We accept it because it is practical.

But the scientist leave that part out.

Today, in a lecture on evolutionary biology, we were told about an example where two traits that are genetically linked, i.e. always inherited together, make it impossible to reach an optimal solution, because that optimal state is having only one of those traits. The particular example is the strong positive relationship between beak depth and beak length in finches, and maybe other birds too. A deep – i.e. thick – beak is capable of delivering stronger force, and a shorter beak means that the force is distributed over a smaller area; thus, the optimal design would be deep and short, but you never get that because both traits are linked, so you either get a shallow and short or deep and long beak.

This is clear evidence that the optimisation assumption is flat out false. But we still accept it, because it is practical.