Change

I've been reading Stephen Jay Gould. This man has the power to cheer me up, make me think, make me laugh, make me interested in baseball (and Hershey Bars) and, above all, he has the power to make me understand things better. I haven't read any of his purely scientific writing (he was a palaeontologist and an evolutionary biologist, a geologist and philosopher by training) but I've made an effort to collect his books of essays (I say I've made an effort because I look for them in every secondhand bookstore, painstakingly, just to make sure these wonderful places where I can spend hours on end survive the coming of the digital secondhand store), which have made me fall in love with popular science writing more than any other work.

Stephen Jay Gould had a lot to say about about evolution and adaptation, but more than anything, he had a lot to say about how we view these two processes and how we study them. He was the one to say that evolution is both a theory and a fact (possibly the only instance in science where this is true), and he regarded evolution as a "historical science". By this, he means that evolution is a process that takes place in time (this may seem obvious), and that as such it hasn't finished (this may seem less obvious) and it's not static (this last one may seem like the most obvious, but it's really not).

Today I feel like talking about evolution and adaptation, and for that I first need a few simple definitions.

Evolution: process of change in living organisms mediated by hereditary mutations.

Natural selection: the mechanism of evolution. The death before reproduction of those organisms with mutations that are prejudicial and the survival of those with mutations that don't affect them or that are beneficial. The better survival of organisms with mutations that are beneficial to them, and the fact that because they survive better they are better capable of reproducing and carrying on these traits into the next generation.

Adaptation: a by-product of natural selection, the favourable selection of traits that allow better survival in an environment leading to organisms developing structures that are useful in the environment they've evolved.

Being a biology (OK, biochemistry) student myself, I sometimes find myself thinking of things causally: "the eye evolved so organisms could see". This is a fallacy of course, but it becomes even more of a fallacy when used to try to explain every single trait as an adaptation. Contrary to popular belief, complex organisms aren't adapted to their environment, because their adaptation to their current environment is heavily limited by millions of year of evolution. If most of their evolution occurred in a different environment than the one they occupy today, then they won't be adapted. They may have some mode of adaptation, but most of their characteristics will be a product of earlier adaptations, of the path they had to take to get to where they are now, and all the circumstances that surrounded that evolution.

It is important now, that we are well into the era of molecular biology and genetics, that we are understanding the biochemical mechanisms of evolution better, not to forget this. That evolution has been occurring for over 3700 million years. That what may have been useful three million years ago may not be as useful now, but that three million years is too short a time to change something that evolved in 2997 million years. That evolution is still happening, that we (as human beings) are not an optimum, and that no other species is either (with the exception, perhaps, of some insects, my favourite being ants, that haven't changed much for several million years, a fact that is often used in arguments against the theory of evolution), that adaptation is a beautiful example (and proof) of evolution, but that not all organisms are adapted (not to mention "well" adapted).

Most biologists working nowadays accept that mutations are random, that evolution doesn't have a direction. Let's not forget that although this may be true, it is important to acknowledge that evolution is also constrained, that not all changes are possible for all organisms, that some paths have not been tread, and that other paths have been tread unsuccessfully (ask Ediacarans).