Not for the sake of the species

I frequently come across statements implying that a particular trait evolved because it increases the fitness of the species or that a behavior observed in some animal exists because it helps the species. I hear this from not only members of the general public, but also from biology students and even biologists whose work does not directly address evolutionary questions. Please be aware that this is almost entirely wrong.

In most circumstances, natural selection favors traits that increase the fitness of those individuals that have those traits. If a heritable traits is good for the species but bad for the fitness of those organisms that have it, then those that have it will tend to survive or reproduce less well than those that don't, such that in subsequent generations, the trait will be repeatedly rarer in the population. Even if it is good for the species but has no effect on the fitness of the individual, there is no strong reason to expect that it will increase in frequency.

In some special situations, selection can favor a trait that increases the frequency of a gene in the population, even if that gene causes the individuals that carry it to live less long or reproduce less well than individuals that don't have it. And there are indeed some cases where some biologists reasonably argue that selection occurs at the group level, with traits of the population or group determining which groups survive and which die out. But in almost any popular science context, if you imply that something is for the good of the species, you have gotten it wrong.

Note: this is something I started writing about a year ago, and never finished, until now. I had some particular example in mind, but don't know what it was.

Decleration of intent to start blogging again, I hope.

In some weird way things have settled down enough that I can consider blogging (briefly) again. I do miss it. So much to say, so little time. Much of my blogging will likely be done late in the evening while holding my tiny baby and listening to my sleeping girls. But I'll try.

Let's start with this: I don't have to move my family anywhere in the near future. We are in Madison, Wisconsin, and I have a great job here: Associate Scientist in the Department of Botany at UW-Madison. Being a scientist who doesn't have to currently think about moving to another country or continent is kind of lovely.

Okay, more soon, I hope, about science, I hope.