Are you a group selectionist?

Many scientifically-minded people believe in the evolutionary concept of group selection, without knowing that the thing they believe in has a name, or that it is, at best, disputed.

Standard disclaimer: Just because I may suggest that something is scientifically true or natural, does not mean that I consider it to be morally good.

So, are you a group selectionist?

  • If you think human morality is easily explained because, as a social species, it benefits the individual to do what’s good for the tribe… you might be a group selectionist.
  • If you think the reason that over 51% of newborn babies are male is to compensate for adult males’ higher mortality… you might be a group selectionist.
  • If you think the reason organisms die is to make room for the next generation… you might be a group selectionist.
  • If you think a widespread gene for homosexuality is plausible… you might be a group selectionist.
  • If you can’t understand why some couples with fertility problems will move heaven and earth to try to have their own biological children, instead of adopting… you might be a group selectionist.

“Group selection” has some different meanings. It can simply mean any kind of natural selection that operates at the level of the group of individuals. Think about several recently-diverged species competing with each other, or several tribes of the same species competing.

But what it really means is the proposition that group-level selection is a major driving force of evolution. The idea is that individuals who sacrifice some of their personal well-being to do what’s good for their group will be rewarded, and ultimately be more successful at propagating their genes. Or, dropping down a level, that a gene that causes its body to do what’s good for the group will be more successful at propagating itself.

There are some professional biologists who give group selection a lot of credence. Who am I to say they’re wrong? But if they can make a good case for their position, I haven’t seen their evidence. The critics of group selection make a much better case, in my humble opinion.

The case against group selection was first brought to public attention by Richard Dawkins, in his classic 1976 book The Selfish Gene. It might be a little dated, but it still does the job well. I recommend that you read at least a chapter or two of it, or some other criticism of group selection, before assuming you have a good understanding of the driving forces behind evolution and natural selection.

The crux of the issue is that there is seemingly no significant force that would select against a gene that, while being good for the gene and the individual, is bad for the group.

Genes are not conscious entities, but sometimes it can help to think of them as such. Genes behave as if their want to be in 100% of the bodies in their group. Genes don’t care how well their group competes with other groups. Genes don’t care about the number of members of their group. Genes don’t care about their group’s biomass. Genes don’t care about the distant future. For a gene, to “win” is to be present in virtually 100% of the bodies that make up its group.

Example 1

Imagine a tribe in which individuals regularly sacrifice some of their own well-being to do what’s good for the tribe. Other members of the tribe reward those individuals in some way. In turn, tribe members who give out these rewards are treated well by other tribe members. And so on.

Such a tribe would out-compete rival tribes. But it’s probably not in a stable state. What’s being selected for is not actually doing what’s good for the tribe; it’s appearing to do what’s good for the tribe. The very best thing to do is to cheat somehow, and get rewarded without making a sacrifice. And instead of rewarding those who sacrifice (or appear to sacrifice), the other tribe members should also cheat, and only appear to be handing out rewards.

Gene games like this are being played in all the tribes. In the long run, it’s unlikely that genes for sacrificing yourself will continue to be successful in any tribe. It doesn’t matter that such a tribe would be successful.

Example 2

Consider the question of why organisms die. Or at least, why so many of their lifespans seem to be unnecessarily short. The group selectionist might explain that organisms die to make room for the next generation of their species, or to avoid competing with their own children.

The gene-centric selectionist would find this claim dubious. There’s just no reason to care about unrelated members of your species. Competing with your own offspring could indeed be bad, but if nothing else, why not simply walk or fly far away from your offspring? You might end up in a less hospitable environment, but even if your chance of ever reproducing again is slim, slim is better than the zero chance you would have if you simply died.

The real reasons organisms have the lifespans they do can be complex. All other things being equal, longer life is almost always better for your genes. But all other things are rarely equal, and what really matters is how many successful offspring you produce in your lifetime, not how long you live.

One could argue that this is shortsighted. Couldn’t there also be a higher-level selection force, which favors groups that have some sort of resistance to such bad-for-the-group genes? I would agree that such an effect exists, and in a few cases it might be quite significant (I’ll cover one of them next). But in general, this meta-selection is so weak and slow that it is completely lost in the noise of the normal kinds of gene selection.

The exception that proves the rule?

The gene-centric selectionists have an embarrassing problem: sexual reproduction. Gene selection seems to predict that asexual reproduction will win out over sexual reproduction. With asexual reproduction, your offsprings’ genes will be 100% yours, which is far better than the 50% offered by sexual reproduction.

It’s easy to think of reason why sex might be good for the species. Diversity, and all that. But (1) when you do the math, the pros don’t seem to outweigh the cons, and (2) as per the entire thesis of this post, evolution doesn’t usually care about what’s good for the species.

This is especially frustrating because a lot of the dubious claims made by group selectionists involve sexual reproduction in some way. Rebutting such a claim is complicated, because you have to start by making a long detour full of excuses for the very existence of sexual reproduction.

Maybe sex is just the exception to the rule. Maybe the group selectionists are right this time. A sexual species that reverts to asexuality may do very well for a while. But most likely, before very long, a specialized parasite will do it in. The world will be left to the sexual species, inefficient though they may be. I won’t attempt to tackle the obvious followup question of how sexual species achieved their dominance in the first place.

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