Humans are still evolving (Sir David Attenborough is wrong on this one).

The Guardian today published a report on Sir David Attenborough intervention at this week’s Radio Times.

Apparently he said the following:

I think that we’ve stopped evolving. Because if natural selection, as proposed by Darwin, is the main mechanism of evolution – there may be other things, but it does look as though that’s the case – then we’ve stopped natural selection.
We stopped natural selection as soon as we started being able to rear 95–99 per cent of our babies that are born. We are the only species to have put a halt to natural selection, of its own free will, as it were.

Now, I idolize the man, but the point he’s making is just wrong. I’ve also had a brief Twitter conversation on this, and promised to do some homework, so here is the result.

First, why is Attenborough wrong? In short, because you can’t stop natural selection, you can only divert it. Natural selection will always be active, and if the main selective forces may disappear for any given reason, other selective forces simply become more relevant. Sir David is right in pointing out that the moment we became able to “rear 95–99 per cent of our babies” we changed things dramatically. With civilisation, we decreased the selective pressures that favoured people able to stay away from dangerous predators, hunt effectively and so on. With the recent advances of medicine, we also stopped (most) selection on our ability to survive or escape deadly infections. That’s true. However, if a genetically inheritable trait gives a higher probability to produce a larger-than-average offspring, this would still increase its frequency over the generations. The reason is already in my definition above so I don’t think it needs an explanation; in fact, it is so inevitable that it doesn’t even need to be empirically demonstrated (admitting that this would be possible, when dealing with humans).

I will substantiate this claim with two examples (also because I mentioned one on Twitter):

Example 1, taken from The Journal, quoting Dr Ian Rickard  (evolutionary anthropologist at Durham University):

Consider gene variant A that predisposed someone to put on fat more than the alternative variant B.
Before the widespread availability of high energy foods in Europe, gene variant A might be more common than B because it helped people retain their energy balance under conditions of food shortage, allowing them to survive and eventually reproduce.
However, nowadays A would be more likely to lead to obesity and diabetes and premature death, perhaps before the person with the gene had children.
Having the B variant would not be so disadvantageous when there’s lots of high-energy food available.
This means that B would be now be relatively more advantageous than A. As a result, natural selection against A would decrease, and selection for B would increase. If the selection pressure were consistent over time, this would cause B to become more common, and A to become less common

Seems an obvious and inevitable prediction, given what we know about inheritance. You don’t even need to accept the full theory of evolution, you just need to accept that inheritable traits may or may not predispose people to put on fat.

Example 2 (my own) can be seen as a variation of the first one.
Say that you have an inheritable trait that makes you less rebellious during the adolescence. If you have this trait, and happen to be raised in a strict Catholic family that fully embraces the Church opposition on birth control, you’ll have more chances of retaining this belief, and will consequently have higher chances of producing many children. These will have a higher than average chance of being less rebellious, and will therefore reinforce the trend. The selective pressure here is created by the different attitudes of different cultural groups, so this example is also a neat explanation of the basic idea behind what can be described as genetic and cultural co-evolution (the ideas will tend to spread along with the genes).

One may think that the question becomes: does such a trait exist? Well, it’s irrelevant, because traits that favour different degrees of retention of learned beliefs certainly exist, and if they don’t, they will be favoured as and when they will emerge. As it happens, in the current (Western) world, when a “stick to your family’s beliefs” trait  appears in a cultural group that encourages large families (doesn’t need to be a religion, but in the world I know they usually are), such a trait will spread over the generations, and because it will be associated with a particular culture, the culture itself will be favoured as well. This is not an opinion, it is again the direct consequence of verifiable evidence. This is why I’ve tweeted “You can’t stop nat-sel. It’s still active, promoting new things, such as religiosity, as it favours large families”.

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Posted in Evolution, Evolutionary Psychology, Religion
5 comments on “Humans are still evolving (Sir David Attenborough is wrong on this one).
  1. Akshat Rathi says:

    Thanks for taking the time to write this. Sadly, point 2 is moot. Say there is a religiosity trait and taking your example of Catholics, say, more of babies with that trait are created. Human population is large enough, culturally diverse enough and our existential risks great enough that to it the effect on either population or culture will be hardly seen as a direct result of evolving this trait on human civilisation. Which is to say that your hypothesis may be theoretically falsifiable but not practically not so.

    • Sergio Graziosi says:

      Hi Akshat,
      thanks for replying, I am acutely aware that I need my views to be intelligently challenged.

      I’m guessing we are talking at different levels here. I’ll clarify what I am not saying, just to make sure there is no misunderstanding.
      1) I am not saying that evolution creates good results. So I’m not trying to suggest that the the fact that natural selection still operates on human populations is good per-se, and neither that the possible effects on gene-culture co-evolution are good. (Quite the opposite, in fact)
      2) I am not saying that we can see, measure, and/or that we should quantify the results of my second example. In fact I’m saying that we can safely assume that the effects are there. Whether it is feasible and/or interesting to try to put numbers on it was completely outside the scope of my quick reaction. (This should address your “moot” point, as in “of little or no practical value or meaning; purely academic”: yes, my point was purely academic, it doesn’t need new or specific empirical evidence to be made)
      3) I am not saying that given enough generations (in the current conditions) all humans will be religious, or Catholic. The fact that there is one selective force that favours some traits doesn’t mean that there aren’t counter-balancing forces. Also, I’ve said/suggested nothing about how far we are from reaching the steady state where the opposing forces create a more or less stable equilibrium. (This should address your point on population diversity)

      Keeping 1-3 in mind, I will re-state my main point.
      Natural selection still acts on human populations, even the safe and cosy Western ones, and I’m sorry to hear that Sir David Attenborough thinks it isn’t. Somebody (CaressOfSteel) at the Guardian commented “I suspect that this is a case of misrepresentation or misunderstanding by a journalist and is not a direct quote”, and believe me, I hope that’s the case!
      Essentially, I suspect you were expecting me to have a different point to make, sorry to disappoint!

  2. Akshat Rathi says:

    Thanks for that and apologies for the many typos in my previous comment, I think I was bit dazed when I wrote that. Anyway, yes the points about Attenborough were well taken. I think he’s got a few things wrong. You’ll see more articles on that on The Conversation soon.

    And yes may be your point is of academic interest, but then if it’s not practically falsifiable it’ll remain as a thought experiment. Nothing wrong in that.

  3. […] This suited me quite well: as my readers will know, I indulge in philosophy quite a bit. That’s because I’m lazy: thinking is cheap, it comes much easier to me than trying to do anything at all. Hence, the definition above avoids to add something that specifies that much of philosophy speculates on subjects that are (or are supposed to be) difficult/impossible to investigate empirically. I my case, I’ll be naturally inclined to think as much as I can, and verify later, only if/when I really need to. I’ve exemplified this attitude in one of my one-off posts, to refute the idea that human evolution has stopped. […]

  4. […] *It’s even more interesting to note that frequently, when I write an angry reaction, the resulting posts also happen to be among the most popular on this blog, see for example here (with follow-up) and here. […]

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