Thursday, September 12, 2013

Humans Are Still Evolving

Sir David Attenborough said something stupid the other day [Sir David Attenborough: Humans have stopped evolving]. (Not for the first time.) He said ...
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.
The headline says that humans have stopped evolving. If that's what he really said then it's easy to prove him wrong by showing that there's a lot more to evolution than natural selection [Have Humans Stopped Evolving?].

But what about his specific claim that natural selection doesn't work on humans any more? I covered that in earlier posts but John Hawks has corrected him today [Humans are still evolving, and soon we'll know a lot more about it]. I love it when I agree with John Hawks! (That's me, visiting him in his lab in Madison, Wisconsin.)


26 comments :

  1. How can humans still be evolving if their genome is actually deteriorating as a result of accumulating of thousands of deleterious mutations?

    As a matter fact, human mutation rate is too high for man to have evolved from anything and if that is proven it would show that man in fact is regressing.

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    1. How can humans still be evolving if their genome is actually deteriorating as a result of accumulating of thousands of deleterious mutations?
      Most of those mutations are only slightly deleterious, not lethal, and they are often counterbalanced by a few rare but strong beneficial mutations. It is a creationist myth that the genome is "detoriating". When enough deleterious mutations have accumulated, the carrier simply dies. This leaves primarily the healthy offspring to survive and reproduce. See how that works? Having lots of offspring ensures there's still a large and healthy genepool, among other things. As usual, your creationist thinking is too simplistic. There's more to evolution than mere accumulation of slightly deleterious mutations. It's a population level phenomenon, and the number of offspring is important too.

      As a matter fact, human mutation rate is too high for man to have evolved from anything
      That is not a fact, that is a creationist lie. Care to show your math?

      and if that is proven it would show that man in fact is regressing.
      Yeah, but it isn't proven, it's actually demonstrably false. Ever heard of neutral theory? Biology is more complicated than your black-and-white, absolutist creationist thinking. There is more happening in our genomes than just "accumulation of thousands of deleterious mutations".

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    2. As a matter fact, human mutation rate is too high for man to have evolved from anything and if that is proven it would show that man in fact is regressing.

      Yes, please show your work. What is the specific threshhold that you use to measure whether something is designed or a product of natural processes? What baseline do you have and how was it established?

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  2. I think there may some semantic confusion between "evolving" and "improving". Many of us, including me, think of evolution as becoming more fit (adapted better to the environment). This is what happens when evolution is driven by a selection criterion, as in the case of natural selection, but as our host tirelessly points out, this is not the only way in which population genetics can change over time.

    Speaking of negative mutations, I probably have one myself. None of my parents, siblings, grandparents, or first cousins were/are near-sighted, but I am. Without eyeglasses I would not be worth much to society, and I probably would not have survived in a hunter-gatherer era. Of course, the majority of significant negative mutations probably prevent conception or cause miscarriages.

    Many science-fiction novels speculate that humans will develop the technology to correct and enhance DNA - not through eugenics but by direct modification of genes.

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    1. Nearsightedness can also be caused by lots of reading at an early age. There was talk a while back about prescribing glasses for young readers to protect their vision, but I have no idea what became of that plan.

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    2. @John Vreeland - thanks for the interesting information. I did lots of reading (Dr. Seuss books, cereal boxes) before I was old enough to go to school - and then could not read the blackboard from the first row of seats. On the other hand, I am not sure the studies support such a strong early effect.

      So far, after brief googling, it seems the jury is still out:

      "... and some studies suggest that near work may exacerbate a genetic predisposition to develop myopia. [55] Other studies have shown that near work (reading, computer games) may not be associated with myopic progression, however. [56]

      55. Wolffsohn JS, Gilmartin B, Li RW, et al. (May 2003). "Nearwork-induced transient myopia in preadolescent Hong Kong Chinese". Invest. Ophthalmol. Vis. Sci. 44 (5): 2284–9. doi:10.1167/iovs.02-0373. PMID 12714672.

      56. a b Saw SM, Tong L, Chua WH, Chia KS, Koh D, Tan DT, Katz J (January 2005). "Incidence and progression of myopia in Singaporean school children". Invest. Ophthalmol. Vis. Sci. 46 (1): 51–7. doi:10.1167/iovs.04-0565. PMID 15623754."

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  3. He made a boo-boo, but it doesn't change my high opinion of him or his work. He has set the standard for nature documentaries, and I don't know of anyone who comes close.

    Dave Bailey

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  4. I loved his series on birds. It was excellent.
    Man never evolved in the first place. This is a hypothesis with no supporting evidence to raise it to a theory. People just want it to be true.
    If man could evolve more today, then it would have to cross reproducing segregated groups called mankind.
    How would that work?
    Man has changed from innate mechanisms in the body as shown by the colours and other details in mankind BUT its not been from mutations being selected plus time.
    There are no intermediates in mankind . No one on their way to a new look!!
    Everyone is stuck in gear.

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  5. Humans have not stopped evolving. But when I am asked about that, I try to emphasize that any changes in the human body or brain will be very slow, very small, and very trivial compared to changes caused by social (cultural) evolution. If, 100 years from now, we are all much healthier, social evolution will be why, not biological evolution.

    This is important to emphasize because people tend to focus on biological evolution. In this context, Attenborough's error is a small one. Should I also talk of Moran's omission, a larger one?

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    1. Should I also talk of Moran's omission, a larger one?

      Yes, please.

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    2. why should changes be slow ? PE said or came close to saying changes can be fast and important and so why not recorded in the fossil record!
      Why should there be changes in the brain if we are segregated populations!
      Are we now equal in brain size/smarts??
      No one a ''small" bit higher or lower?
      As a YEC we say there is no difference in human intelligence and in fact the brain is unrelated to human intelligence. We are souls only. The brain is a mere middleman.
      The brain is not evolving.
      Anyways if selection needs to bring/confirm changfe , by mutations I presume, then HOW do segregated populations get the same juice?
      Maybe I'm more evolved then those on the other side of the planet?

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  6. He made the common, albeit painfully persistent mistake of equating evolution with natural selection. I think it is a forgivable error from someone who is not a research scientist, but devoted his whole life to bringing nature into hiw viewers' home and explaining natural processes with his documentaries. As a science teacher I always enliven my classes as often as possible with clips from his films. At the end of my students' 3-5 year biology curriculum they have watched a few parts from most of his major series. Having said that, there is a message in this for all the great popularizers of science: they should listen to and if in doubt shouldn't hesitate to turn to active researchers for clarification in their field.

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  7. Neutral evolution aside, it's true that selection on a number of features has relaxed, as tends to be the case in any rapidly expanding population. There's still selection on other features, though.

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    1. Assuming the desire to have and raise children is at least partly a heritable trait, the ready availability of birth control may tend to lead to an increase in this trait (rather than merely sexual desire leading to procreation).

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  8. In theory, evolution emerges through survival and for survival. Humans are still genetically adapting in the face of the survival of the fittest, and yet on the grand scale of evolution, we are becoming what we have always been - human.

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    1. If god has breath, can she have bad breath ?

      Do you think that telling outright lies, like Planned Parenthood urges abortions for pregnancies during difficult life situations makes you more human ?

      If the law of the old testament has been superseded by the law of christ then why did Jesus say Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil. ?

      Do you just ignore the parts of the bible that contradict each other ?

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    2. @dogsbreath:

      Was this chap human, or was he not? http://en.wikipedia.org/wiki/File:Homo_erectus_new.JPG
      (If not, then what)

      @Steve: regrettably, he's probably a drive-by

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  9. You are under no logical obligation to add this, but I think it is important to remind people that social and cultural change will have a much bigger impact on our lives, for good or for bad, than biological change. When people get excited about whether our brains will get larger or our wisdom teeth smaller, they are talking about changes that would be on a very long time scale.

    I think that they forget that cultural / social / economic / political changes on that time scale will have a vastly larger impact, to the point where one can more or less ignore the change due to biological evolution. And that failing to remind your audience of that is unfortunate.

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    1. Sorry but when I talk about evolution I'm usually not thinking of humans. And when I do talk about human evolution I'm only thinking of biological evolution.

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  10. (That above is a reply to Larry's "please do" comment above, but of course I pushed the wrong button ... )

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  11. Why not? Your science is out of date and even Larry forgot you had spent half of your life trying to prove your shit, that Harshan thinks is shit...JFelostin... You are ....

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    1. I don't know who "Harshan" is but you don't know anything about me or my work. Starting with the correct spelling of my last name ...

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    2. JFelostin: I suspect I'm Harshan. I can't explain what might belong in the ellipses.

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    3. Hashan: You stand exposed as an ignoramus who can't even fill in ellipses! You have failed and will never be a troll. JFelostin.

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    4. ... just as I will never learn to spell "Harshan".

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    5. JFestln: Not your ellipses. Quest's ellipses.

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