Saturday, February 18, 2012

Exam Question #2

 
Most of you wouldn't have passed Exam Question #1. Let's see how you do with this one.
Here’s a quotation from an article published by Kathleen McAuliffe in Discover magazine in 2009 [They Don't Make Homo Sapiens Like They Used To].
For decades the consensus view—among the public as well as the world’s preeminent biologists—has been that human evolution is over. Since modern Homo sapiens emerged 50,000 years ago, “natural selection has almost become irrelevant” to us, the influential Harvard paleontologist Stephen Jay Gould proclaimed. “There have been no biological changes. Everything we’ve called culture and civilization we’ve built with the same body and brain.” This view has become so entrenched that it is practically doctrine.
Is it true that the consensus view among “the world’s preeminent biologists” is that human evolution has stopped? Do you agree with this “doctrine?”


26 comments :

  1. I am merely an interested amateur, but I wouldn't see how this could be true. Our environment has changed dramatically in the last several thousand years, the natural and human-made urban environment, no doubt mutations in our genome continue, so it is not sensible to think that the evolution of H Sapiens is over ... which is a good thing, we perhaps need some improvement overall

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    1. I see I forgot to answer the first part of the question. While I doubt that a consensus view of "the world's preeminent biologists" has ever been the human evolution has stopped, I also doubt that any poll of an agreed, defined group of "the world's preeminent biologists" has ever been taken on the subject. This is the sort of sweeping claim unsupported by evidence, that is made by those peddling something suspect, like Deepak Chopra (I mention him because he was on CNN for too long today).

      But, Gould may have been right in the practical sense; 50,000 years or about 2500 generations for humans is not that much for vast evolutionary changes so we certainly are evolving, but it may also be true that our bodies and brains are not much changed over that time.

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  2. I enjoyed the comments and the reasoning behind the last exam question, I patiently await the discussion that this one creates. :)

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  3. Well, I don't know what a "preeminent" biologist is, nor do I care. Authority is not what determines scientific validity; evidence is. I would say that of course human evolution has not stopped. Such a statement is silly. The paragraph quoted implies that evolution consists only of anatomical features modified by natural selection. This is demonstrably false. Most of our evolution has been and continues to be in neutral parts of the genome as evidenced by the variation uncovered by the human genome project.

    As populations of humans intermingle on a global scale, I would predict that allele frequencies within populations (or subpopulations) will continue to change with some alleles (including those that code for visible traits) increasing in frequency and others vanishing from existence. Some of this might be due to selection (N.S. & S.S.) but a lot of it will probably be due to the vagaries of chance. What will determine the success of that prediction will be evidence, not authority.

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  4. So you teach a course on evolution? I thought it was biochemistry.

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    1. The course is called "Molecular Evolution." I spend a lot of time on defining evolution and explaining random genetic drift and neutral alleles. These are essential concepts in molecular evolution. Although this is a fourth year course, these concepts are quite new to most of the students.

      They have read articles and listened to a podcast on the issue of whether humans are evolving so they should be well aware of the controversy and, hopefully, will have an opinion that they can defend. All they have to do is proposes a reasonable definition of evolution and then describe whether the human population is evolving or not, according to their definition of evolution.

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  5. Well, at least among the biologists I know, it is not true that evolution in humans has stopped. If we go by the definition: "changes in allelic frequencies in a population," there's no way of stopping this. We have added to the changes in allelic frequencies too. Example, penicillin saved my life when I was a very little kid. Now I have children of my own who add to the changes in allelic frequencies in the population.
    I think the idea of "stopped human evolution" stems from the perception of evolution as an upward spiral.

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  6. Oh, almost forgot. I think that the discover magazine was being both ignorant and stupid by thinking that natural selection is all there is about evolution.

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  7. Would an answer like "No. No." be graded as 100%?

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    1. No. This is university, not kindergarten, or law school. They would get no marks at all on this question.

      Any student who just writes, "No, No" is clearly not mature enough, or smart enough, to graduate from university. In university level classes it's a given that you have to justify and defend your answer except on multiple choice exams.

      I used to write "explain your answer," or something similar, on all my exam questions but then I realized that this was silly. I shouldn't have to explain to adults in a university class that this is something we expect in all answers. I was being part of the problem by treating them like kindergarten students who needed explicit instructions on how to write answers on a university exam.

      Unfortunately, there's a complication. Other courses will often accept answers that don't explain the reasoning. This makes it difficult to enforce a different standard in my courses. Even worse, the university would probably overturn my grade if the student appealed my decision. The university appeals committee would probably insist that I should have written "Explain your answer" because university students don't realize that they should do this without being asked. (I served for three years on the university appeals committee.)

      BTW, if I have to give full marks to "No. No." is there any combination of "yes" and "no" that would not deserve full marks?

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    2. I was just curious precisely because I found a lack of "explain your answer" a little odd. Not an issue if students know what you require.

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  8. It's a question that is easy to answer

    But there’s something I don’t understand here. The quote from Stephen Jay Gould is strictly false, but I think it was more of a blunder than anthing else, and the purport of this blunder have been exaggerated. Having said that SJ. Gould was certainly wrong in some of his remarks in paleoanthropology. But his present quote was never (to my knowledge) a consensus!

    Oh and if I have some problems with SJ. Gould because of his ideological bias and some dubious claims at least SJ Goud admitted his ideological bias. On the other side I have equally, if no more, feelings about some of Henry Harpending’s claims like this one among many more about people of african descent, poor people etc... I think it would be nice if Henry Harpending also admits his ideological bias.

    Fortunately there’s an excellent website about anthropology and I strongly recommend this article.

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  9. What are your criteria for deciding that the answer to "do you agree with this doctrine" gets full marks, assuming the answer is logically consistent and contains no factual errors?

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    1. My criteria are logical consistency and absence of factual, and conceptual, errors. What did you expect?

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    2. That seems fair enough - about what I expected, but I was ready to be surprised.

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    3. Do you deduct marks for spelling, grammar, and punctuation errors?

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    4. Given that you don't accept "no" as a sufficient answer, those are clearly not your only criteria. Very often the difficulty for students is that it is not clear how much they should write - presumably you don't expect a multi-page essay, but you clearly have some (unstated) minimum length or content requirement.

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  10. I've not really read into this (my course has only dedicated 2 lectures in 2 years to evolution to date), but I imagine that forces like sexual selection operate to some degree, lessened by influence of culture. There would probably be a large amount of neutral changes, such as silent mutations, and less phenotypic changes.

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  11. Even though selection is not as drastic as it was when resources were scarce and the environment humans lived in was far more unpredictable, this does not mean evolution has stopped.

    - Random genetic drift occurs independently from any selective forces. This means that the DNA of a population will change over time, even if most change seems like "noise".

    - Selection forces have changed but they have not gone away.
    -- Any propensities towards reducing the reproductive fitness will be selected against (such as predisposition towards competing in the Darwin Awards or playing World of Warcraft =)).
    -- Any propensities towards increasing the reproductive fitness will be selected for (such as believing in "abstinence-only contraception" - see the teen pregnancy rates in certain US states which clearly disfavors responsible teens who use contraception).

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  12. I can't really address the preeminent part, there's really no criteria for that qualification. On the other hand, being reasonable, I suppose we could at least include Gould and Dawkin's on that list. I suspect Dawkin's ideas would, perhaps surprisingly given that we normally think of them as being at odds, in some ways match Gould's; physically there don't appear to be very large changes between a randomly selected person from today and from, say, the Pleistocene. So I think Dawkin's wouldn't see much adaptive changes, and (being a hyper adaptationist) he might agree there hasn't been much evolution.

    The other problem with this assessment of course is that evolution doesn't only include adaptive changes, and clearly there have been 'changes in allele frequencies' in the human population since the Pleistocene.

    Another issue that there's some contention over is that there may infact have been some pretty big changes, of the sort we traditionally associate with 'adaptive evolution' since prehistoric times, like changes in the structure of our brain or the soft parts of our 'voice box' that allow for speech and perhaps complex culture.

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  13. I may be misremembering, but I recall that both (A) widespread tolerance for (relatively) high levels of alcohol and (B) widespread adult lactose tolerance are phenomena which appeared within the last 50000 years, and both are genetic AND a result of the environmental pressures of civilization. (Adult lactose tolerance in particular -- again IIRC -- is linked to dairy-herding cultures. If your ancestors didn't make cheese, you probably will become lactose intolerant as you get older.)

    Assuming this is correct, then regardless of the answer to the first question, the second one is necessarily "no". I suspect that "the world's preeminent biologists" do not agree with the idea either, since they would have to be ignoring a direct counterexample. But their agreement or disagreement is largely irrelevant, because this is a question of evidence, not one of appeal to authority.

    How's that as an answer (keeping in mind that I am a random stranger from the Internet, rather than someone who has done your specific course reading)?

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  14. McAuliffe is quote mining. Here is the full interview with Gould, the quoted part is on last page in the third to last paragraph:
    http://goo.gl/XxKbZ

    As can be seen Gould is contrasting the speed of cultural change with evolutionary change in humans. The difference is on the scale of orders of magnitude. His statement is similar to saying a snail had not moved forward in the time a car drives down a road. Even if Gould had added qualifiers such as "virtually no change", or "no significant change" it wouldn't have stopped this quote mining.

    Also while opinions take a backseat to facts in science, biologists should have precisely this mindset. So if "preeminent biologists" assert the truth of a certain statement, that is a strong indication that the statement has been proven by experiment, or in the very least is very plausible. Most importantly dismissing their assertions as "mere opinion" would constitute self-deception if done before verifying the sources of their opinion.

    However there is no indication that biologists have embraced the non-sensical view that evolution has stopped for humans. Quite to the opposite the notion is commonly dismissed by biologists, e.g. here:
    http://goo.gl/s9ZiB

    Finally evolution is heritable change in populations over time. It is happening all the time, for example the Cro-Magnon had about 14% larger brains than we do now. As a much more recent example the black death in 14th century Europe had a measurable impact on allele frequency.

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  15. It seems to me evolutions stops only when DNA polymerase ceases to incorporate mutations in heritable DNA (just to pretend for the moment that this is the only means of genetic change). Since the incorporation of mutation by DNA polymerase is inevitable, then evolution is inevitable. Change in observable morphological characteristics (notwithstanding the fact that this process stills occurs in humans) is not an essential element of evolution. Or alternatively, one could say that a change in the DNA sequence (any nucleotide, anywhere) is itself a heritable morphological change, just one that is not in itself macroscopically observable. (I realize this totally ignores things like fixation of alleles etc, but is my highly reductionist (I dislike that term by the way)concept of evolution misguided? This isnt a rhetorical question by the way...would appreciate feedback if any one cares since I am no expert in evolutionary theory.

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  16. No and no, but humans do have a pretty small effective population size, and thus Ne*S...

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  17. human evolution is over. Since modern Homo sapiens emerged 50,000 years ago, “natural selection has almost become irrelevant” to us

    “There have been no biological changes. Everything we’ve called culture and civilization we’ve built with the same body and brain.”

    Natural selection becoming nearly irrelevant doesn't mean evolution is done and over with. (Though I'm not sure "nearly irrelevant" is the best phrase to use outside the specific context Gould waS speaking in, i.e., body and brain changes dramatic enough to substantially change the way we, or whatever one wanted to call the new subspecies, think and act. Sickle cell trait, for example, shows malaria hasn't been "nearly irrelevant.")

    The Discover article makes the usual Great Mistake of equating natural selection and evolution. Though a great deal of obvious selection of substantially new morphologies hasn't occurred (cf. skin color?), mutation and drift are humming right along.

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