In a recent podcast, Dr. James Tour had this to say about the state of evolutionary biology at the 33:02 mark (thanks to @Rumraket for providing this):
“I’ve been told by geneticists that, that they no longer are pushing random mutation and natural selection, they’re pushing ahh neutral drift, the changes that occur from a parent to their children and then on to their children, and the theory of universal common descent. So it, that, that’s the new paradigm - neutral drift and universal common descent. What does your analysis of the, the, the data look like ahh to addres that?”*
I would like to propose an exercise for the reader:
Take a look at some of the recent issues of Evolution, Molecular Biology and Evolution, Molecular Ecology, Genetics, Nature Ecology & Evolution, or another journal of your choice that publishes papers in evolutionary biology. If possible, don’t just browse the titles but look at the abstracts and/or full papers (open access papers are usually highlighted as such).
Now, leaving aside the strange and inapt distinction between mutation/selection and common descent, do you agree with Tour’s unnamed geneticist friend that evolutionary biologists are no longer “pushing random mutation and natural selection”, or do you think that Tour, perhaps, should have done a bit more due diligence before repeating what other people apparently told him?
It’s also possible that he misspelled “creationist”. (i) I’m fairly sure that there are at least a few creationist geneticists around, (ii) I’d be unsurprised if Tour knew one of them, (iii) I’d also be unsurprised if one fed Tour this line.
It would be a bit strange if Tour shared Sanford’s claims to Sanford, as though to a stranger. Jeanson might qualify, but I’m sure there are other candidates.
James is referring to me here, and summarizing what I’ve said to him privately. My private conversations with him are well summarized in this interview: Livestream: How I Changed My Mind on Evolution .
This is similar to the case that Larry Moran has been making at Sandwalk for years.
Looking over his quote, I think you are reading too much into it. He has not said that biologists stoped caring about mutation and natural selection. IN context, as well, he is acknowledging where the Dissent from Darwinism did not reflect current understanding in evolutionary science. Perhaps he could have been more precise, but this is just a podcast, not a place where precision is expected.
While I understand the basics of what neutral drift is, I am unsure to what degree is it responsible for the presentation of nature as we find it. I have to admit, as a layperson reading the population genetics discussions here on PS, that I find it confusing as to the extent and means to which neutral drift is held to displace or supplement, invalidate or augment, natural selection.
Not buying this at all. It seems perfectly clear to me that in the context of the discussion he’s having with Sanford, Tour actually thinks biologists have discarded natural selection as a tool for explaining evolutionary change, which can be seen by how Sanford responds to Tour’s statement.
Sanford immediately goes on to put it in the context of the “primary axiom”, that genetic drift would then fail to provide any sort of explanation for “progress” in macroevolutionary change.
Part of the reason that Tour has got this impression is the response of population geneticists to naïve panselectionist arguments. They are quite motivated to point out that one cannot immediately conclude that an adaptation is due to selection on that trait, and they respond by pointing out that genetic drift, migration, and mutation also have to play their roles. However, they don’t understand that the impression that this gives the outside world is that they have given up on explaining adaptations by natural selection. Although Larry Moran is not a population geneticist, he is also eager to point out the importance of genetic drift, and sometimes makes it sound as if he doesn’t think that the ability of an enzyme to carry out its primary reaction has anything to do with natural selection. I’ve been meaning to call him on this some time at Sandwalk and see if he will acknowledge the role of natural selection.
With respect, I don’t agree with this at all. There is no context that can make his statement any close to a reasonably accurate picture of the evolutionary “paradigm”. It is true that evolution isn’t just mutation and natural selection, but mutation and natural selection are critical parts of the process. I don’t know of any evolutionary biologists or population geneticists who would disagree.
It is unfortunate that Tour would make such false statement about evolutionary biology, especially since it’s aimed at an audience that is likely to already hold many false beliefs about the field. I would agree with @glipsnort that he needs to better inform himself regarding the subject if he is going to use his platform to talk about it.
Part of your confusion, I suspect, stems from a lack of a firm consensus regarding the general relative importance of drift vs selection when it comes to the fate of mutations in a population or species.
The following point and counter-point papers are, I think, a fairly good summary of the current debate:
In this perspective, we evaluate the explanatory power of the neutral theory of molecular evolution, 50 years after its introduction by Kimura. We argue that the neutral theory was supported by unreliable theoretical and empirical evidence from the beginning, and that in light of modern, genome-scale data, we can firmly reject its universality. The ubiquity of adaptive variation both within and between species means that a more comprehensive theory of molecular evolution must be sought.
A recent article reassessing the Neutral Theory of Molecular Evolution claims that it is no longer as important as is widely believed. The authors argue that “the neutral theory was supported by unreliable theoretical and empirical evidence from the beginning, and that in light of modern, genome‐scale data, we can firmly reject its universality.” Claiming that “the neutral theory has been overwhelmingly rejected,” they propose instead that natural selection is the major force shaping both between‐species divergence and within‐species variation. Although this is probably a minority view, it is important to evaluate such claims carefully in the context of current knowledge, as inaccuracies can sometimes morph into an accepted narrative for those not familiar with the underlying science. We here critically examine and ultimately reject Kern and Hahn’s arguments and assessment, and instead propose that it is now abundantly clear that the foundational ideas presented five decades ago by Kimura and Ohta are indeed correct.
If I may quote myself from another forum and offer my personal take:
Some points that I think most evolutionary geneticists agree upon:
Natural selection and genetic drift both exert important influences on genetic variation
Many mutations appear to be effectively neutral
What I think there is some disagreement is the relative importance of selection and drift on standing variation and the process of substitution. Even if a mutation is effectively neutral, that doesn’t necessarily mean that its fate is determined by genetic drift, since it is likely to be linked to other (potentially non-neutral) mutations on the same chromosome.
In that case, we have to consider things like the local rate of recombination, the rate of background selection and positive selection, etc.
My guess is that, like most of biology, there is no one-size-fits-all answer. The relative importance of drift and selection may differ greatly in different species, which is pretty fascinating if you ask me.
By the way, since it seems nobody is likely to take me up on my initial “exercise for the reader”, I’m perfectly happy to turn this thread into a discussion of neutral/nearly neutral theory and selection. I’m always up for talking about that!
Looked at couple of journals (just titles, but that’s enough) and would not "agree with Tour’s unnamed geneticist friend that evolutionary biologists are no longer “pushing random mutation and natural selection”. Rather, “Tour, perhaps, should have done a bit more due diligence before repeating what other people apparently told him?”.
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