I’ve been proven wrong. Sometimes, after seemingly endless conversations on Internet message board threads, something important really is learned definitively by the participants. I was highly skeptical that this could happen. But following a looooong discussion of 1,000+ posts on the BioLogos message board, it did!
I offer sincere congratulations to all, and apologies for doubting you. The challenge then becomes to retrieve that something from the tangle of words and present it clearly.
In his book Adam and the Genome, BioLogos “Fellow of Biology” Dennis Venema sought to persuade his fellow Christians that genetic science had disproven the traditional idea of a “bottleneck” of two human ancestors in the near or very distant past. Why the somewhat opaque Evangelical Christian BioLogos organization seemed wedded to slamming their own tradition this way has been to me, an outsider and student of human nature, a fascinating puzzle. But now Venema himself indicates that he’s out in his former capacity at BioLogos, and he is no longer listed as the Fellow of Biology. So perhaps things will change.
The main players in the discussion include geneticist Richard Buggs of Queen Mary University in London, biologist Ann Gauger of Discovery Institute, computational biologist Stephen Schaffner at the Broad Institute, computational biologist Joshua Swamidass at Washington University, and of course Dr. Venema.
Over all, this was a highly substantive and educational debate. Bottom line: Venema has backed down. At post #1063, he replies to Buggs.
You would do your readers a service if you wrote a blog to tell them now, as far as you are able, that present day genomic diversity in humans does not preclude a bottleneck in the human lineage between approx 700K and 7myr ago. I think you owe this to them, and to everyone who has taken the time to participate in this discussion.
That is, Venema should concede in an official BioLogos blog post that contrary to the apparent main point of his Adam and the Genome, genetic science DOES NOT exclude a traditional first couple, capable of being identified with Adam and Eve, somewhere between 700,000 years ago and 7 million years ago. Venema notes that the “official” BioLogos online space is, apparently, no longer his forum in which to so. But he does concede:
I’ve already agreed with this, and it’s been up there ^^ for weeks now. You’re welcome to publicize it as you wish. I no longer write in an official capacity for BioLogos, except by invitation from time to time. This means I’m just another commenter like you for the time being.
I don’t know what comment Venema is referring to, and I suppose Buggs doesn’t either, otherwise he wouldn’t have asked. I’m not going to wade through the one thousand sixty two comments that come before to search for it. But the point is that Venema now agrees with Buggs.
Not a Question of Merely Scientific Interest
Ann Gauger had written in her own concluding remarks, directed to Dr. Venema:
I support what Richard has said. It is clear that when you wrote Adam and the Genome you were taking the published literature at its word, most of which said our population at the time of our split from chimps had an effective population size of 10,000. This seemed solid, as a number of different analyses yielded similar numbers. However, you made an extreme claim when you said that the certainty we could not have come from a bottleneck of two was as certain as heliocentricity.
Why this went wrong should be a lesson to all scientists: it is dangerous to extrapolate or over-interpret data, to go beyond what has been explicitly tested. No one had explicitly tested a bottleneck of two; it was the received knowledge that of course we couldn’t have come from two. Evolutionary theory said species were formed by progressive differentiation from an ancestral population. The claim was made that current genetic diversity could not be explained under standard assumptions if the species started from two. And that is true for recent origins. Standard assumptions won’t work for a young origin of two. Therefore it was not even worth examining, most assumed. But that conclusion was wrong, as we have seen.
Richard gave a very good summary at [LINK].
Because the claim that we could not have come from two is wrong, and because that claim impacts the faith of many Christians, with corresponding doctrinal effects, it would be very helpful, even important, to set the record straight. This is not just a matter of a scientific dispute. All we are asking for is a public statement something like this: In a prolonged discussion with my colleagues it has become apparent that the claim that we had to originate from a population of 10,000 was never sufficiently or completely tested. Further analysis has indicated that it is possible that we could have come from a bottleneck of two. [Emphasis in the original.]
We now have the “public statement” from Venema, which is more like a squeak, though, than the robust admission of error that Buggs or Gauger sought. So be it.
What’s the “good summary” from Buggs? Gauger is referring to a post by Richard Buggs for the forum associated with the journal Nature Ecology & Evolution, “Adam and Eve: lessons learned.” This is interesting. A major geneticist observes that his broaching this question at all “may sound bizarre to some,” but “it is one that is often asked by those with a background in Abrahamic faiths.” Following the discussion about Adam and the Genome, Buggs concludes that that matter remains up in the air. Yet the debate has shifted significantly:
To my mind, the question has now moved on from “Is an ‘Adam and Eve’ bottleneck inconsistent with human genetic diversity data?” to “At what timescale could an ‘Adam and Eve’ bottleneck be consistent with human genetic diversity data?”
Having rejected Venema’s contention that a first couple is excluded, the problem becomes “at what timescale” are they not excluded. In other words, as I understand from the circumspect language, when might they have lived? For a scientific debate with profound theological implications, that is a major evolutionary leap.
Look Before You Leap
To be sure, Venema hasn’t completely abandoned his position. He still clings to what Buggs, quoting Dawkins, calls an “argument from personal incredulity.” Venema:
Unless I’ve missed it — and I might have — I have not seen you propose any mechanism for a precipitous drop to 2 followed by exponential population growth. I don’t see this as plausible.
This is an “argument from personal incredulity” (to borrow a phrase from Richard Dawkins). I am interested that this now appears to be your strongest argument against a bottleneck. I suspect that many people will find this argument less compelling than the “certain” case from population genetics that you appear to make in Adam and the Genome.
As far as I can see, a step-by-step evolutionary pathway for a lineage passing through a bottleneck is clear, and you just have doubts about the selective forces that could drive it. As arguments from personal incredulity go, that is not a very strong one.
Mothers don’t easily abandon their babies, and Venema is not abandoning his book, either. That is only natural for an author. But he does try to spin things in his own defense:
In AatG I defend two claims — (1) that as our species, Homo sapiens (anatomically modern humans or AMHs), comes into being, we do so as a population. This is the “heliocentric” quote.
I also say that (2) the dip to ~10,000 seems to be the lowest our lineage experienced over the last 18 MY, based on the methods applied to date.
Both of these statements remain accurate.
Buggs won’t have any of this:
I am sorry, but I don’t think this is a complete summary of your claims in Adam and the Genome. You made very specific claims about what the literature was saying, and these have not stood up to scrutiny.
In addition, I think that most readers of Adam and the Genome pp45-65 would conclude that your major claim was that a bottleneck of two in the human lineage is almost impossible on the basis of analyses of current human genetic diversity.
But we have discussed these issues before, and anyone can read your book and make up their own mind, so I won’t belabour the point….
What we have established is that a very sudden bottleneck to 2 followed by exponential population growth might escape detection using current methods if it occurred before 700,000 years ago. That is interesting, but it does not change the points I made in the book.
There’s a Monty Python sketch for almost every occasion, isn’t there? Venema, under pressure, appears to have changed his claim. Buggs:
As I say, I think that most readers of Adam and the Genome pp45-65 would conclude that your major point was that a bottleneck of two in the human lineage over the last 18 million years is almost impossible on the basis of analyses of current human genetic diversity. Your new view is a significant departure from this point.
And so it goes.
For your reference, final statements from the participants can be found as follows: Venema, here and here; Swamidass; Schaffner; Gauger; and Buggs, here, here, and here. I think at this juncture it’s reasonable to set Venema and his book aside at last.
What’s really needed is a statement not from him but from BioLogos, an influential group that, in a partnership with the John Templeton Foundation, has been dedicated to talking Christians out of long-held beliefs in favor of Darwinian evolutionary ones. The issue isn’t solely of scientific interest. As Ann Gauger points out, it “impacts the faith of many Christians,” and she has noted how students in Dr. Venema’s own classes have experienced that fact. On Adam and Eve, has BioLogos changed its claim? It would be good to find out.
Photo credit: pasja1000, via Pixabay.