It is easy to have misleading intuitions about the population genetic effects of a short, sudden bottleneck. For example, Ernst Mayr suggested that many species had passed through extreme bottlenecks in founder events. He argued that extreme loss of diversity in such events would promote evolutionary change.
The matter was taken up at The Skeptical Zone where population geneticist Joe Felsenstein, among others, replied, skeptical but not ruling the idea out.
Now Buggs has replied at the Zone to comments by Felsenstein and Schaffner:
First, I note that both Schaffner and Felsenstein agree with my point that the bottleneck hypothesis has not been directly tested.
Schaffner: “Buggs is right that existing tests have not been tested rigorously against an ancient Adam and Eve scenario. On the other hand, no one has shown that such a scenario would be undetectable by those tests either; it’s just not a scenario most geneticists are interested in.”
Felsenstein: “Most of the effort in analyzing these data has been to infer the past history of population size, rather than to make statements about A&E.”
Felsenstein goes further than this and suggests that it could never be entirely disproven: “If one poses the problem as whether we can absolutely certainly rule out A&E, that is asking for more than science can deliver. But if we ask whether it is made very improbable, that is not as hard to establish.”
Second, I note that neither of them are defending the PSMC argument, and Felsenstein implies that it is not necessarily reliable and new methods need to be developedMore.
In short, we don’t know that a single human pair Adam and Eve, could not have been the human founders unless we adopt a theory to which evidence is irrelevant. Cosmology’s multiverse springs immediately to mind but does evolutionary genetics want to go There?
Note: At odd moments in these times, biology sounds more sensible than physics.
See also: Adam and Eve debut at the Skeptical Zone: In other words, we don’t really know if they could have existed because the human race seems very improbable anyway. But it is high time the question was liberated from the Sunday armchair of theistic evolution, to say nothing of its occasional personal dramas.
Geneticist defends possible Adam and Eve in Nature: Ecology and Evolution
Geneticist: Adam and Eve could have existed