Fazale Rana has a post responding to the claim that the original human population size was far greater by thousands than just an Adam and Eve. He says the work of conservation biologists, where we can measure the validity of the methods used to determine initial population size (by comparing the methods’ estimations with the known initial populations), can shed light on this:
The methods do appear to be based on sound principles. But that is not enough—not if we are to draw rigorous scientific conclusions. Scientific methods can only be considered reliable if they have been validated….
To my surprise, when I survey the scientific literature, I can’t find any studies that demonstrate successful validation of any of these three population size methods….
In my book Who Was Adam? I discuss three separate studies (involving mouflon sheep, Przewalski’s horses, and gray whales) in which the initial populations were known. When the researchers measured the genetic diversity generations after the initial populations were established, the genetic diversity was much greater than expected—again, based on the models relating genetic diversity and population size. In other words, this method failed validation in each of these cases. If researchers used the genetic variability to estimate original population sizes, the sizes would have measured larger than they actually were.
In Who Was Adam? I also cite studies that raise doubts about the reliability of linkage disequilibrium methods to accurately measure population sizes. Not only is this method not validated, it, too, has failed validation.
Recently, I conducted another survey of the scientific literature to see if I had missed any important studies involving population size and genetic diversity. Again, I was unable to find any studies that demonstrated the validity of any of the three approaches used to measure population size. Instead, I found three more studies indicating that when genetic diversity was measured for animal populations on the verge of extinction it was much greater than expected, based on the predictions derived from the mathematical models.
Dr. Rana goes on to explain some factors not being taken into account by these methods that could explain why they have failed to accurately estimate original population sizes. Read the rest here.