Here is what he writes.
(2) Men before Adam. In 1655 a maverick theologian named Isaac de LaPèyrere argued in his book Prae-Adamitae that Adam and Eve were historical persons who were part of a wider human population. God specially selected them to be in relation to Him to fulfill His salvific purposes. Today this view is receiving new attention. So long as there were other people about to interbreed with Adam and Eve’s descendants, there is no problem is holding that everyone alive today (or even at the time of Christ) is descended from an original pair. These two could be located anywhere in the human lineage prior to several thousand years ago. Since our DNA is the product, not only of their DNA, but also of all the other people with whom their descendants interbred, the genetic divergence observed today is no problem. This view is consistent with the archaeological and genetic evidence, but is it really the natural reading of the biblical text?
I hope that he can adjust his language here to recognize that that universal genealogical ancestry is precisely the opposite of LaPèyrere’s polygenesis.