Ah - “Statistical Analyses are the assurance of things hoped for, the conviction of things not seen.” (Heb 11:1, American Scientistic Version)
“The epidemiologist fallacy is also richer than the ecological: it occurs whenever an epidemiologist says, “X causes Y” but where he never measures X and where he uses classical statistics to claim proof of a cause - based on, say, wee p-values or large Bayes factors; [citation]. Over-certainty is guaranteed.” (William Briggs)
X, in this case, is the original ancestral population that gives rise to the population we have now, which we are trying to ascertain and which we cannot measure, even if we want to. If we really can, through models alone, allow for all the factors that we don’t know we don’t know, then science is back to the Greek model, where reason replaces empirical examination of the world.
Unknown Martians are an unlikely factor here, in my humble view. But unknown biological mechanisms, and unknown historical contingencies, are not only likely but turn up every year - what do we know now from actual data about the radiation of humanity that we did not know this time last year? Wasn’t “Out of Africa” not long ago an uncomplicated and more or less uncontested understanding of where we came from?
One possible confounding factor for this particular discussion, as regards the final truth of the matter, is the ultimate point at issue (correctly excluded by Richard for the scientific discussion) - a known God who, according to many following the traditional understanding of the Scriptures, created the first humans as a single couple de novo.
I have no dog in the fight - I don’t believe an Adam >200K years ago is consistent with Genesis. But I do know that once one has done the excellent modelling that Joshua, in particular, has worked on, then what one has achieved is a fuller exploration of the model(s) currently in use, and a bigger range of possibilities than was previously thought - but by no means a certainty about the deep past on which to stake your life.
Or even a reliable quantification of what surprises the world may have for you.