Yes, I have thought about that! =)
If you allow for interbreeding all bets are off. Adam and Eve could have been 10,000 years ago in the middle east, or 200 kya as the sole-couple progenitors of Homo sapiens, etc. None of the genetic work we have done here has any relevance to the question if interbreeding is allowed.
That’s about right, but do not forget Denisovans.
#2 is pretty strong too, as it is very easy to explain to non-experts, and is also very well supported in the data.
That is not really relevant to our question.
We have only 1 Denisovan genome (from a single knuckle, now destroyed), and do not know of we descend directly from this Denisovan. It is possible that Adam and Eve are our sole genetic progenitors, but some Denisovans interbred with another hominem, then subsequently died off without ever contributing to all of us. Unless we can show that those genes appear in humans too, and do not push the TMR4A back, then it does not give us a confident way to push back our date.
They also give an alternate hypothesis:
The issue is that we cannot actually untangle this knot in most cases. In extant scenarios, migration can only measured by getting serial measurements over time and comparing them. Without serial measurements (multiple time points) its not possible to determine the direction of interbreeding events, or distinguish it from incomplete sorting. This, therefore, is just not strong evidence against a bottleneck at 500 kya - 700 kya.
That has never been done. But also we have no way of parsing out what is what that far back.
I agree that this will always be subject to revision. However, it is hard to imagine the evidence what would pull the date back earlier than 2 mya. The most likely thing, I would guess, would be trans species variation, having ruled out convergent evolution. To do that, we would need to get a much better census of great ape genetic variation, and do a very careful (and frankly difficult) analysis to make sense of that. Still, it is possible that at a future date a single couple of bottleneck would be ruled out.
Then, however, if we allow for interbreeding (whether it be sanctioned by God or not), all bets are off. We do not think a single-couple origin of our kind needs to correspond with a single couple bottleneck.
As we have shown, if we allow for interbreeding, all bets are off. Adam could be very recent, or at the origin of Homo sapiens, or really any where or time we like.
How would this reconcile with @agauger? Well, that requires theological reflection. If we’d like to change @agauger’s view of this, it would probably be best to engage catholic theologians and philosophers (e.g. @AntoineSuarez).