swamidass
November 8, 2019, 4:55am
8
Yes I agree. No where did I say anything that disputes or misrepresents this.
You go up to any person on the street and ask what a human is, you know they will respond by saying us. That book was written for that audience.
That actually is not true. That is not the common understanding at the moment.
Even if it were true, it is misleading to insist on that definition. Moreover, he does not present any evidence that demonstrates Homo sapiens do not dip down to a single couple. Instead he presents evidence that our ancestors as a whole don’t dip down to a single couple. These are very different things!
Of course you must know this already:
On face value, we know that this cannot be known with certainty. Some scientists are not even sure if the remains earlier than 300 kya are fully Homo sapien . That means it is entirely reasonable to believe that Homo sapiens go to zero
Where is the error? The inference that (1) our ancestors never go below a few thousand, so therefore (2) Homo sapiens never go below a few thousand, is an example of the Ecological Fallacy. What applies to a group of things (the group here is “our ancestors”) does not necessarily apply to all the individuals in that group (the individual here is “Homo sapiens”).
To be 100% clear, this is not at all a challenge to mainstream population genetics, which makes claims about our ancestors as a whole. All the population size estimates (which are geometric averages over a time window) all include Homo sapiens + others , as far as I know. As far as I know, no one has found a way to figure out what the ratio is between the two population is; nor has anyone asked the question in a research study.
It is entirely possible that at sometime in the distant past, the total number of breeding Homo sapiens is precisely two, even though the total number of our ancestors at the time would be much more. Eventually, these early Homo sapiens would interbreed with others. This is an example of a hypothesis that (1) directly contradicts @DennisVenema ’s claim, and (2) appears entirely consistent with the evidence, as I understand it (and I’m happy to be corrected). If any such hypothesis exists (and I think I’ve just demonstrated one), then Dennis’s claim is false.
The problem is not the findings of mainstream population genetics at all here. The problem is rather in the inference from this finding to the claim that this means Homo sapiens never dip below a few thousand. If we go back far enough their numbers go to zero. If they can go to zero without contradicting the evidence; so why can’t they go to 2? (of course, the would be interbreeding with surrounding non-sapiens).