If that statement appeared out of nowhere, there would indeed be ambiguity and two ways to take it. However, it did not, and within its original context, it is very clear which way it was meant and it is not false at all.
I will give you that substituting in ‘Homo sapiens’ lends emphasis to your alternative meaning, because another way to tell how to parse a sentence is to look for the most specific words (‘two’ is more specific than ‘people,’ but ‘Homo sapiens’ is more specific than either) but that is no reason to change our established understanding of the sentence: We do not descend from only two people. (We evolved as a population.) I’m sorry but it’s more than adequately clear.
We don’t care at all how some arbitrarily defined population of Homo sapiens begins; we care if we are descended from a single couple and only a single couple. That is the topic of discussion. Is there or is there not a single couple from whom alone we all descend?
I am not qualified to converse at as high a scientific level as Dennis Venema and Richard Buggs. It’s great that you are qualified, and have provided a lot of very valuable contributions to the discussion. But if you’re going to pursue this issue of grammar as you have been doing, I do consider myself qualified to disagree with your conclusions as I have been doing.
I have not seen anyone else take the meaning from the statement that you do. If McKnight did and disagrees with your genealogical Adam on the grounds of it, I will be extremely surprised: I think it more likely that there is some other miscommunication happening there. I don’t know if you’re referring to a public conversation or a private one?