"The BioLogos website states, “Genetic evidence shows that humans descended from a group of several thousand individuals who lived about 150,000 years ago.”
But Stephen Meyer, a Discovery Institute leader of the intelligent design movement, told WORLD BioLogos leaders are using “an unsubstantiated and controversial claim to urge pastors and theologians to jettison a straightforward reading of Genesis about the human race arising from one man and one woman. They think ‘the science’ requires such a reinterpretation, but apart from speculative models that make numerous question-begging assumptions, the science does no such thing.”
The version of Genesis in my Bible has the creation of humans of undetermined number and both sexes (1:27), followed by what appears to be a separate account of the creation of one particular man Adam and subsequently his wife Eve (2:5-25). That these are separate accounts is obvious from the fact that the relative order of creation is different in both places: the creation of man precedes the growth of plants (and possibly animals) in chapter 2 but follows them in chapter 1. Possibly Genesis 2 refers to a "second" act of creation in Eden specifically: there is no particular reason to believe that the "mankind" of chapter 1 refers to the Adam and Eve of chapter 2, though of course it's a possibility.
Chapter 4 introduces us to Cain, who is scared someone might kill him (v14), implying there are other people around who might do so, who then marries a previously unmentioned woman (v17), and subsequently starts building a city, implying there are plenty of people around who might want to live in it. One possible interpretation is that Adam and Eve had loads of children we simply aren't told about, but another - and it seems to me the more natural one, given chapters 1 and 2 - is to assume that there were a number of other people around separately created by God.
The idea that there existed humans who were not descendants of Adam and Eve is not, therefore, definitely in contradiction to the text and is arguably supported by it. Dismissing anyone who claims otherwise as unbiblical is a somewhat careless thing to do, therefore.