> Although some scientists equate the term "humans" with all members of the genus Homo, in common usage it generally refers to Homo sapiens, the only extant member.
There's no citation for that claim and it would be unlikely for there to be one.
It's just some dude's personal impression about a subjective matter (a word in transition), and carries no more weight than any other comment being made here.
A more meaningful source would be a usage guide like Garner's Modern English.
Actually, it is cited. The fragment you quoted is from the lede, which is supposed to summarize the rest of the material. So if you read on to the section "Etymology and definition", you find that the same claim is cited to Merriam Webster.
As it happens, this citation is useless, because it doesn't support the claim. Basically, I think it's fraudulent to cite that claim to that MW article.
It's just some dude's personal impression about a subjective matter (a word in transition), and carries no more weight than any other comment being made here.
A more meaningful source would be a usage guide like Garner's Modern English.