While the Population Today article is interesting, it's impossible to say with any certainty.

It's entirely based upon the age of the Earth, and when the first people lived. If you're a scientist, then you believe in hominids of various kinds including Neanderthals. There's Cro-Magnon, all the side branches including Homo floresiensis, modern Homo sapiens too. It's entirely possible we have other side branches that have never been discovered, as well a possibility that some side branches are happening now.

If you narrowed it down to Homo sapiens, then still, the article is incorrect since it begins in 8000 BCE probably with Sumer, but there's also Gobekli Tepe which predates that, so that blows that out of the water.

Beginning of time is an interesting statement. How do measure that? If you mean, the first day, then the first time the Sun shone and the Earth began an orbit around the Sun, then we're talking back billions of year ago.

Recorded history which you have in parentheses would be probably Sumer not Gobekli Tepe ...maybe.

The question is too imprecise to logically answer. There's no way to know the populations, not in any scientific way.

If you reject Science and choose the Bible then still, there's no way to know. None.

While some people were mentioned, then Abram met Melchizedek, that means the presence of other tribes. We know the children of Adam and Eve later married, and yet this implies other created beings, by logic. The Bible doesn't include a lot of details on this. While some fundamentalist might try to use it as a science book, it's not one.

The question reminds me vaguely of "How many angels can dance on the head of a pin?"
See Thomas Aquinas