Estimating populations of ancient humans/proto-humans
March 19, 2013 8:51 AM   Subscribe

I'm working on a musical project and am trying to deal with two big problems entirely outside my areas of expertise. How many species of genus Homo are there and how many of them have ever lived?

The first, how many species of genus Homo were there, is the easier one:

1) The Wikipedia article on the genus Homo lists nine species plus a few extra that we're unsure of. Any opinions on which of these is the most accurate/likely to hold up under further scientific scrutiny?

And now the fun one:

2) What were the total populations of all these folk separated by genus? I see estimates for Homo sapiens that range from 50 - 115 billion. I don't need perfect accuracy (obviously since that would be impossible) but just something rough that's reasonable and also very liberal. So for sapiens I might use a figure like 135 billion. Not crazy high (like 10 superbigzillion) but not likely to underestimate the number (like 51.2 billion). For non-sapiens I understand this will involve a good bit of wild speculation and numbers-out-of-assess-pulling but I'm hoping there are some mefites whose ass-number-pulling will be more accurate than mine.

The nice thing is that the piece, as it's conceived, can be updated as new information becomes available. But I do just kind of need a starting point so any help would be appreciated.

posted by bfootdav to Science & Nature (8 answers total) 3 users marked this as a favorite
I don't particularly know but I did post a Mefi thread about this once: link.
posted by grobstein at 9:04 AM on March 19, 2013

The number of species question is really complicated and controversial. Those species listed in Wikipedia are the species that we have fossil evidence for. There were lots of other species overlapping with those Homo species (temporally and physically - i.e. sometimes there were two Homo species occupying the same time and/or space, as with the Neanderthals and our ancestors, or H. floresiensis and modern humans) but also meaning that there was a continuum of Homo type individuals stretching across time and space - there is no line between most of those species. Different anthropologists/paleontologists draw the line between these species in different places, and they all seem to have VERY high opinions of themselves and will defend their (ultimately arbitrary, IMO) distinctions to ridiculous lengths. They also draw the line between Homo and other hominins in different places, too.

In terms of numbers of individuals, I wonder if that older Y chromosome changes the calculations here or backs them up?
posted by mskyle at 9:14 AM on March 19, 2013 [2 favorites]

Oh sure, mskyle, I get that this is all very fuzzy and full of conflicting ideas, I just need something to start with. I'm guessing that the Y chromosome issue will increase the number of sapiens so I can certainly go higher with that (and in the case of sapiens, leaving room to grow would actually be a feature).

And if I have to I'll just make an arbitrary decision about the species to include. So it's really the numbers I just need some kind of very rough ballpark on. And I get that I'm asking people to treat these very nuanced and subtle concepts as if they were neat little containers probably flies in the face of reason, but I've got to have some upper-limit numbers to deal with no matter how wild the estimates are.
posted by bfootdav at 9:36 AM on March 19, 2013

Well, one nice thing about the confusion is that you could include all of the individuals of the Homo genus without knowing how many actual species there are within the genus and without drawing arbitrary species lines. (Of course, you'd still have to draw an arbitrary line as to what is Homo and what is, say, Australopithecus.)

Is the number of named species and/or the number of individuals within a named species important (e.g. 40,000YA, how many H. floresiensis, H. neanderthalensis, and H. sapiens were there)? Or is the aggregate number what you're going for? And would you want to exclude individuals who were of the genus Homo but were not from a named species?

(Um, I can't answer your question regardless of how you answer the above questions, just saying they're things to think about :)
posted by mskyle at 10:32 AM on March 19, 2013

Bear in mind, scientists vary by orders of magnitude about how many Native Americans there were in 1491, so any numbers would be extremely speculative.

Once humans become top predator, you could perhaps make some assumptions about population density based on geographical carrying capacity, but at the point where human beings are just one of many predator (and prey) animals, I don't know how anyone could arrive at a meaningful answer.

The most you can say with any evidence is that, based on genetics, the people who crossed the Bering Straits were no more than x, and at some point, the entire human race shrunk down to y individuals. But beyond that I'm not sure how the question is even answerable.
posted by musofire at 10:51 AM on March 19, 2013

The population numbers are essentially nil for everything other than homo sapiens and (possibly) neanderthals. I think the current theory is that from about 1.2 million years ago until 200,000 years ago there were very few individual humans. Say 20-30,000. Assuming a 20 year generation (because it makes the math easier), I get about one billion individuals who lived during that time. Dividing them up is going to be more difficult.

Homo habilis? Beats me. They were around for about a million years and even if we assume there were 10x as many, that still gives us only 10 billion individuals. IOW, not many.

Your numbers for homo sapiens match my recollection.

I'm not even remotely an expert on this subject, btw.
posted by It's Never Lurgi at 11:51 AM on March 19, 2013

Thanks everyone for your help so far, so please bear with me. I will try to simplify the request some more. Setting aside sapiens for the moment, what about an aggregate number for all of the genus Homo? Let me start with this range: no less than 10,000 but no more than 1 quadrillion. Can that range be shrunk any more? Say more than a million but less than a trillion? 100 billion? 10 billion? Any large upper-limit would serve my purposes (I would rather err on the side of having too large a number than too small of one). I just don't want to be stuck dealing with a number like 1 quintillion if a better answer is several orders of magnitude smaller.

And if this number cannot be reasonably divided among the species then I will choose a method to weight them based on range of the fossil record, number of fossils discovered, ages, number of words in the respective Wikipedia article, etc. which will be good enough for my needs.
posted by bfootdav at 11:53 AM on March 19, 2013

I once did some research into the number-of-people-ever-lived question, and I can tell you that a couple of the original estimates in your range were calculated starting the count as much as 2 million years ago, i.e. they were including non-sapiens humans in the count. You would be fine picking a number in that 50 billion to 115 billion range and weighting it somehow as you say (someone else will have to supply the calculus or whatever needed for that).
posted by gubo at 3:04 PM on March 19, 2013

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