They’re just taking an educated guess. Based on fossil records we’ve estimated that homo sapiens sapiens emerged about 200k-300k years ago. I’m not sure if they assumed a middle ground estimate of 250k years here, but it was probably something like that. If we’re measuring by years, the margin of error is huge, but when we’re estimating the total number of people, it doesn’t matter that much, because there were so few of us for so long.
Based on fossil records we’ve estimated that homo sapiens sapiens emerged about 200k-300k years ago.
All of the estimates of when modern humans “emerged” (originally called the “Out of Africa” or “Mitochondrial Eve” hypothesis) are/were based on population analyses of samples of modern DNA (mitochondrial or otherwise) and are/were presented as being in opposition to conclusions based on the fossil record. The original such estimate was 100,000 years ago subsequently revised to 200,000 years ago (both in the mid-1980s) and since then these estimates have been all over the place, ranging from 50,000 years ago to 500,000 years ago. The fossil record shows no significant changes even within this wide time range: bipedality appears in the fossil record for our lineage around 5 million years ago, while our brains enlarged from chimpanzee size to modern human size between 2 million and 1 million years ago.
They’re just taking an educated guess. Based on fossil records we’ve estimated that homo sapiens sapiens emerged about 200k-300k years ago. I’m not sure if they assumed a middle ground estimate of 250k years here, but it was probably something like that. If we’re measuring by years, the margin of error is huge, but when we’re estimating the total number of people, it doesn’t matter that much, because there were so few of us for so long.
All of the estimates of when modern humans “emerged” (originally called the “Out of Africa” or “Mitochondrial Eve” hypothesis) are/were based on population analyses of samples of modern DNA (mitochondrial or otherwise) and are/were presented as being in opposition to conclusions based on the fossil record. The original such estimate was 100,000 years ago subsequently revised to 200,000 years ago (both in the mid-1980s) and since then these estimates have been all over the place, ranging from 50,000 years ago to 500,000 years ago. The fossil record shows no significant changes even within this wide time range: bipedality appears in the fossil record for our lineage around 5 million years ago, while our brains enlarged from chimpanzee size to modern human size between 2 million and 1 million years ago.