I started a deep ancestry post over a month ago, trying to summarise the radically new stuff we have learned over the last 10-15 years. It was based on a David Reich interview, and couple of people Razib interviewed, plus a long argument an Indian nationalist was having on Substack that I tried to research, because it seemed so counter to what else I was reading.
I gave up. It was 1000 words written, plus a dozen two-sentence clusters that I wanted to expand on, and I had no confidence I was getting it right.
John Hawks, who is an actual expert, addresses the issue in a recent post of his own. Modern humans evolved from an 80-20 mixture of two deep streams. This is not so much Neanderthals and Denisovans, but their precursors, and the admixtures that went into them. Here's what I think you need going in: the 80 is obviously most of who we are, the 20 contains more of what makes us different from Homo erectus and the others. Secondly, over this length of time in the hundreds of thousands of years, 80% of our current genetics does not mean that was 80% of our ancestors in those years. Variations of us that had significant advantages of cognitive fitness might be only 2% of the quantity (of gggggrandparents) of a widespread population, but eventually have an outsize influence. But they would still be highly vulnerable, and the superior disease immunity of a more primitive population would still be hugely important. 80-20 is only a starting point for discussion.
Next, being able to copy tool and technology use is easier than inventing it. The super-bright may have sprung up and died off many times because of disease, while the more primitive hung on because they could at least copy better their technology before they passed into the night. Wiping out a tribe doesn't mean you can't notice they have fishing weirs.
Our ancestors eliminated the people who built Stonehenge, which set civilisation back a thousand years, but that's how ancestry works. Neanderthals had a greater variety of the same tools, suggesting that they were more creative/intelligent than us, but also that they had to reinvent things from scratch more often. Homo sapiens copied the Neanderthals, shared information more efficiently, interbred with them enough to get their best immunity genes, and left them literally in the dust.
Anyway, John Hawks. Great summary, much better than what I could have given you.
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