Just was watching Dwarkesh/David Reich podcast, fascinating stuff. Looking back at how I was taught taxonomy and anthropological history I find it frustrating. Note that I don’t know much about (evolutionary) biology or genetics or the frontier of what genetic-history research so this is my layman attempt to explain why it’s generally been puzzling for me how i have had this explained by other people who probably don’t understand either, not trying to propose that I understand something david reich doesn’t.
My main gripe is that we are taught evolutionary history mostly from the lens of evolutionary trees. But evolutionary history probably looks like a graph/stochastic process/markov chain, and only at very specific underlying parameters/ level of abstraction is well modeled by a tree. The reason we use trees is because that is the most sensible simple abstraction in some ways, if you are thinking about, “how did we get here?”. But it’s not a great way to think about “what happened/was happening”. I had chatgpt try to make the difference below (don’t look too into the details, it did some hallucinating, just the general vibe).
Taking plausible parameters here to me would be thinking mixture isn’t extremely likely over short time spans because of distance/etc but quite likely and almost certain over hundreds/thousands of years. So what did the near east look like genetically 60k years ago? It could easily look like below.
It seems totally possible that for long periods of hominid history genetics were well modeled by pretty smooth stochastic graphs with generally corresponding smooth genetics across geography (obviously with tons of exceptions or less true when you zoom in, e.g. bell beaker/corded culture), and yet when you look at our specific lineage it doesn’t quite look like that (due to extinction, gene selection, or some other reason). I don’t have a clear enough vision to say much more, but I think there are some interesting implications about what we mean when we say, this group or that group went extinct.
Just was watching Dwarkesh/David Reich podcast, fascinating stuff. Looking back at how I was taught taxonomy and anthropological history I find it frustrating. Note that I don’t know much about (evolutionary) biology or genetics or the frontier of what genetic-history research so this is my layman attempt to explain why it’s generally been puzzling for me how i have had this explained by other people who probably don’t understand either, not trying to propose that I understand something david reich doesn’t.
My main gripe is that we are taught evolutionary history mostly from the lens of evolutionary trees. But evolutionary history probably looks like a graph/stochastic process/markov chain, and only at very specific underlying parameters/ level of abstraction is well modeled by a tree. The reason we use trees is because that is the most sensible simple abstraction in some ways, if you are thinking about, “how did we get here?”. But it’s not a great way to think about “what happened/was happening”. I had chatgpt try to make the difference below (don’t look too into the details, it did some hallucinating, just the general vibe).
Taking plausible parameters here to me would be thinking mixture isn’t extremely likely over short time spans because of distance/etc but quite likely and almost certain over hundreds/thousands of years. So what did the near east look like genetically 60k years ago? It could easily look like below.
It seems totally possible that for long periods of hominid history genetics were well modeled by pretty smooth stochastic graphs with generally corresponding smooth genetics across geography (obviously with tons of exceptions or less true when you zoom in, e.g. bell beaker/corded culture), and yet when you look at our specific lineage it doesn’t quite look like that (due to extinction, gene selection, or some other reason). I don’t have a clear enough vision to say much more, but I think there are some interesting implications about what we mean when we say, this group or that group went extinct.