Gregory's ServerA new study has found a terrible bottleneck in human ancestors about 900k years ago. There were as few as 1000 individuals left ... if this is verified further there was a time when we almost didn't make it.
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@futurebird 117 thousand years with only a little over one thousand individuals? Damn. How common is it for species to stick around that long with such a low population?  @aspensmonster @futurebird I dunno, but after learning how mutational meltdown killed off the last mammoth population, the fact that our ancestors survived this (assuming it holds up) sounds even more absurd @aspensmonster @futurebird There have been other severe bottlenecks, and they are shockingly recent. As a result, homo sapiens’ genetic diversity is very low. One thing that racists get wrong is that human inter-racial genetic diversity is simply too low to support their claims. Our diversity relative to our geographic distribution is absurdly low. Genetics-based racism isn’t just morally wrong, it is radically wrong about our reality as a species.  @bertwells Except actual Nazis, I think most.of the racism has moved to skin color, and particularly culture. Black culture, indigenous culture, Hispanic culture, Jewish, Romany, etc. And universally it seems a bucket of anyone Muslim, from Rabat to Jakarta @aspensmonster 1280 is the nadir but it looks like they're positing that the 117k period started at the 100k-ish original pop, fell to 1280 at some point, then rose to the 27k-ish pop by the end of that period. It wasn't 1280 for the whole 117k years. But that's from the graphic, not reading the paper @aspensmonster @futurebird I would assume there are quite a few birds on islands who live that Life 😄  @futurebird Fascinating, I look forward to the confirmation and debate. (For the record, we've got 8 billion or so, now, and I regard *this* as a time when we're likely not gonna make it.) @GeePawHill @futurebird Oh, humans will survive this. We live in more environments than roaches, and there are eight billion of us. How many will remain though? I've read convincing articles showing that the carrying capacity of the planet without fossil fuels is around half a billion, and that's before we render the tropics mostly uninhabitable... Not having kids is a great way to prevent then from dying in the water wars. 💔 @TomSwirly @GeePawHill @futurebird  @futurebird @yanncphoto @levpetrovitch @futurebird I heard that they were during the bottleneck, according to the last count, 1337. @levpetrovitch @futurebird can you accept estimates that have some statistical uncertainty about them? To me, 1280 could mean 1279-1281, or 1000-1500. Either way, the “precise” number is probably the centroid of their estimate. Confidence intervals usually don’t make the lede. @vanderZwan @levpetrovitch @futurebird That still doesn’t work: Everyone whose line ended up dying out by definition has not left a trace in our DNA. Was that almost nobody? 10%? 50%? 90%? There may even be ways to approach the answer to that, but they are by definition not in our DNA and bound to be highly imprecise. @vanderZwan @levpetrovitch @futurebird And while I can absolutely buy that the human population was terrifyingly low at times (I believe I remember something that it may have gotten to the very low double digits at some point, creating insane evolutionary pressure), I have a much harder time to believe that it was possible to maintain these insanely low numbers for the kinds of time-periods that we are talking about here. Over 100000 years at a population of of ≈1000 people seems very implausible to me. @Fiona @levpetrovitch @futurebird well this paper is not exactly tracing lineages, it's tracing genetic drift across fifty populations, sampling about 3000 people. So it looks at the accumulation and spread of new mutations. Of course I don't know how one makes the jump from genetic drift to population size estimates, let alone population size estimates over time, so no clue on what precision to expect there. @Fiona @levpetrovitch @futurebird aww, that's too bad but I completely understand. I will just imagine the best quality slides then. @Fiona @levpetrovitch @futurebird (I'm just having fun speculating, don't take this seriously) I suspect it might be possible to get an estimate of how quickly lineages die out by comparing genetic drift in Y-chromosomes, which don't recombine, to the other chromosomes which do. Because the rate at which genes are filtered out of the population should be different for "gene that can only be passed father-to-son" vs "gene that can be passed any-parent-to-any-child". @levpetrovitch Studies like this are very useful, but they should never be taken alone as some proof of an idea. Further evaluation and validation is needed, preferably from unrelated areas. A reminder that this is how the Toba bottleneck theory began, with a single proposal and a public acceptance that it must be true because it was a science paper. Later archeological findings put the theory as a global bottleneck into doubt. @levpetrovitch @futurebird I must admit, the number of significant figures seems remarkable. I would love to know if this study truly was this specific, and to be smart enough to follow the process they took to get there.  @levpetrovitch @futurebird I'm waiting for the Creationists. They'll surely have some fun with this. @futurebird Person of the Bottleneck Era, comforting a friend who’s going through a bad breakup: “You’re better off without them, really. And don’t worry, there are a lot of fish in the sea.” Friend, sniffing back tears: “No, there aren’t. There aren’t very many at all.”  @gorfram @futurebird This doesn’t freak me out too much - in fact it’s relatable. This Bottleneck kind of describes what it felt like growing up and living in Ireland. 😄 @MarkMaguire @futurebird I was raised a Quaker, & one time I did the math on why so few Young Friends married other Quakers. Of all the Quakers I knew of (probably around 1280 or so 🤣) at least half were women, the vast majority were middle-aged or older, & some were the middle aged-ones’ children. Of the few guys in the suitable age range, a large % were either gay or taken or my brother. That left… four. One of them I kind of disliked; & the other 3 seemed unlikely to like me in that way.  @futurebird A 2012 study found another bottleneck era 70,000 years ago. @futurebird IMO, bottlenecks like these are both interesting science and inspirational topics to go into with students. In studying them, it is possible for every student in the class to hear a message: “We are all descended from a small group who kept humanity alive through unspeakable extinction level conditions. Every single one of you is a direct heir to the most baddass people who ever lived.”  @futurebird really interesting, thank you for sharing! Made me speculate about another possible bottleneck coming up and the terrifying prospect of really only billionaires in bunkers and their offspring (already plentiful, Musk and others have 10+ children) surviving and a distant future with everyone descending from those!  @pvonhellermannn @futurebird I thought about that too. A bunker is also a prison though and what emerges is going to be interbred, and unaccustomed to what remains of the earth, probably take more time to help them than it would to defeat them.  The road not taken. I wonder what would be the dominant species in that alternate possibility. Any thoughts? Dolphins? Cave Lions? Mastodons, of course!  @superball @NoctisEqui @futurebird Well, we're both dominant and submissive, so it evens out 🤪 We're the dominant species in a "whomever has the power to destroy a resource controls it" kind of way. We *definitely* have the power to destroy the biosphere @futurebird I'd heard about that years ago, but it was pre-internet. Thanks for the article, I've always wanted to know more about it.  @futurebird When you have a large breeding population, a lot of beneficial mutations can simply get "washed out" in the gene pool. It's still super cool information. We know so much more about distant human history than we ever thought we would. @futurebird Yeah, but on the other hand, at that time it was easy to get some peace and quiet in this place. @futurebird I’ve seen previous suggestions that, at one time, the global human population dropped to the point that they couldn’t fill Soldier Field and honestly? I kinda want to believe it, selfishly. 1/x Like, if our hairy ancestors could survive and come back to an 8bn population after some catastrophe like the Chixulub Impactor knocked them back to the size of the line for Taylor Swift tickets when she plays Madison Square Garden, it gives me hope in the face of climate change and Stage IV Capitalism. 2/x “Sure, things look bad but we bounced back before and back then, our tech tree maxed out at Tamed Fire, Wheeled Cart, Pointy Stick, and if you beat the secret level, Domesticated Dog.” I kinda need that hope right now. I’m like, “Yes! Hope! Inject it straight into my gumline, I don’t care, I’m fiending for it!” 3/3 @futurebird Could it be possible that the inbreeding resulting from that bottleneck was the cause of so many diseases today? 🤔 It's been a long time since then so maybe not? And 1000 is just enough to get by without it getting too bad. @futurebird What really saddens me is that we lost the ability to produce vitamin C. God save us if all citrus in the world are lost.  @yuki2501 @futurebird That’s a good target for CRISPR or other genetic engineering, as (I believe) it is controlled by a single gene in primates.  @futurebird I mean it was only what 6,000 years ago we were down to the 2 Adam and Eve did I get that right   @futurebird This seems to coincide with the "missing link" time range - kinda remarkable. I also wonder what might have happened. Was it ecological? Did they have fire? Maybe we'll be sure one day. Right up there with the Toba extinction 70-75,000 years ago that blacked out the sun for nearly a decade straight and left small clusters of breeding pairs available, nearly ending the species. The unsettled period on the planet was really bad for us all.  @futurebird 'great filter' candidate? just from the statistics? very interesting!  @futurebird I've sometimes wondered if our weird investments into brains might have been driven by a prolonged period of having to move from niche to niche without time for physical adaptations to really pay off. People tend to think brains are great, but in the animal kingdom in general, it seems brains are ranked below a really effective digestive tract in terms of evolutionary payouts.  |
@futurebird
As I've said elsewhere that means we probably won't go extinct in the next few millenia. But without a global technological civilization we may wish we were.