[HN Gopher] Modern genetic data suggests pre-humans were a group...
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Modern genetic data suggests pre-humans were a group of only 1,280
individuals
Author : geox
Score : 84 points
Date : 2023-08-31 21:08 UTC (1 hours ago)
(HTM) web link (www.nature.com)
(TXT) w3m dump (www.nature.com)
| swader999 wrote:
| And I thought high school was tough.
| svnt wrote:
| The idea of (at least one) population bottleneck in the
| evolutionary history of humans is fairly widely accepted. I
| haven't reviewed the paper or methods but generally their results
| fit the range of expectations of many in the field.
|
| This new paper is interesting in that they developed a new method
| in population genomics specifically to attempt to pin down all
| of: the time, the duration, and the size of the population.
|
| There are many earlier papers describing different methods for
| arriving at similar conclusions. The below paper used similar
| genetic signatures from bottleneck events such as the loss of
| rare alleles. Their methods were different. It explains one such
| process fairly well and is available to read:
|
| https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2842629/
| jokoon wrote:
| Which is why humans are very sensitive to interbreeding
| kibibu wrote:
| Would have saved everybody a lot of trouble
| cubefox wrote:
| Many were increasingly of the opinion that they'd all made a
| big mistake coming down from the trees in the first place, and
| some said that even the trees had been a bad move, and that no-
| one should ever have left the oceans.
| delta_p_delta_x wrote:
| In the beginning the Universe was created. This has made a lot
| of people very angry and been widely regarded as a bad move.
| bradneuberg wrote:
| Ok Doomer!
| patall wrote:
| You are joking, but still: this was likely not the only group
| of humans in existance, just the one that became us.
| [deleted]
| lainga wrote:
| The romantic optimist in me will keep some hope out that that
| sort of thing was the Great Filter which felled so many of our
| unseen galactic neighbours.
| api wrote:
| The Great Filter is really just an arbitrary speculation since
| we don't know most of the parameters in the Drake equation with
| any certainty.
|
| It's also a fallacy to assume that a great filter, if it
| exists, must be a single discrete climactic test or have a
| single explanation. It could be that there exists on average a
| continuous low probability of an event or evolutionary path
| that rules out advanced intelligence in a given biosphere.
|
| Let's say that the yearly probability of such a terminal event
| or path is about 0.00000002%. Over 500 million years this would
| amount to a 99% chance of failing the great filter.
|
| If this is true it would mean that we're almost there, very
| likely to succeed, but also very likely pretty alone at least
| in our galaxy since there won't be that many advanced
| intelligences around.
|
| The difference though is that unlike the discrete great filter
| hypothesis there is no single apocalyptic event to fear. It's a
| small probability spread over aeons.
|
| This is just to show that we don't know the answer to the Fermi
| paradox at all. There's no testable or scientific answer at
| least. Only way to really know is to go out there and look
| around.
| borissk wrote:
| There may be 99% chance of failing the great filter in the
| 500M years before an industrial evolution and 99.99999999%
| chance of failing it in the 10K years past. Humankind
| invented nuclear weapons and had a lot of luck that they are
| hard to make and so far only 2 were used in anger. There's a
| good chance that with the progress of AI, nanotech, CRISPR
| very powerful weapons will become available to groups like
| ISIS - greatly decreasing humankind's chances of survival.
| Aardwolf wrote:
| It's pretty crazy to think about this: if a generation would be
| 25 years on average, only 5 million individuals lived during
| those 100k years. But today, 100k years in the future sounds like
| a 100x longer time than what would already be unimaginable
| science fiction...
| aap_ wrote:
| Imagine this: watch two years of the life of every human alive
| today. You'll need more time than the age of the universe (as
| far as we know).
| leafmeal wrote:
| Crazy to think about! Minor correction: 5 million reproduced,
| presumably more lived but died young, etc. but you point still
| stands
| titzer wrote:
| No, it doesn't mean that. The bottleneck doesn't say anything
| about how many people were alive then, just how many
| contributed DNA surviving until present day. There could have
| been millions of individuals whose offspring eventually ended
| up as genetic dead ends and we'd never know, except for
| fossils.
| kzrdude wrote:
| That perspective - is why we can say that we live in a very
| busy world right now. So much human life going on at the same
| time in this moment. A lot more than compared with 100k, 10k,
| 1k and 100 years ago.
| calimoro78 wrote:
| Fair to say most of humankind's time then has been spent
| staring at small digital screens.
| dtx1 wrote:
| Remember that Black Monolith in 2001: A Space Odyssey? 1280
| Individuals is in the realm of what some alien mission could do
| in terms of genetically a bunch of apes to become smarter
| titzer wrote:
| Headline is misleading. The existence of a population bottleneck
| of approximately 1200 individuals does _not_ imply that humans
| almost went extinct. It doesn 't say anything about the size of
| the population before or after that bottleneck. In fact, it
| doesn't even say anything about the size of the population _at
| that time_. It just means that those 1200 individuals are the
| only ones that have contributed genes to the gene pool that
| survives today. There could have been other human populations
| that did not pass on their genetic material to modern humans, but
| were the same species as those who did. In fact, there could have
| been a lot of them. There were many different hominid species
| alive at that time, and humans were in competition with them. We
| have no idea of their relative number. It could have been
| millions for all we know.
|
| Absent any other evidence, a population bottleneck (derived
| through studies of live human DNA) suggests _nothing_ about the
| population at the time, or over time.
|
| Survivor bias.
| daveguy wrote:
| Yes. The number of breeding pairs present at one time could
| have coincided with a large population of human-like creatures
| that went extinct.
|
| The key point in your phrasing is: "There were many different
| hominid species alive at that time, and humans were in
| competition with them."
|
| If humpback whales eventually become extinct and blue whales
| eventually dominate global ecosystems we aren't going to say
| that means blue whales didn't experience a near extinction
| because "hey! plenty of whale-critters".
|
| A minimal number of breeding pairs _is the definition of near-
| extinction_. To imply otherwise is misleading.
|
| Homo-sapiens is not the same as Homo-neanderthalensis.
| borissk wrote:
| This bottleneck occurred before the split between "us" and
| neanderthals - so if this small population didn't survive
| there wouldn't be not only modern humans, but neanderthals as
| well.
| daveguy wrote:
| Ahh, yes. Good point. Neanderthals wasn't a good example.
| The ones that didn't survive from that point would have
| been called something else.
| titzer wrote:
| Even then, there could have been many breeding pairs of
| humans that were alive and operating and their descendants
| just did not survive until today. As I wrote in my comment,
| it doesn't actually say that the _population_ was 1280
| individuals, just that some 1280 individual _subset_ of the
| population passed on their genetic material to us. The
| descendants of the rest could have died out at any point
| between now and that time.
| daveguy wrote:
| Okay. That's a valid hypothesis. Genetic information from
| only 1280 identified alive during this particular time
| seems evidentiary of a low population during a specific
| time more than something that "just happened". For
| instance, if the 8 billion alive today only propagated
| through 1280 alive sometime in the future you would expect
| a near extinction event to be the cause (we know near
| extinction and extinction aren't particularly rare). Is
| there evidence that it just happened to be 1280 from a
| thriving population of hundreds of thousands or millions?
|
| Edit: otherwise I'm not sure you can claim the hypothesis
| that a near extinction bottleneck is somehow more
| "misleading" than it was something that "just happened" to
| appear like a common event among species. Note -- near
| extinction does not have to be cataclysmic.
| saalweachter wrote:
| It's pretty trivial to fabricate a thought experiment where
| the genetic record looks one way and the historical record
| another.
|
| Let's imagine we've got a thousand islands a million years
| ago, each with a thousand proto-humans living on them.
|
| These islands live in peace and tranquility, with people
| occasionally swimming from one island to another to trade or
| visit or start a new life.
|
| Then one year, one island decides it's had enough of peace
| and tranquility. It cuts off contact with all the other
| islands. From this point on, everyone born on that island is
| a descendant of only the thousand people living on that
| island, instead of intermingling with the neighboring islands
| over time, but there's still a million people.
|
| Then, one generation, they go to war. They swim to a
| neighboring island, kill everyone there, and take it over,
| and then divide themselves between the two islands. The
| population drops from 1 million to 999,000. Over time, they
| expand to fill the two islands, and the population rises back
| to 1 million.
|
| A hundred years later, they decide they need another island,
| so they swim to a third island, kill everyone there, and
| repeat.
|
| Bit by bit, over the course of a hundred thousand years, the
| descendants of the original xenophobic island swim to each of
| the other thousand islands, kill everyone there, and
| repopulate.
|
| In the genetic record, you have a bottleneck -- everyone
| descends from this small starting population. In the historic
| record, you just have a gradual pattern of migration and
| genocide. At no point does the population drop much below the
| original million; at no point does the population of pre-
| humans "almost go extinct".
| borissk wrote:
| IMHO you're only partially correct. The population of our
| ancestors was larger before and after the bottleneck. And it's
| a very important event, no doubt modern human genetics and
| behavior is influenced by it.
| dang wrote:
| (We've replaced the article title with its subtitle, which is
| more specific.)
| asdff wrote:
| The number is also referring to effective population size vs
| the true population size which is larger. For reference the
| effective population size today is estimated to be between
| 10,000-20,000 individuals.
|
| https://bionumbers.hms.harvard.edu/bionumber.aspx?s=n&v=0&id...
| nawgz wrote:
| It's a big claim. To estimate "1280 individuals" is... very
| precise.
| psychphysic wrote:
| The estimate is the estimate (1280 with SEM of 131).
|
| It's be foolish of them to mask it intentionally.
|
| Once independent estimates are made then you might synthesize
| an reasonable estimate.
|
| Both the editor summary I'm science and the headline here don't
| place much emphasis on the precise number.
| adhesive_wombat wrote:
| The actual linked article isn't the paper, and doesn't even
| name the paper as far I can tell, it's just given as "Hu, W.
| et al. Science 381, 979-984 (2023)." in a footnote.
|
| This is the actual paper, which (presumably, I cannot access)
| is specifically about how they made the estimate: _Genomic
| inference of a severe human bottleneck during the Early to
| Middle Pleistocene transition_ :
|
| https://www.science.org/doi/10.1126/science.abq7487
| vic-traill wrote:
| It's obviously the result of Roll Call: SMITH Here! JOHNSON
| Here! WILLIAMS Here! BROWN Here! JONES Here! GARCIA Here!
| MILLER Here! DAVIS Here! RODRIGUEZ Here! MARTINEZ Here!
| HERNANDEZ Here! LOPEZ Here! GONZALEZ Here! WILSON Here!
| ANDERSON Here! THOMAS Here! TAYLOR Here! MOORE Here! JACKSON
| Here! MARTIN Here! LEE Here! PEREZ Here! THOMPSON Here! WHITE
| Here! HARRIS Here! SANCHEZ Here! CLARK Here! RAMIREZ Here!
| LEWIS Here! ROBINSON Here! WALKER Here! YOUNG Here! ALLEN Here!
| KING Here! WRIGHT Here! SCOTT Here! TORRES Here! NGUYEN Here!
| HILL Here! FLORES Here! GREEN Here! ADAMS Here! NELSON Here!
| BAKER Here! HALL Here! [ ... ] ROSADO [ ... Crickets ... ]
| latchkey wrote:
| I upvoted you on the amount of work you put into that
| comment. Even threw in a nguyen there too.
| vic-traill wrote:
| I was shooting for 1280 surnames, but the comment length
| limit fixed that. Which I am grateful for in general :-)
|
| Anyway, I surmised I would give away just about all my
| karma on the comment, but, hell, I just couldn't resist!
| br1 wrote:
| It is a somewhat 'round' number, the width of 720p resolution.
| RoyalHenOil wrote:
| This is the number supported by DNA evidence. There will be a
| margin of error.
|
| The bigger issue, for me, is that I'm not sure how they can
| rule out the possibility that there were lots of other people
| around at that time whose lineages gradually died out. Modern
| genetic lineages may trace back to 1280 people (+/- the margin
| of error), but it seems pretty dubious to assume that those
| were the only people living at that time. It seems highly
| likely to me that there were infertile people, people who died
| young, people whose only living children were infertile or died
| young, etc.
|
| (I did not read the original paper, so maybe they accounted for
| this, or maybe they that specify that this was a genetic bottle
| neck for modern humans, but not necessarily the actual size of
| the population.)
| jltsiren wrote:
| "1280 people" is just a misleading simplification early in
| the linked article. Both the news article and the original
| paper speak of 1280 breeding individuals.
|
| Also, the way population dynamics work, lineages tend to die
| out quickly or not at all. Isolated populations can die out
| gradually, but it takes exceptional circumstances for a
| population to survive in the long term while remaining
| isolated.
| sidfthec wrote:
| > I did not read the original paper, so maybe they accounted
| for this
|
| Then why say it's an issue?
| fooker wrote:
| They haven't.
| postmodest wrote:
| "there were lots of other people around at that time whose
| lineages gradually died out"
|
| It seems to me that if those lineages aren't in the DNA data,
| then they didn't --in the intervening years-- intermix with
| the lineages in the DNA data.
|
| So, ipso facto, those lineages went extinct, and the 1280
| ancestors posited in the study are the non-extinct lineages.
| QED.
| svnt wrote:
| There is a minimum in the fossil record at that time. There
| may be other explanations for it, but one very reasonable one
| is that there just weren't very many skeletons to potentially
| fossilize.
| RoyalHenOil wrote:
| Certainly. However, I am still highly doubtful that there
| were only 1280 people alive at that time. I'm not sure that
| this is what the article is claiming; however, it is
| written in a way that makes it very easy to come away with
| that message (as evidenced in this comment section).
|
| What are the chances that every person alive today, for
| example, will still have living descendants in 400,000
| years? If people 400,000 years in the future do a genetic
| study on themselves to determine how many of their
| ancestors were alive in the year 2023, what percentage of
| the 2023 population will they be able to account for? My
| guess is a fair bit lower than 100%.
| Roboprog wrote:
| Exactly: it's really hard to tell if "the environment" took
| out the other hominids, or if the descendants of the 1280
| took them out.
|
| "Hmm, this monkey looking thing isn't as tasty as a wooly
| mammoth, but it'll do."
|
| (it's not like chimps don't catch and eat other primates)
| spiderice wrote:
| Yeah.. how can they possibly be so precise in that number?
| Anyone know?
| sho_hn wrote:
| They aren't, it's an estimate (with error bars).
| xnx wrote:
| I'm not qualified to say anything about the science, but every
| since reading about the theory described in "When the Sea Saved
| Humanity" (https://www.scientificamerican.com/article/when-the-
| sea-save...), something about the idea of a small band of humans
| holed holding on to survival near the southern tip of Africa has
| captivated me.
| frozenport wrote:
| I'd argue they didn't have too much humanity, or at least what
| differentiates us from Chimpanzees.
| chrisco255 wrote:
| Most certainly they did by then. About 1.8 million years ago
| is when the hand axe (handheld stone axes used as weapons and
| for cutting) was first developed, and fire control was
| developed by 1.5 million years ago by earlier hominids.
| c420 wrote:
| Mastery of fire has entered the chat.
| psychphysic wrote:
| The article suggests control of fire is what lead to recovery
| of the population. So indeed quite a different time.
| ahauxuueei wrote:
| By that time we had mastered fire by probably a million years
| already.
| dontwearitout wrote:
| Thanks for sharing, that was a great read. I've always really
| been fascinated by the aquatic ape hypothesis
| (https://en.wikipedia.org/wiki/Aquatic_ape_hypothesis), even if
| it's not widely accepted as fact.
| autokad wrote:
| I never bought into the aquatic ape theory. besides the fact
| that its not backed up at all by fossil record, we are built
| runners, not swimmers. Furthermore, we are built to be
| vertically oriented, which is horrible for swimming. its one
| of the reasons why humans don't make natural swimmers.
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