[HN Gopher] Early humans in Africa may have interbred with an ex...
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Early humans in Africa may have interbred with an extinct species:
new research
Author : diodorus
Score : 79 points
Date : 2020-02-14 06:38 UTC (16 hours ago)
(HTM) web link (theconversation.com)
(TXT) w3m dump (theconversation.com)
| williesleg wrote:
| I love hacker news! So much tech going on here!
| mr_overalls wrote:
| In an intro-level anthropology class I took 20 years ago, we
| learned about the competing models of human evolution:
| Multiregional vs Out of Africa.
|
| Perhaps they dumbed down the complexity for a bunch of freshmen,
| but I remember wondering then why some combination of the two
| wasn't possible.
|
| It certainly looks like a mix of the two canonical models matches
| the data that is being revealed through genetics.
| turtlecloud wrote:
| my suspicion is that the out of Africa theory was promoted
| since it was more PC. Nowadays the "scientific theories" are
| all political.
| TallGuyShort wrote:
| Out of Africa feels less PC to me, but I won't pretend to
| understand the rationale behind what is and isn't considered
| PC a lot of the time. But I agree with GP: we have relatively
| few DNA samples and try to draw pretty big generalizations
| between them. Ituitively, I would expect patterns of
| migration in and out of Africa and all the continents to be
| far more complex than 1-time events from which entire
| populations then developed complete independently.
|
| edit: On a related note, my siblings' DNA test results say
| that they're something like 4% Native American, yet we have
| very reliable documentation of pure British genealogy back on
| all lines almost all the way back to the 1500s. Very unlikely
| to actual have a modern link. I'm sure the companies are
| likely overplaying the similarity more than anthropologists
| would, but am I to conclude that I have a closer link to
| Native Americans than other random samples from Europe?
| cmrdporcupine wrote:
| The DNA tests just look at haplogroups and mtDNA lineages
| etc. to make _very_ broad generalizations about what
| population set some of your ancestors _may_ have belonged
| to.
|
| It's more likely that at some point in the last 15,000
| years someone in your lineage had a child with someone with
| some Siberian background way far back.
| progval wrote:
| > I won't pretend to understand the rationale behind what
| is and isn't considered PC a lot of the time.
|
| It's whatever opinion/theory the person speaking disagrees
| with.
| dominostars wrote:
| The poster clearly said that so that they can stay on
| topic, not sure we need to derail the main conversation
| to air personal grievances.
| cycrutchfield wrote:
| And how exactly is it more PC? Please enlighten us.
| tmn wrote:
| I'm not stating any claim to truth here, but which one
| sounds more pc? Caucasoids diverged from negroids 100k
| years ago. Or, Caucasoids diverged from negroids 2 million
| years ago.
| AlotOfReading wrote:
| You can look at the data yourself, it's not hidden.
|
| Also, the classical meanings of terminology like
| "negroid" or "caucasoid" doesn't really map to genetics.
| My personal experience is that they're almost exclusively
| used by people who aren't familiar with modern
| understandings of human evolution. There are a lot of
| cranks talking about it, so it's often best to avoid
| archaic terminology that might get you mistakenly grouped
| with them.
| ZeroGravitas wrote:
| I think accusing something of being PC implies it's not
| actually correct. So if you're saying one of these is
| more PC, that's a claim that it's less factual. Otherwise
| gravity is PC, 1 + 1 = 2 is PC.
| the_af wrote:
| Neither? It's really hard to understand how one would
| sound more "PC" than the other.
| dhimes wrote:
| Nah, it had nothing to do with PC. Back then, PC was about
| labels: "disabled" (they tried to get "differently enabled"
| to stick!) vs. "handicapped," "little people" vs. "midgets"
| and stuff like that. You were even supposed to say "queer"
| instead of "gay," and some were just starting to use "gender"
| in non-grammatical contexts like referring to a person's
| "gender" (which was look-it-up-in-a-textbook incorrect back
| then).
| AlotOfReading wrote:
| Human evolution is a field that's been evolving very fast
| lately. Even people who graduated only a few years ago are
| wildly out of date if they haven't kept up.
|
| That said, classical multiregionalism is very, very dead and
| has been for awhile. Essentially what you're asking about has
| started to come up lately as a sort of in-Africa
| multiregionalism. This is a nightmare to model mathematically
| and so people just couldn't until recently when new fossils
| made it pretty hard to explain things any other way.
|
| It hasn't fully emerged yet and many people don't really deal
| with it. Take for instance, this paper. One of the fundamental
| assumptions is that there was a singular set (or other time
| limited) of introgression events between archaic and human
| populations. That's a reasonable assumption in older models
| (and dramatically simplifies things), but it's possibly
| violated in an African multiregionalism model.
|
| They claim it's not a problem because of symmetry, a point I'll
| admit I don't fully understand their explanation for in the
| supplementary material.
| s1artibartfast wrote:
| One thing that I always struggle with in these arciles is how the
| percent of common DNA is defined.
|
| >We still think that most - anywhere between about 92% and 98.5%
| - of the ancestry in people not living in Africa today does
| indeed derive from the out-of-Africa expansion.
|
| >Interestingly, they suggest that 6%-7% of the genomes of West
| Africans is archaic in origin. But this archaic ancestry wasn't
| Neanderthal or Denisovan.
|
| How are these numbers reconciled with other statements like 99%
| of the human genome is shared with Bonobos [1]
|
| https://www.sciencemag.org/news/2012/06/bonobos-join-chimps-...
| waserwill wrote:
| Re: definitions of shared DNA:
|
| Some papers will use different definitions, and it can be
| confusing.
|
| Between species (e.g. humans and chimps), it's most often
| considering "non-synonymous mutations," i.e. how many genetic
| differences there are in protein-coding genes (these are
| relevant to structure and function of the protein)
|
| For distant relatives (e.g. humans and bananas), it's similar,
| looking specially at those genes which we can identify across
| many species (particularly those related to cell upkeep, DNA
| replication, structure, etc.).
|
| For within-species, there are a few ways of doing it; you could
| model how much of the genome you expect came from each source
| (as this study did) (see admixture analysis, coalescence), and
| you could look for overall differences on the genome (of all
| existing variation in the species, how much is consistently
| different between populations) (see F-statistics for example)
| s1artibartfast wrote:
| Thank you. This is very helpful!
| danans wrote:
| > How are these numbers reconciled with other statements like
| 99% of the human genome is shared with Bonobos [1]
|
| 99% of any hominid genome - whether Neanderthal, Denisovan, or
| the "archaic" ancestor refererenced - is also shared with
| bonobos. The branching point with bonobos is at a much earlier
| stage of evolution, so all descendant branches have roughly the
| same affinity to them.
| s1artibartfast wrote:
| My point exactly.
|
| How can a homo sapien in Europe share 99% of their genome
| with a Bonobo, but only 92% with another homo sapien in
| Africa
| akiselev wrote:
| 99% is comparing the entire genome, introns and exons. 92%
| is comparing known genes gathered from the human genome
| project and subsequent research. We don't know the exact
| genes expressed by our ancestors since RNA is far less
| likely to survive in enough different types of tissue to
| get a clear picture of the entire genome but 92% of the
| genes we recognize in ourselves can be found in early
| hominids using the latter's full genome sequence. Between
| epigenetics and embryology, we know that the whole
| intron/exon dichotomy is fatally flawed and evolutionary
| genetics has long turned to more complex methods to trace
| relationships, which are very nonlinear even in our near
| family tree.
|
| Both numbers are ridiculous and meaningless so don't pay
| them any mind.
| danans wrote:
| > Both numbers are ridiculous and meaningless so don't
| pay them any mind
|
| I agree that they have little meaning for the purpose of
| individual and group identity. It's been pretty
| disheartening, for example, to see some people
| extrapolate from the discovery of Neanderthal DNA in non-
| African populations to the current economic disparities
| between non-African and African societies. Ironicallly,
| that is a reversal of the previous false stereotypes
| associated with Neanderthal influence in humans. I guess
| once it was proven, it had to be turned into a "good"
| thing.
|
| But the percentages are meaningful for building a picture
| of ancient human evolution and migration.
| nikolay wrote:
| https://phys.org/news/2013-07-chimp-pig-hybrid-humans.html
| TallGuyShort wrote:
| How do we draw the line between species, exactly? Similar to
| this, you can distinguish between races and genders with skeletal
| tendencies now, but we're all one species. So when they are
| compatible enough to bone each other and said boning yields
| offspring, what exactly determines the line between 2 species and
| 2 distinct populations of 1 species?
|
| edit: I'm also always intrigued by statements like this:
| "Interestingly, they suggest that 6%-7% of the genomes of West
| Africans is archaic in origin". I know it's over-simplifying for
| the lay-person, but 6-7% is the high end of what people claim is
| the genetic difference between us and chimpanzees, and we can't
| even reproduce with chimpanzees and don't even have the same
| number of chromosomes. So there's a lot more than that we have in
| common with _some_ archaic species, and a lot less that we 'd
| expect to have with closer relatives.
| angstrom wrote:
| I mean. Donkey+Horse = Mule, but the mule is sterile same with
| Tiger+Lion = Liger. I would assume they were closer relatives
| than that.
| tmn wrote:
| A liger isn't sterile. It does have a lower chance of
| conception though
| yellowapple wrote:
| Technically a mule also has a lower chance of conception.
| fahadkhan wrote:
| Pedantic note:
|
| Female Tiger + Male Lion = Liger.
|
| Male Tiger + Female Lion = Tigon.
| dmos62 wrote:
| Pedantic note:
|
| That's arbitrary patriarchism.
| im3w1l wrote:
| They will have different sex chromosomes (Y from tiger or
| lion) and different mtdna. So there might be some slight
| differences. And it's not out of the question that one is
| more viable than the other.
|
| EDIT: Wikipedia: "Notably, ligers typically grow larger
| than either parent species, unlike tigons"
| dmos62 wrote:
| I'm talking about naming; I'm not saying it doesn't
| matter which is male or female. Why is an offspring of
| lion and tiger called liger? Because the male was lion,
| and vice-versa for tigon. That's just plain patriarchism.
| Is it "bad"? I don't know. We certainly have a tradition
| for it.
|
| Edit: that's a lot of downvotes and no comments. Are we
| beyond talking about sexism, or is my tone so off-
| putting.
| smallnamespace wrote:
| Why do you assume there is a bias in favor of the first
| half?
|
| Does the adjective 'Franco-German' reveal an insidious
| pro-French bias in English?
| mkl wrote:
| You are trying to take an interesting discussion about
| species off on a wildly irrelevant tangent. There is no
| sexism here and the names are not designed to promote
| patriarchy.
| gwd wrote:
| Well obviously _one or the other_ needs to go first. Why
| do you think the first one was chosen because it has the
| greater honor? If it was the other way round, wouldn 't
| it look just as patriarchal to you ("Ladies first" and
| all that)? And are you sure they didn't flip a coin to
| see which parental gender would go first?
| dmos62 wrote:
| I don't know how they made the choice, of course. And if
| you have sexism on your mind, there isn't a right choice
| in this situation, I agree. However, if you take stock of
| all the similar choices (male or female) that we make in
| these mundane contexts, would it come out even? Or would
| it lean heavily to one side?
| Symmetry wrote:
| "Essentially, all models are wrong, but some are useful."
|
| As to the 6% thing that's in the the same sense that you got
| 50% of your genes from your mother. Most of the genes there
| will be identical to the ones your father has on a codon by
| codon basis but their _origin_ is your mother. And by looking
| at the 1% of genes where humans vary from each other we can
| tell which genes came from this ghost population.
| droithomme wrote:
| > when they are compatible enough to bone each other and said
| boning yields _fertile_ offspring
|
| This was a definition of species for a long time. In recent
| years some have advocated for changing it a lot, to the point
| that they should just start calling different dog breeds their
| own species.
|
| Or to go the other way, are dogs and wolves different species?
|
| Is it homo neanderthalensis and homo sapiens or homo sapiens
| neanderthalensis and homo sapiens sapiens?
|
| In my opinion, Denisovans and Neanderthals are both obviously
| types of Homo Sapiens and the argument they aren't is at this
| point mostly promoted by those desperately clinging to the now
| disproven out of africa hypothesis.
| DFHippie wrote:
| > the now disproven out of africa hypothesis.
|
| What? When was it disproven? There's evidence of
| interbreeding outside of Africa with other species, in some
| sense of that word, which also originated in Africa, right?
| Maybe I missed something.
| wnoise wrote:
| The strongest version of "Out of Africa" or "Recent African
| origin of modern humans" is "Modern man developed in
| Africa, and then spread throughout the world, essentially
| unchanged, completely eliminating other archaic hominids".
| Given known interbreeding with other hominids, this is
| clearly false, or at best incomplete to the point of being
| misleading.
|
| This is in contrast to a "Multiregional origin of modern
| humans", which still has "expanding from Africa" first, but
| far before modern man developed, followed by evolution and
| development everywhere without modern features coming from
| Africa "all at once". This too is clearly false and
| misleading. There were large migrations from Africa with
| large genetic distances from the native hominid
| populations, and the resulting mixture appears to be much
| closer to African than the native hominids.
|
| The modern synthesis is multiple waves of expansion out of
| Africa and significant gene flow making the tree look more
| like a river delta: lots of forking but also lots of
| merging, though not to the point of an undifferentiated sea
| either. The exact details are constantly being reevaluated
| as more genetic data is acquired. This is significantly
| different from the strong Out-of-Africa hypothesis, but
| claims there have weakened to include essentially this
| picture. The difference between the two point of views is a
| matter of scale at this point: how strong are the waves out
| of Africa, how much was displacement vs interbreeding, how
| much do genes flow in patterns besides out-from-Africa, how
| much is one giant expansion a reasonable approximation,
| etc.
| ppseafield wrote:
| > So when they are compatible enough to bone each other and
| said boning yields offspring
|
| Apple trees mate readily with pear trees. Most citrus fruits
| are blends of other citrus fruits. Peppermint is a cross breed.
| [0]
|
| And then there's ring species [1], whose members can each mate
| with similar-enough-dna members and produce offspring.
|
| [0] https://en.wikipedia.org/wiki/Peppermint
|
| [1] https://en.wikipedia.org/wiki/Ring_species
| Zenst wrote:
| Alas no hard and fast rule that I'm aware of that fits all
| cases.
|
| It's just a level of difference in which somebody goes, yip
| let's draw a line here and from anything going forwards is a
| new species.
|
| Heck, it certainly isn't defined by having interchangeable
| blood as we all know that don't work with humans.
| solinent wrote:
| I've looked into this, and there's no great way to do so,
| becuase the concept of species really just means large
| morphological changes. We assume everything is taxonomized (a
| tree), but in reality there is no tree--sometimes there is
| cross polination after some time apart. Ultimately they have a
| precise set of morphological criteria for each species, and
| they arrive at this criteria based on a sampling of animals and
| associating their morphology with their DNA.
|
| They also use string similarity algorithms to determine
| morphological order, so we don't strictly know the order at the
| most precise level.
|
| Of course, this is all very controversial, some people think
| we're always changing gradually and some people think we always
| change rapidly. I think they're both wrong--sometimes organisms
| change rapidly, and sometimes they change rapidly, depending on
| environmental factors.
|
| disclaimer: I'm no expert, I've just looked at it from an
| algorithmic view and read some taxonomical texts as I had the
| same question as you.
| iguy wrote:
| The idea of discrete species is just a useful approximation to
| help us think about things. And it's an extremely useful first
| cut, imagine how confusing a farm would be if you didn't
| mentally keep chickens and bulls in different boxes.
|
| But when you look closely enough, there aren't really any such
| exact groupings in nature. Conception only involves the DNA of
| two individuals, not some larger group. And we know that
| species today have common ancestors, and it can't be that there
| was a precise second at which they became distinct, every split
| must have happened gradually.
|
| (Like us, animals also have their own heuristics about other
| animals, including what sort of things they will mate with, but
| it's imperfect. Denim jeans cannot reproduce with poodles, as
| it turns out.)
| golemotron wrote:
| Species is a social construct.
| TheGallopedHigh wrote:
| /s ?
| [deleted]
| [deleted]
| Razengan wrote:
| I've always wondered.. If there ever was another sapient species
| on this planet we either killed them all or interbred with them,
| or they went into hiding.
| kmerrol wrote:
| I'm not sure about extinct. My brother in-law is definitely a
| living example of a new mysterious species of human.
| christiansakai wrote:
| One of why I like HN is that the posts and comments are
| generally serious and comments like these are down-voted.
|
| But nevertheless, I become 2 years old every time I encounter
| comments like this. Thanks for the good laugh.
| magduf wrote:
| Was it a small group of humanoids that came from another star
| system composed of 12 colonies after being pursued by a society
| of artificial lifeforms that was bent on their extermination?
| dghughes wrote:
| Although perhaps the very first life on Earth came across
| extraterrestrial life from a meteor and they interbred?
| DiabloD3 wrote:
| The real question is: was Kara Thrace, at any point, actually
| real?
| dkdbejwi383 wrote:
| So say we all
| staticautomatic wrote:
| No. It had something do with dinosaurs and volcanoes.
| [deleted]
| arel wrote:
| All of this has happened before (probably)
| [deleted]
| [deleted]
| jojostrikesback wrote:
| Definition of species is not clear cut.
| losvedir wrote:
| > _The interbreeding outside Africa happened after our Homo
| sapiens ancestors expanded out of Africa into new environments._
|
| Who's this "our"? Is the author implicitly excluding Africans
| from her audience (or whoever she's talking about), or do I have
| the timeline wrong and the aforementioned interbreeding ancestors
| went _back_ to Africa, and _then_ the "Out of Africa" expansion
| happened?
| IGotThroughIt wrote:
| I don't think this topic can be discussed without people
| getting touchy. Best avoided in my opinion.
| throwaway894345 wrote:
| "our" refers to homo sapiens. Even if she weren't, many (most?)
| Africans probably have ancestors who were not born in Africa at
| some point.
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