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Early humans in Africa may have interbred with an extinct species: new research (theconversation.com)
116 points by diodorus 14 days ago | hide | past | web | favorite | 102 comments



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.


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.)


> 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


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.


The further you zoom out, the more tree-like it gets, but if you zoom in on any particular node in the tree, like hominids, then it becomes a tangled mess.


Exactly.

It's my vague impression that you get species that can't interbreed after extended geographic/habitat isolation. But short of that, it's a tangled mess, with complex fertility patterns.


I remember learning this vaguely as well, it's just a relatively useful rule with lots of exceptions, but it is not a law--it happens even after extended isolation: https://en.wikipedia.org/wiki/Hybrid_(biology)

https://en.wikipedia.org/wiki/Interbreeding_between_archaic_...

Some examples of hybrids without human influence (well that's arguable):

https://en.wikipedia.org/wiki/Lonicera_fly

https://en.wikipedia.org/wiki/Red_wolf

The grand daddy of "hybrids" (twelve species):

https://en.wikipedia.org/wiki/Celosia_argentea

from here: https://en.wikipedia.org/wiki/Hybrid_(biology)#Speciation

Also you can go beyond hybrids: https://en.wikipedia.org/wiki/Polyploidy#Types

As an amateur I'd hypothesize if the species diverges and then relocates, but is subject to similar environmental pressure, the morphological changes won't be great enough to prevent the organisms from interfacing and then reproducing.

We've determined this through string similarity algorithms, so really I'd say we can't be completely certain here either.


Thanks! Lots of great links there.

"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.


>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?

You can't. In practice, extinct branches of humans are classified as separate species, and animals are classified as a bunch of species because biologists get credit for discovering new species. In contrast, living branches of humans (e.g. bushmen vs. pygmies vs. everyone else) ar classified as a single species even if they have evolved largely in isolation for hundreds of thousands of years and rarely interbreed, because classifying them separately could give ammo to racists and worse.

>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.

It usually means 6-7% of genes that vary between humans.


> In practice, extinct branches of humans are classified as separate species

They were classified that way, until the presence of Neanderthal & Denisovan DNA was discovered in modern humans.

> In contrast, living branches of humans (e.g. bushmen vs. pygmies vs. everyone else) ar classified as a single species even if they have evolved largely in isolation for hundreds of thousands of years and rarely interbreed

They are classified as a single species with the rest of humans because they can interbreed with other humans, not for political reasons.

We couldn't draw the same conclusion about extinct branches until recently because we don't have living groups of them that we can observe interbreeding. Now that we see the genetic evidence of that the classification has changed.


> They are classified as a single species with the rest of humans because they can interbreed with other humans

This is not the standard for, e.g. birds, however. Consider the mallard. It's happy to breed (with fertile offspring) with just about any duck. However the ornithology community does not say "great, they're all ducks, maybe with separate subspecies". Instead they complain about "genetic pollution" wiping out species of ducks through genetic drift.

Myself, I think it would be perfectly reasonable to call these subspecies and keep the Biological Species Concept[1], but in actual usage the Biological Species concept is dead.

[1] https://en.wikipedia.org/wiki/Species_concept#Mayr.27s_Biolo...


In the past the rules for 'species' was not whether or not they will interbreed, but whether or not their offspring would be fertile.

A horse and a donkey can breed just fine, but a mule cannot.

This makes sense because we know that species eventually differentiate and whether or not they can recombine is a good indication of how far apart that separation is.

But nowadays all that stuff is thrown out of the window. I don't really understand why it is no longer considered a useful distinction.


> A mule cannot [breed].

That's almost always true, but isn't an absolute. There are documented cases of fertile mare mules: https://en.wikipedia.org/wiki/Mule#Fertility


The Hawaiian duck isn't racist enough in choosing mates so now conservationists want to bring back more genetically pure Hawaiian ducks through selective breeding. It's rather ridiculous.


>They are classified as a single species with the rest of humans because they can interbreed with other humans

https://en.wikipedia.org/wiki/List_of_genetic_hybrids


First, many organisms reproduce asexually and are thus classified into species on other grounds. Second, animals that have the ability to produce fertile offspring with each other are still often classified as separate species or at least subspecies (depending on whose definition you use) if they don't customarily interbreed and have differing appearances / characteristics.


Are lions and tigers different species?


Male ligers are sterile, so it's more plausible to call the parents different species.

I've seen no evidence to support the proposition that the children of San and Pygmies with outside human populations are sterile.

Given that, the question is what would the motivation possibly be to call them a separate species from the rest of humanity?


There is evidence that the male offspring of the Neanderthal/African Homo spp. were infertile.


Even if that were true, what does that have to do with the Pygmies or the San?


Nothing as Pygmies and the San are not different species of the homo genus.

> 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

Those percentages aren't measuring the same thing. Chimp to human is a total genome comparison. Human to Hominid ancestor X is based on identified humane genes. The latter is a tiny subset of the former.


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.


I mean. Donkey+Horse = Mule, but the mule is sterile same with Tiger+Lion = Liger. I would assume they were closer relatives than that.


A liger isn't sterile. It does have a lower chance of conception though


Technically a mule also has a lower chance of conception.


Pedantic note:

Female Tiger + Male Lion = Liger.

Male Tiger + Female Lion = Tigon.


[flagged]


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"


[flagged]


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.


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?


It's off topic and inflammatory. And this follow up comment reinforces the appearance that the point is basically shit stirring and nothing else.

I talk about sexism pretty regularly on HN. Sometimes it doesn't go well and sometimes it does. You absolutely can discuss sexism here. This is just not a good approach to doing so.


Yes, that’s arbitrary; unless we decide to always make the sexes explicit, we have to make a choice as to whether to mention the male parent or the female parent first.

Hoever, just as with Liger and Tigon, the two donkey/mule variants have different names:

Male Donkey (jack) + Female Horse (mare) = Mule

Female Donkey (jenny) + Male Horse (stallion) = Hinny

Hinnies are rarer, but do exist (https://en.wikipedia.org/wiki/Hinny)


Clever. They finessed it by inventing new names, rather than combining parts of the parent species.


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?


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?


How do we draw the line between species, exactly?

As others here have noted, it's generally or historically been deemed to be a pairing expected to produce a fertile offspring that can interbreed with others of the same group.

Though, really, DNA is just two RNA. We are made up of the same code that makes bacteria and even viruses. So it's bound to be messy and highly hackable.

https://www.iflscience.com/health-and-medicine/ancient-virus...

I can't readily find a really good article about the (controversial) theory that humans descended from a pig-chimp mating, but you can Google it.


I found an article written in 2013 and it was an interesting read. But it seems the author was not aware that domestication also leads to a change in physical appearances in every animal we know thus maybe cause and effect are reversed?

In a recent episode of the Grand Tour locals from Colombia were proud to fuck their donkey so I didn't want to dismiss this hypothesis on forehand.

https://www.google.com/amp/s/www.dailymail.co.uk/sciencetech...


There are not sharp lines, just fuzzy boundaries.

We do have to discuss and reason about living creatures with other humans though, so it's helpful to name and categorize, just know that the names and categories are a human language construct, nothing more.


Just because you can define a group, doesn't mean that's inherently divisive. Like you mentioned, species are approximately defined by their ability to mate and produce offspring, as part of a larger taxonomical hierarchy but certainly not exhaustive on its own.


Jay Gould and the Ant Ecologist have the best info on that.Eo Wilson his college book for ecology classes.

> 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.


> 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.


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.


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-...


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)


Thank you. This is very helpful!


> 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.


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


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.


> 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.


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?


My first thought was this book series that speculated on time-traveling humans interbreeding with aliens with a take on the mythology of elves and dwarves.

https://en.wikipedia.org/wiki/Saga_of_Pliocene_Exile


The real question is: was Kara Thrace, at any point, actually real?


Of course she was real. She had a mother, history and upbringing. Now as to whether the post-death Thrace ( "the second coming" ) was the "spirit/angel" of Thrace or an altogether different entity separate from Thrace ( like physical Gaius and the "spiritual/angelic/head" Gaius you see at the end of the series ) that's up for debate.

Her destiny ( teased throughout the series ) was to sacrifice herself to lead humanity to salvation ( earth ). It's similar to Christ in a way - self-sacrifice and the second coming to lead the faithful to the kingdom of god.


I've watched through BSG I think 3 times over the years, and I've come to the conclusion that I don't think she was strictly human, in the normal sense.

I think from day one of her existence, she was a kind of power on the same level as Baltar and Six's angelic alter egos. Watching it the first time when it originally aired, I had thought she was one of the Five (even though part of me thought that was too obvious, and a cop out)... and then the fifth member was revealed and it wasn't her.

Clearly the writers had given her a role beyond merely human or Cylon, something part of the grand scheme of God that Messenger/Head Baltar and Six were part of.


Ignore the last episode and the show is much saner.

So say we all


Although perhaps the very first life on Earth came across extraterrestrial life from a meteor and they interbred?


No. It had something do with dinosaurs and volcanoes.


All of this has happened before (probably)



I love this theory. Not because I believe it, but because of how entrancingly bold it is. I sometimes wonder what we believe in that future generations will look down upon us for. Surely we haven’t discovered everything, right? Surely there are some things we think we know that is actually completely wrong.

Is it that human origins are rooted in chimp-pig hybridization? Probably not, but it is high on my “just might be crazy enough to be right” list. The odd similarity-dissimilarities among human, pig, and primate are just too interesting to be dismissed out of hand.


Exactly my point as well - science shouldn't shy away from stuff we wouldn't like. That's why I also respect Copernicus, Darwin, and Freud so much - they dared to tell us things we didn't like, but they didn't care much; they only cared about the scientific truth.


It's not accidental that young biologists dissect fetal pigs.


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.


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.


my suspicion is that the out of Africa theory was promoted since it was more PC. Nowadays the "scientific theories" are all political.


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).


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?


> 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.


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.


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.


What if one of your ancestors cheated on their spouse? Isn't that possible?


There weren't a lot of Native Americans emigrating to the British Isles pre-1800, east India, or Zambia, but sure anything's possible.


And how exactly is it more PC? Please enlighten us.


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.


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.


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.


Neither? It's really hard to understand how one would sound more "PC" than the other.


I can't imagine how stupid I would have to be to not comprehend this statement.


Species is a social construct.


/s ?


Absolutely not. There's no clear, ambiguous definition of "species" that does not have counter-intuitive implications. No, the classic "fertile over two generation" thing you learn in high school doesn't cut it. Also, the commonly used criterion vary from which domain is being dealt with.

In practice, this means that two individuals are said to belong to a different (resp. identical) species if everyone in the community agrees that they do. That's what it means to be a "social construct", not that the differences per se aren't real.

Justifying other statements on the lines of "X is a social construct" similarly, where X ranges across a variety of more-or-less controversial concepts, is left as an exercise to the reader.


you start to realize that the color blue is a social construct if you are willing to abandon all reason.


Except the color blue is at least partially a social construct[0].

[0]https://tvtropes.org/pmwiki/pmwiki.php/UsefulNotes/GreenIsBl...


Does that make the colour blue a social construct, or the word blue a social construct?

After all, #0000ff is #0000ff no matter what you call it or through whose eyes it reflect photons. ;)


#0000ff doesn't exist in nature. Human beings don't see color directly in hexadecimal values - indeed, additive color (RGB) as broadcast from a monitor and subtractive color as exists in nature are physically different processes. Rather, the perception of color is subjective and error prone (see a HN subthread on the color brown[0,1] or other examples of color illusions like the viral dress from a few years ago, or the red-grey illusion[2].

Blue is a social construct because what "blue" means is taught to us by the culture around us, and different cultures classify colors differently[3,4]. If one culture considers blue and green to be the same color, and another considers them distinct, that's not merely a disagreement over taxonomy, but concept.

[0]https://news.ycombinator.com/item?id=22324298

[1]https://news.ycombinator.com/reply?id=22326975&goto=item%3Fi...

[2]https://www.vice.com/en_us/article/wnkq5n/this-picture-has-n...

[3]https://en.wikipedia.org/wiki/Blue%E2%80%93green_distinction...

[4]https://en.wikipedia.org/wiki/Linguistic_relativity_and_the_...


[flagged]


"pure biology" is a human field of study, and is full of corner cases where different people disagree about the exact definition/distinction of individual species. I.e. many sub-fields have 2-3 standard reference books that do not 100% agree on which species exist, and where they do it often is "we've agreed to define it as this" (and then sometimes someone finds a new population inbetween or runs DNA tests and the whole debate kicks off again). Do you disagree with that, or do you merely object to calling that "social construct", and why?


I tried explaining that to the judge ...


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.


Or they died out long before we appeared:

https://en.wikipedia.org/wiki/Silurian_hypothesis


Not mentioned in that Wikipedia article, but the explanation for "why is there no ancient plastic around" is that the civilization could have pre-dated oil. Not enough time may have passed for significant amounts of the stuff to accumulate in the planet, so the civilization would have never developed a use for it. It would have been a rarity to them, not a foundational cornerstone of civilization.

It's a cool thought experiment, but also very cool to think about how much we lucked out not just to be on Earth, but to be on Earth at this point in time. Emerge a bit earlier and suddenly industrialization becomes exponentially harder.


And an Earth with ... a lot of handy animals and such!


> 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?


As a black person of African descent, I feel confident in saying that the group called homo sapiens, of which I and all of my ancestors for millennia am a part, expanded out of Africa into new environments.


"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.


I don't think this topic can be discussed without people getting touchy. Best avoided in my opinion.


Definition of species is not clear cut.


I'm not sure about extinct. My brother in-law is definitely a living example of a new mysterious species of human.


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.


I love hacker news! So much tech going on here!




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