5 ms·

Ancient humans, dubbed 'Denisovans', interbred with us

66 points by jamesbritt 16y ago

ecq 16y ago
they're not extinct yet. My extremely annoying and uncivilized neighbor is a Denisovan.
Swizec 16y ago
Perhaps this is being awake for 48 hours straight talking, but this story makes me sad. It is plain as day that when new species emerge, old species breed with one another. Evolution is not a discrete function. Homo Sapiens bred with Homo Neanderthalensis and evidence to support this has existed for a while afaik. What's truly amazing here, but sort of goes hidden in the hype around interbreding (as seen on twitter, this article etc) is that a new species of humans, previously unknown to science, has been discovered. that's the news story, not the boring interbreeding.
- stcredzero 16y ago
  Species and speciation can only be determined historically, anyways.
- hugh3 16y ago
  Surely if they can reliably interbreed with us then they're not another species. Isn't that how "species" is defined? You'll note that the scientists in the article aren't quoted as calling these dudes a "species", they call them a "form". The idea of a "species" isn't terribly well defined over time anyway. Your mother is the same species as you, her mother is the same species as her, and so on. But if you keep following your family tree for far enough you'll start to find things which are clearly a different species from yourself.
  - scott_s 16y ago
    The definition I'm aware of is not actually can they interbreed, but do they do it in practice? From http://www.sciencedaily.com/releases/2005/02/050211082447.htm http://www.sciencedaily.com/releases/2005/02/050211082447.ht...: Members of closely related species possess no physiological differences that would prevent them from interbreeding. But closely related species are distinguished by subtle differences in the pulse rates of male crickets' simple courtship songs, a secondary sexual trait that plays a large role in mate attraction. Among all species of Laupala, pulse rates of male courtship songs range from .5 to 4.2 pulses per second. Female crickets can detect these differences, says Mendelson, and they tend to hop towards the pulse rate of their own species and to reject songs sung at a different tempo. Despite the fact that these crickets can interbreed (and produce fertile offspring, unlike when, say, a female horse and a male donkey produce an infertile mule), we consider them different species because they systematically do not breed. I recall reading about further experiments with similar crickets where scientists manipulated the pulse rates of one cricket species to be the same as the other. Mating occurred.
    - dkarl 16y ago
      I think behavioral and genetic barriers are both considered factors that affect whether crickets "can" interbreed. I'm not sure if scientists would be consistent in applying that standard to humans, though.
  - necolas 16y ago
    There are many different ways to define what constitutes a separate species. The inability to produce viable offspring is just one.
    - dkarl 16y ago
      The difficulties of defining species lead to interesting edge cases, some of which show up in nature, such as ring species: http://en.wikipedia.org/wiki/Ring_species http://en.wikipedia.org/wiki/Ring_species Formally, the issue is that interfertile "able to interbreed" is not a transitive relation – if A can breed with B, and B can breed with C, it does not follow that A can breed with C – and thus does not define an equivalence relation. A ring species is a species that exhibits a counterexample to transitivity.
  - brc 16y ago
    Well a great dane and a chihouha are both the same species - dog. But I wouldn't see them getting it on anytime soon. And yes, you can artificially breed a dane/chihouha hybrid (presuming the resulting pup has a Dane mother?)
- mechanical_fish 16y ago
  Humans, for better and for worse, have a lot of mental machinery dedicated to keeping track of who is sleeping with who, whose child is whose, and whether or not Group X is part of the clan. Any meme which happens to tickle those parts of our minds thereby spreads faster. To a Vulcan, there might be no essential difference between being related to a lizard and being related to your grandmother. To a human, however, the question of whether or not some other creature is your brother-in-law or merely a distant cousin is a very big deal.
  - palish 16y ago
    Could I hire you to follow me around and translate everything everyone is saying to me? Or possibly bribe you.
    - mechanical_fish 16y ago
      If I translate this right, I think you are lobbying for me to become a professional writer. ;) Thanks! I do enjoy the practicing. I'll consider it. Although it's one hell of a career, so I'll either have to think about it pretty carefully, or just accidentally find myself doing it one day without even knowing why.
      - dilap 16y ago
        I just found this reading through your comment history, so +1 from me. :)
- dkarl 16y ago
  It wasn't obvious to me that a population that diverged from ours a million years ago would still be able to interbreed with us less than 50,000 years ago. That's tens of thousands of generations. I'm not surprised that they tried, but mildly surprised that they produced viable offspring. After all, there was previously some doubt that we could have interbred with Neanderthals, and we diverged from them only 500,000 years ago. We're twice as many generations removed from the Denisovans. Or maybe those dates are wrong; the diagram in the article seems to say that the Denisovans and the Neanderthals diverged from the human lineage at the same time. I got the dates I cited from this article from earlier this year: http://news.bbc.co.uk/2/hi/science/nature/8583254.stm http://news.bbc.co.uk/2/hi/science/nature/8583254.stm
  - dkarl 16y ago
    P.S. The other interesting aspect of interbreeding is that it tells us 1) that the humans leaving Africa had significant, repeated encounters with another kind of hominid species, and 2) not only did they interbreed with them, but the offspring were well-enough integrated into early human society that they were able to survive and reproduce further. The second point means that either immediately or eventually, the descendants of the Denisovans were considered fully human. How did that happen? Were the Denisovans already considered fully "human" by the humans leaving Africa? Or were they considered lower, like dogs or cattle? What about vice-versa? The details of the interaction would be fascinating if we could learn them. The interbreeding was doubtlessly often a byproduct of violence, when women were stolen in raids, or when one band wiped out the men of another band in a war and appropriated their land, women, and property. But did it also happen through peaceful means? Were crossbreed children treated as fully "human" right away or were they treated as sub-human until a few more generations of cross-breeding allowed them to "pass?" Were the two kinds of humans similar enough to form families together and feel love and familiar affection, or was it just sheer horndoggery? Could they even learn each other's languages? Interbreeding shows that it makes sense to ask these kinds of questions.
    - ohashi 16y ago
      As fascinating as it would be to know, I doubt we will ever have any conclusive evidence :(
- brc 16y ago
  My understanding was that, based on DNA analysis of Neanderthal remains, humans couldn't successfully interbreed with Neanderthals because of a chromosome mismatch, in the same way a Mule can't get fancy with another mule. So while a Neanderthal/Homo Sapien baby might exist, it was essentially sterile. But I'm happy to be told otherwise, that's just my knowledge as at the last update on the subject, which admittedly was a while ago. Personally I think the 'we all came from Africa' story is a little too neat. I think parallell evolution of Homo Sapiens in separate continents leading to eventual interbreeding is a distinct possibility.
  - zoomzoom 16y ago
    There are probably lots of shades of complexity. Check out "Toba catastrophe theory" for an interesting perspective on "out of Africa".
lucraft 16y ago
Anyone else think: "Battlestar was right!" ? ^^ Also what is the correct punctuation of that sentence??
- CrLf 16y ago
  My first thought... :)
  - deleted 16y ago
    [deleted]
  - meric 16y ago
    What was the above comment talking about?
- ABrandt 16y ago
  I think changing the colon to a comma would do the trick. Anyone else think, "Battlestar was right!"?
  - Quarrelsome 16y ago
    I'm less sure about that, 'cause he's setting up for a quote. That makes the colon correct by my understanding.
    - hugh3 16y ago
      I think it would be correct without any punctuation. Did anyone else think "Battlestar was right"? But we still have to deal with the issue of whether to put the question mark before or after the quote mark. Some folks insist on putting it inside, even when it obviously makes no sense, like in this case.
      - mike-cardwell 16y ago
        The question mark inside quote marks thing has annoyed me for years. I'm sure my English teacher taught me that you should always put it inside the quotation mark, but it doesn't seem logical to me...
stcredzero 16y ago
I'd like to see a more substantive caption on the diagram. I had no idea the French were a branch of early humans. (I take it, it's actually a name for a finding.)
- shin_lao 16y ago
  There are very ancient traces of human groups in France and I suppose that's where the name comes from. Most famous example: http://en.wikipedia.org/wiki/Lascaux http://en.wikipedia.org/wiki/Lascaux
blahedo 16y ago
The tone of the article was a bit strange, as was the way it kept referring to "ancient" genes and such. If they're genes in modern people (Melanesians), how are they any more ancient than any other genes that exist chiefly in one population subgroup? Isn't it becoming increasingly indefensible to talk about "our own" species (or "us") when we know that all these species interbred and that their genetic material lives on in modern humans, even "anatomically modern" humans?
diego_moita 16y ago
If all of this is true, then it is really astonishing. But there's something in this article that sounds very hard to accept: DNA is extremely fragile, it is very hard to imagine it surviving 50 000 years, even in Siberian ice. It is even harder to imagine someone to be able to sequence the entire genome of such species. And also: how can they affirm there's no contamination from human DNA (e.g.: bones remaining from cannibalism)? I'll wait to hear more confirmations of this story.
- mechanical_fish 16y ago
  The article does not say that they sequenced the whole "ancient" genome and indeed it is quite unlikely that they did so. They probably matched lots of isolated segments, however. As for contamination issues... Nothing beats the original article when working out the odds of such a thing.

66 points by jamesbritt 16y ago

ecq 16y ago

they're not extinct yet. My extremely annoying and uncivilized neighbor is a Denisovan.

Perhaps this is being awake for 48 hours straight talking, but this story makes me sad. It is plain as day that when new species emerge, old species breed with one another. Evolution is not a discrete function. Homo Sapiens bred with Homo Neanderthalensis and evidence to support this has existed for a while afaik. What's truly amazing here, but sort of goes hidden in the hype around interbreding (as seen on twitter, this article etc) is that a new species of humans, previously unknown to science, has been discovered. that's the news story, not the boring interbreeding.

stcredzero 16y ago
Species and speciation can only be determined historically, anyways.
hugh3 16y ago
Surely if they can reliably interbreed with us then they're not another species. Isn't that how "species" is defined? You'll note that the scientists in the article aren't quoted as calling these dudes a "species", they call them a "form". The idea of a "species" isn't terribly well defined over time anyway. Your mother is the same species as you, her mother is the same species as her, and so on. But if you keep following your family tree for far enough you'll start to find things which are clearly a different species from yourself.
- scott_s 16y ago
  The definition I'm aware of is not actually can they interbreed, but do they do it in practice? From http://www.sciencedaily.com/releases/2005/02/050211082447.htm http://www.sciencedaily.com/releases/2005/02/050211082447.ht...: Members of closely related species possess no physiological differences that would prevent them from interbreeding. But closely related species are distinguished by subtle differences in the pulse rates of male crickets' simple courtship songs, a secondary sexual trait that plays a large role in mate attraction. Among all species of Laupala, pulse rates of male courtship songs range from .5 to 4.2 pulses per second. Female crickets can detect these differences, says Mendelson, and they tend to hop towards the pulse rate of their own species and to reject songs sung at a different tempo. Despite the fact that these crickets can interbreed (and produce fertile offspring, unlike when, say, a female horse and a male donkey produce an infertile mule), we consider them different species because they systematically do not breed. I recall reading about further experiments with similar crickets where scientists manipulated the pulse rates of one cricket species to be the same as the other. Mating occurred.
  - dkarl 16y ago
    I think behavioral and genetic barriers are both considered factors that affect whether crickets "can" interbreed. I'm not sure if scientists would be consistent in applying that standard to humans, though.
- necolas 16y ago
  There are many different ways to define what constitutes a separate species. The inability to produce viable offspring is just one.
  - dkarl 16y ago
    The difficulties of defining species lead to interesting edge cases, some of which show up in nature, such as ring species: http://en.wikipedia.org/wiki/Ring_species http://en.wikipedia.org/wiki/Ring_species Formally, the issue is that interfertile "able to interbreed" is not a transitive relation – if A can breed with B, and B can breed with C, it does not follow that A can breed with C – and thus does not define an equivalence relation. A ring species is a species that exhibits a counterexample to transitivity.
- brc 16y ago
  Well a great dane and a chihouha are both the same species - dog. But I wouldn't see them getting it on anytime soon. And yes, you can artificially breed a dane/chihouha hybrid (presuming the resulting pup has a Dane mother?)
mechanical_fish 16y ago
Humans, for better and for worse, have a lot of mental machinery dedicated to keeping track of who is sleeping with who, whose child is whose, and whether or not Group X is part of the clan. Any meme which happens to tickle those parts of our minds thereby spreads faster. To a Vulcan, there might be no essential difference between being related to a lizard and being related to your grandmother. To a human, however, the question of whether or not some other creature is your brother-in-law or merely a distant cousin is a very big deal.
- palish 16y ago
  Could I hire you to follow me around and translate everything everyone is saying to me? Or possibly bribe you.
  - mechanical_fish 16y ago
    If I translate this right, I think you are lobbying for me to become a professional writer. ;) Thanks! I do enjoy the practicing. I'll consider it. Although it's one hell of a career, so I'll either have to think about it pretty carefully, or just accidentally find myself doing it one day without even knowing why.
    - dilap 16y ago
      I just found this reading through your comment history, so +1 from me. :)
dkarl 16y ago
It wasn't obvious to me that a population that diverged from ours a million years ago would still be able to interbreed with us less than 50,000 years ago. That's tens of thousands of generations. I'm not surprised that they tried, but mildly surprised that they produced viable offspring. After all, there was previously some doubt that we could have interbred with Neanderthals, and we diverged from them only 500,000 years ago. We're twice as many generations removed from the Denisovans. Or maybe those dates are wrong; the diagram in the article seems to say that the Denisovans and the Neanderthals diverged from the human lineage at the same time. I got the dates I cited from this article from earlier this year: http://news.bbc.co.uk/2/hi/science/nature/8583254.stm http://news.bbc.co.uk/2/hi/science/nature/8583254.stm
- dkarl 16y ago
  P.S. The other interesting aspect of interbreeding is that it tells us 1) that the humans leaving Africa had significant, repeated encounters with another kind of hominid species, and 2) not only did they interbreed with them, but the offspring were well-enough integrated into early human society that they were able to survive and reproduce further. The second point means that either immediately or eventually, the descendants of the Denisovans were considered fully human. How did that happen? Were the Denisovans already considered fully "human" by the humans leaving Africa? Or were they considered lower, like dogs or cattle? What about vice-versa? The details of the interaction would be fascinating if we could learn them. The interbreeding was doubtlessly often a byproduct of violence, when women were stolen in raids, or when one band wiped out the men of another band in a war and appropriated their land, women, and property. But did it also happen through peaceful means? Were crossbreed children treated as fully "human" right away or were they treated as sub-human until a few more generations of cross-breeding allowed them to "pass?" Were the two kinds of humans similar enough to form families together and feel love and familiar affection, or was it just sheer horndoggery? Could they even learn each other's languages? Interbreeding shows that it makes sense to ask these kinds of questions.
  - ohashi 16y ago
    As fascinating as it would be to know, I doubt we will ever have any conclusive evidence :(
brc 16y ago
My understanding was that, based on DNA analysis of Neanderthal remains, humans couldn't successfully interbreed with Neanderthals because of a chromosome mismatch, in the same way a Mule can't get fancy with another mule. So while a Neanderthal/Homo Sapien baby might exist, it was essentially sterile. But I'm happy to be told otherwise, that's just my knowledge as at the last update on the subject, which admittedly was a while ago. Personally I think the 'we all came from Africa' story is a little too neat. I think parallell evolution of Homo Sapiens in separate continents leading to eventual interbreeding is a distinct possibility.
- zoomzoom 16y ago
  There are probably lots of shades of complexity. Check out "Toba catastrophe theory" for an interesting perspective on "out of Africa".

lucraft 16y ago

Anyone else think: "Battlestar was right!" ? ^^ Also what is the correct punctuation of that sentence??

CrLf 16y ago
My first thought... :)
- deleted 16y ago
  [deleted]
- meric 16y ago
  What was the above comment talking about?
ABrandt 16y ago
I think changing the colon to a comma would do the trick. Anyone else think, "Battlestar was right!"?
- Quarrelsome 16y ago
  I'm less sure about that, 'cause he's setting up for a quote. That makes the colon correct by my understanding.
  - hugh3 16y ago
    I think it would be correct without any punctuation. Did anyone else think "Battlestar was right"? But we still have to deal with the issue of whether to put the question mark before or after the quote mark. Some folks insist on putting it inside, even when it obviously makes no sense, like in this case.
    - mike-cardwell 16y ago
      The question mark inside quote marks thing has annoyed me for years. I'm sure my English teacher taught me that you should always put it inside the quotation mark, but it doesn't seem logical to me...

stcredzero 16y ago

I'd like to see a more substantive caption on the diagram. I had no idea the French were a branch of early humans. (I take it, it's actually a name for a finding.)

shin_lao 16y ago
There are very ancient traces of human groups in France and I suppose that's where the name comes from. Most famous example: http://en.wikipedia.org/wiki/Lascaux http://en.wikipedia.org/wiki/Lascaux

blahedo 16y ago

The tone of the article was a bit strange, as was the way it kept referring to "ancient" genes and such. If they're genes in modern people (Melanesians), how are they any more ancient than any other genes that exist chiefly in one population subgroup? Isn't it becoming increasingly indefensible to talk about "our own" species (or "us") when we know that all these species interbred and that their genetic material lives on in modern humans, even "anatomically modern" humans?

diego_moita 16y ago

If all of this is true, then it is really astonishing. But there's something in this article that sounds very hard to accept: DNA is extremely fragile, it is very hard to imagine it surviving 50 000 years, even in Siberian ice. It is even harder to imagine someone to be able to sequence the entire genome of such species. And also: how can they affirm there's no contamination from human DNA (e.g.: bones remaining from cannibalism)? I'll wait to hear more confirmations of this story.

mechanical_fish 16y ago
The article does not say that they sequenced the whole "ancient" genome and indeed it is quite unlikely that they did so. They probably matched lots of isolated segments, however. As for contamination issues... Nothing beats the original article when working out the odds of such a thing.