4 ms·

They aren't. They are Homo sapiens, vs homo neanderthalis, homo erectus or the like. There used to be many closely related humans. But we eradicated them (in al

by ricw 9y ago

They aren't. They are Homo sapiens, vs homo neanderthalis, homo erectus or the like. There used to be many closely related humans. But we eradicated them (in all likelihood). From that perspective, sapiens would be a better term than humans..

danieltillett 9y ago
We haven't eradicated them, we have bred with them. Most of us are the decendents of both the sub-Saharan people and Neanderthal people and some of us are the descendants of sub-Saharan people, Neanderthal people, and the Denosovan people (three different species). If we are all human now then why is only one ancient population from Africa called human.
- gwern 9y ago
  We bred with them, but evolution has been heavily eliminating the traces of the breeding and they are generally often linked with diseases. So they do not seem to be on equal grounds. And as for 'us' - speak for yourself, but much of the human race has no Denisovan or Neanderthal ancestry.
  - wyck 9y ago
    Unless you are secretly Ozzy Osbourne, something I always suspected, https://www.scientificamerican.com/article/ozzy-osbourne-genome/ https://www.scientificamerican.com/article/ozzy-osbourne-gen...
  - Mikeb85 9y ago
    > much of the human race has no Denisovan or Neanderthal ancestry. But most does. Any population originally of Asian or European descent has some Denisovan or Neanderthal DNA, or ~80 percent of the world's population.
    - gwern 9y ago
      A fifth of the entirety of humanity is a heck of a lot. If you want to claim that Denisovan or Neanderthal ancestry is just as crucial as the basal homo sapiens, you are writing off a good chunk of humanity. Combine this with the purging of Neanderthal DNA (and the likely purging of the little bit of Denisovan introgression), it's clear that one of these things is not like the others. Let's not overstate the implications of these things.
  - rlpb 9y ago
    > ...but evolution has been heavily eliminating the traces of the breeding and they are generally often linked with diseases. Do you have a citation for this? I was under the impression that greater genetic diversity usually leads to greater disease resistance, because disease-prone genes tend to be eliminated more quickly by natural selection.
    - gwern 9y ago
      Sure. Here's some relevant ones: "The phenotypic legacy of admixture between modern humans and Neandertals" https://www.gwern.net/docs/genetics/2016-simonti.pdf https://www.gwern.net/docs/genetics/2016-simonti.pdf , Simonti et al 2016; "The Genetic Cost of Neanderthal Introgression" http://www.genetics.org/content/203/2/881 http://www.genetics.org/content/203/2/881 , Harris & Nielsen 2016; "The Strength of Selection against Neanderthal Introgression", Juric et al 2016 http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1006340 http://journals.plos.org/plosgenetics/article?id=10.1371/jou... https://www.nytimes.com/2016/11/09/science/neanderthal-dna-natural-selection.html https://www.nytimes.com/2016/11/09/science/neanderthal-dna-n... . Not all of the work has been published yet; Razib Khan has been tweeting some recent posters/presentations on more work on Neanderthal purging and uneven inheritance suggesting that the Neanderthal variants were especially harmful for some things like the central nervous system ( https://twitter.com/jgschraiber/status/881995470515687425 https://twitter.com/jgschraiber/status/881995470515687425 https://twitter.com/StoneLab_ASU/status/881994861158813697 https://twitter.com/StoneLab_ASU/status/881994861158813697 https://twitter.com/jgschraiber/status/881995155875692544 https://twitter.com/jgschraiber/status/881995155875692544 https://twitter.com/jgschraiber/status/881994429510365186 https://twitter.com/jgschraiber/status/881994429510365186 https://twitter.com/jgschraiber/status/881993396642091009 https://twitter.com/jgschraiber/status/881993396642091009 ). Greater genetic diversity might seem like a good thing, but there's a lot of details. Neanderthals might have been too alien for their variants to be 'compatible' with humans (not as surprising as it might sound, an interesting paper from yesterday reports that this sort of incompatibility may be responsible for as many as 95% of one project's mouse strains dying out despite all of them being interbreedable: http://genestogenomes.org/behind-the-cover-male-infertility-in-the-mouse-collaborative-cross/ http://genestogenomes.org/behind-the-cover-male-infertility-... ), or they may have suffered from a higher mutation load due to their small population - small populations can't select as effectively against bad mutations, so will be genetically less healthy. (This also might be part of why human mutation load was shrinking over time up until a few thousand years ago, "The Genomic Health Of Ancient Hominins" http://biorxiv.org/content/early/2017/06/02/145193 http://biorxiv.org/content/early/2017/06/02/145193 Berens et al 2017, all the new variants being slowly sorted through.) Thus, while some Neanderthal/Denisovan variants may have been helpful to humans (like the Tibetan altitude adaptations), overall they appear to have been harmful and are disappearing.
delecti 9y ago
I often see Neanderthals referred to as Homo sapiens neanderthalensis, so it's not quite as clear cut that they're a separate species. And indeed, by the definition of "a population that can interbreed and produce viable offspring", if many of us have Neanderthal genes then we would be the same species.

by ricw 9y ago

danieltillett 9y ago

We haven't eradicated them, we have bred with them. Most of us are the decendents of both the sub-Saharan people and Neanderthal people and some of us are the descendants of sub-Saharan people, Neanderthal people, and the Denosovan people (three different species). If we are all human now then why is only one ancient population from Africa called human.

gwern 9y ago
We bred with them, but evolution has been heavily eliminating the traces of the breeding and they are generally often linked with diseases. So they do not seem to be on equal grounds. And as for 'us' - speak for yourself, but much of the human race has no Denisovan or Neanderthal ancestry.
- wyck 9y ago
  Unless you are secretly Ozzy Osbourne, something I always suspected, https://www.scientificamerican.com/article/ozzy-osbourne-genome/ https://www.scientificamerican.com/article/ozzy-osbourne-gen...
- Mikeb85 9y ago
  > much of the human race has no Denisovan or Neanderthal ancestry. But most does. Any population originally of Asian or European descent has some Denisovan or Neanderthal DNA, or ~80 percent of the world's population.
  - gwern 9y ago
    A fifth of the entirety of humanity is a heck of a lot. If you want to claim that Denisovan or Neanderthal ancestry is just as crucial as the basal homo sapiens, you are writing off a good chunk of humanity. Combine this with the purging of Neanderthal DNA (and the likely purging of the little bit of Denisovan introgression), it's clear that one of these things is not like the others. Let's not overstate the implications of these things.
- rlpb 9y ago
  > ...but evolution has been heavily eliminating the traces of the breeding and they are generally often linked with diseases. Do you have a citation for this? I was under the impression that greater genetic diversity usually leads to greater disease resistance, because disease-prone genes tend to be eliminated more quickly by natural selection.
  - gwern 9y ago
    Sure. Here's some relevant ones: "The phenotypic legacy of admixture between modern humans and Neandertals" https://www.gwern.net/docs/genetics/2016-simonti.pdf https://www.gwern.net/docs/genetics/2016-simonti.pdf , Simonti et al 2016; "The Genetic Cost of Neanderthal Introgression" http://www.genetics.org/content/203/2/881 http://www.genetics.org/content/203/2/881 , Harris & Nielsen 2016; "The Strength of Selection against Neanderthal Introgression", Juric et al 2016 http://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1006340 http://journals.plos.org/plosgenetics/article?id=10.1371/jou... https://www.nytimes.com/2016/11/09/science/neanderthal-dna-natural-selection.html https://www.nytimes.com/2016/11/09/science/neanderthal-dna-n... . Not all of the work has been published yet; Razib Khan has been tweeting some recent posters/presentations on more work on Neanderthal purging and uneven inheritance suggesting that the Neanderthal variants were especially harmful for some things like the central nervous system ( https://twitter.com/jgschraiber/status/881995470515687425 https://twitter.com/jgschraiber/status/881995470515687425 https://twitter.com/StoneLab_ASU/status/881994861158813697 https://twitter.com/StoneLab_ASU/status/881994861158813697 https://twitter.com/jgschraiber/status/881995155875692544 https://twitter.com/jgschraiber/status/881995155875692544 https://twitter.com/jgschraiber/status/881994429510365186 https://twitter.com/jgschraiber/status/881994429510365186 https://twitter.com/jgschraiber/status/881993396642091009 https://twitter.com/jgschraiber/status/881993396642091009 ). Greater genetic diversity might seem like a good thing, but there's a lot of details. Neanderthals might have been too alien for their variants to be 'compatible' with humans (not as surprising as it might sound, an interesting paper from yesterday reports that this sort of incompatibility may be responsible for as many as 95% of one project's mouse strains dying out despite all of them being interbreedable: http://genestogenomes.org/behind-the-cover-male-infertility-in-the-mouse-collaborative-cross/ http://genestogenomes.org/behind-the-cover-male-infertility-... ), or they may have suffered from a higher mutation load due to their small population - small populations can't select as effectively against bad mutations, so will be genetically less healthy. (This also might be part of why human mutation load was shrinking over time up until a few thousand years ago, "The Genomic Health Of Ancient Hominins" http://biorxiv.org/content/early/2017/06/02/145193 http://biorxiv.org/content/early/2017/06/02/145193 Berens et al 2017, all the new variants being slowly sorted through.) Thus, while some Neanderthal/Denisovan variants may have been helpful to humans (like the Tibetan altitude adaptations), overall they appear to have been harmful and are disappearing.

delecti 9y ago

I often see Neanderthals referred to as Homo sapiens neanderthalensis, so it's not quite as clear cut that they're a separate species. And indeed, by the definition of "a population that can interbreed and produce viable offspring", if many of us have Neanderthal genes then we would be the same species.