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Little known fact: rats, mice and pigs are our closest relatives, beyond primates. Which is why we test stuff on mice. And use pigs in developing medical device

Little known fact: rats, mice and pigs are our closest relatives, beyond primates. Which is why we test stuff on mice. And use pigs in developing medical devices.

thaumasiotes 8y ago
This can't actually be true, because rats and pigs are not closely related to each other. Pigs are more closely related to whales than they are to rats, which means that if (say) we were more closely related to pigs than to rats, we would also be more closely related to whales than to rats. In terms of taxonomy, primates are an order of mammals. It follows immediately that humans are equally closely related to all non-primate mammals. (That's not true either, as you can see by e.g. the designation of marsupials as an "infraclass", a level between class and order, but it's the first approximation to reality.)
- mirimir 8y ago
  I'm sure of it for rodents. Primates and rodents are "supraprimates".[0] Maybe I'm wrong about pigs, though. 0) http://www.els.net/WileyCDA/ElsArticle/refId-a0005306.html http://www.els.net/WileyCDA/ElsArticle/refId-a0005306.html [see Images tab]
- klodolph 8y ago
  You say "that's not true either", but really, it was never true in the first place. Traditional taxonomy is bad at determining how related species are. If you want that, you look for evidences of common ancestors, or do DNA analysis. I tried digging through Wikipedia articles on taxonomy, but it seems to be a bit of a mess, with different articles in the hierarchy using different, incompatible sources. It looks like rodents and primates are both members of clade Euarchontoglires, with common ancestors 85-95 mya. https://en.wikipedia.org/wiki/Euarchontoglires https://en.wikipedia.org/wiki/Euarchontoglires Clade Laurasiatheria is a sibling containing pigs, cats, whales, bats, and many others. Common ancestor with primates is listed as ~80-100 mya (yes, this number doesn't match the other one).
  - thaumasiotes 8y ago
    > Traditional taxonomy is bad at determining how related species are. If you want that, you look for evidences of common ancestors, or do DNA analysis. "Evidence of common ancestors" is precisely what traditional taxonomy looks for. Clades at levels between the traditional taxa were developed by exactly that method. DNA analysis is the same strategy with new technology. > It looks like rodents and primates are both members of clade Euarchontoglires, with common ancestors 85-95 mya. > Clade Laurasiatheria is a sibling containing pigs, cats, whales, bats, and many others. Common ancestor with primates is listed as ~80-100 mya (yes, this number doesn't match the other one). This sure looks like the approximation "primates are equally related to all non-primate mammals" isn't bad...
    - mirimir 8y ago
      > Evidence of common ancestors" is precisely what traditional taxonomy looks for. Clades at levels between the traditional taxa were developed by exactly that method. DNA analysis is the same strategy with new technology. Yes, it's partly based on the fossil record. But the fossil record is very thin. Only a small percentage of stuff gets fossilized. And it's a very subjective approach. There's also morphology and embryology. But those are also very subjective. It's rather like using phrenology in psychiatry and psychology. With molecular generics, we have objective measures for identifying common ancestors and building phylogenetic trees.
      - thaumasiotes 8y ago
        By "evidence of common ancestors", I'm referring to (shared) morphology, not the fossil record.
        mirimir 8y ago
        That's a very weak approach. Or at least, it's very subjective.
  - mirimir 8y ago
    I clearly recall reading that DNA-based phylogenetic analysis indicated that primates and rodents have common ancestors that are more recent than common ancestors with other mammals. So in that sense, rodents are more closely related than, for example, dogs, cats, cattle, etc. Pigs I may be wrong about. They're clearly more similar than dogs, cats and cattle. In embryonic development, for sure, and I remember that from dissecting a fetal pig. And there is the saying that embryology recapitulates phylogeny. But a quick search didn't come up with any DNA-based phylogenetics. As you say, "traditional taxonomy is bad at determining how related species are". It's largely based on morphology, embryology and fossil evidence. But that can be irffy, given the thin fossil record, and the common occurrence of independent selection. DNA-based classification is really the only way to get objective phylogenetic trees. And as we get them, we learn that lots of classical taxonomy is just wrong. And that's why reading about taxonomy online is so confusing. It's a mix of old and new, with lots of more-or-less uninformed speculation.
nkozyra 8y ago
That is not why mice, rats and pigs are used for scientific study, although mice do share about 80% of their dna with humans: https://www.google.com/amp/s/amp.livescience.com/32860-why-do-medical-researchers-use-mice.html https://www.google.com/amp/s/amp.livescience.com/32860-why-d...
- mirimir 8y ago
  Your citation supports my argument: > Another reason rodents are used as models in medical testing is that their genetic, biological and behavior characteristics closely resemble those of humans, and many symptoms of human conditions can be replicated in mice and rats. "Rats and mice are mammals that share many processes with humans and are appropriate for use to answer many research questions," said Jenny Haliski, a representative for the National Institutes of Health (NIH) Office of Laboratory Animal Welfare. That's what you'd expect for for species that share a relatively recent common ancestor. Primates are even closer, of course, but they're much more expensive and problematic to manage.
  - nkozyra 8y ago
    > Your citation supports my argument Part of, but part of it is refuted. Cats and other animals are genetically closer. Rats are preferred not for their genetic similarity, but for similar physiological responses and generic homogeneity.

Little known fact: rats, mice and pigs are our closest relatives, beyond primates. Which is why we test stuff on mice. And use pigs in developing medical devices.

thaumasiotes 8y ago

This can't actually be true, because rats and pigs are not closely related to each other. Pigs are more closely related to whales than they are to rats, which means that if (say) we were more closely related to pigs than to rats, we would also be more closely related to whales than to rats. In terms of taxonomy, primates are an order of mammals. It follows immediately that humans are equally closely related to all non-primate mammals. (That's not true either, as you can see by e.g. the designation of marsupials as an "infraclass", a level between class and order, but it's the first approximation to reality.)

mirimir 8y ago
I'm sure of it for rodents. Primates and rodents are "supraprimates".[0] Maybe I'm wrong about pigs, though. 0) http://www.els.net/WileyCDA/ElsArticle/refId-a0005306.html http://www.els.net/WileyCDA/ElsArticle/refId-a0005306.html [see Images tab]
klodolph 8y ago
You say "that's not true either", but really, it was never true in the first place. Traditional taxonomy is bad at determining how related species are. If you want that, you look for evidences of common ancestors, or do DNA analysis. I tried digging through Wikipedia articles on taxonomy, but it seems to be a bit of a mess, with different articles in the hierarchy using different, incompatible sources. It looks like rodents and primates are both members of clade Euarchontoglires, with common ancestors 85-95 mya. https://en.wikipedia.org/wiki/Euarchontoglires https://en.wikipedia.org/wiki/Euarchontoglires Clade Laurasiatheria is a sibling containing pigs, cats, whales, bats, and many others. Common ancestor with primates is listed as ~80-100 mya (yes, this number doesn't match the other one).
- thaumasiotes 8y ago
  > Traditional taxonomy is bad at determining how related species are. If you want that, you look for evidences of common ancestors, or do DNA analysis. "Evidence of common ancestors" is precisely what traditional taxonomy looks for. Clades at levels between the traditional taxa were developed by exactly that method. DNA analysis is the same strategy with new technology. > It looks like rodents and primates are both members of clade Euarchontoglires, with common ancestors 85-95 mya. > Clade Laurasiatheria is a sibling containing pigs, cats, whales, bats, and many others. Common ancestor with primates is listed as ~80-100 mya (yes, this number doesn't match the other one). This sure looks like the approximation "primates are equally related to all non-primate mammals" isn't bad...
  - mirimir 8y ago
    > Evidence of common ancestors" is precisely what traditional taxonomy looks for. Clades at levels between the traditional taxa were developed by exactly that method. DNA analysis is the same strategy with new technology. Yes, it's partly based on the fossil record. But the fossil record is very thin. Only a small percentage of stuff gets fossilized. And it's a very subjective approach. There's also morphology and embryology. But those are also very subjective. It's rather like using phrenology in psychiatry and psychology. With molecular generics, we have objective measures for identifying common ancestors and building phylogenetic trees.
    - thaumasiotes 8y ago
      By "evidence of common ancestors", I'm referring to (shared) morphology, not the fossil record.
      - mirimir 8y ago
        That's a very weak approach. Or at least, it's very subjective.
- mirimir 8y ago
  I clearly recall reading that DNA-based phylogenetic analysis indicated that primates and rodents have common ancestors that are more recent than common ancestors with other mammals. So in that sense, rodents are more closely related than, for example, dogs, cats, cattle, etc. Pigs I may be wrong about. They're clearly more similar than dogs, cats and cattle. In embryonic development, for sure, and I remember that from dissecting a fetal pig. And there is the saying that embryology recapitulates phylogeny. But a quick search didn't come up with any DNA-based phylogenetics. As you say, "traditional taxonomy is bad at determining how related species are". It's largely based on morphology, embryology and fossil evidence. But that can be irffy, given the thin fossil record, and the common occurrence of independent selection. DNA-based classification is really the only way to get objective phylogenetic trees. And as we get them, we learn that lots of classical taxonomy is just wrong. And that's why reading about taxonomy online is so confusing. It's a mix of old and new, with lots of more-or-less uninformed speculation.

nkozyra 8y ago

That is not why mice, rats and pigs are used for scientific study, although mice do share about 80% of their dna with humans: https://www.google.com/amp/s/amp.livescience.com/32860-why-do-medical-researchers-use-mice.html https://www.google.com/amp/s/amp.livescience.com/32860-why-d...

mirimir 8y ago
Your citation supports my argument: > Another reason rodents are used as models in medical testing is that their genetic, biological and behavior characteristics closely resemble those of humans, and many symptoms of human conditions can be replicated in mice and rats. "Rats and mice are mammals that share many processes with humans and are appropriate for use to answer many research questions," said Jenny Haliski, a representative for the National Institutes of Health (NIH) Office of Laboratory Animal Welfare. That's what you'd expect for for species that share a relatively recent common ancestor. Primates are even closer, of course, but they're much more expensive and problematic to manage.
- nkozyra 8y ago
  > Your citation supports my argument Part of, but part of it is refuted. Cats and other animals are genetically closer. Rats are preferred not for their genetic similarity, but for similar physiological responses and generic homogeneity.