Arnie is a very happy dog (see photo in upper left). Its always a party when Arnie is around– He loves everyone and everything…

… Everything, that is, except cats.

It didnt used to be like that. Arnie used to like cats just fine. But then one day, when he was a puppy…

Neighbor: Hey can I introduce my new kitten to Arnie? I want to get a dog later, so I want her to be used to dogs.
Me: Sure!

Arnie: *happyhappyhappynewfriendhappyhappy*
Kitten: *squint*
Arnie: *newfriendnewfriendsofluffyhappyhappyhappy*
Kitten: *squint*
Arnie: *haaaaaaappyhappyhappy…
Arnie: *fightsbackpuppytears*… NOMNOMNOMNOM!!!!!! NOMNOMNOMNOM!!!!!!

Aaaaaand now whenever Arnie sees a cat, he goes full on ‘NOMNOM’.


Im not looking forward to breaking this news to him– Incontrovertible proof that cats and dogs shared a common ancestor 60-85 million years ago:

From the Cover: Ancestral capture of syncytin-Car1, a fusogenic endogenous retroviral envelope gene involved in placentation and conserved in Carnivora.

There is a protein necessary for the formation of placentas in mammals, syncytin. Syncytin is a retroviral protein, envelope, that has been coopted for the hosts purposes from endogenous retroviruses. This didnt happen just once, at the origin of mammals– It might have happened then, but then as different species evolved, they selected different ERV Envs that worked ‘best’ for them, meaning that different mammals use different ERV Envs for the same purpose. Simians have syncytin-1 and syncytin-2. Mice have syncytin-A and syncytin-B. A species of rabbit has syncytin-Ory1.

As these authors indicate, domesticating retroviral genes for other purposes isnt rocket science:

… on several occasions in the course of mammalian evolution, env genes from endogenous retroviruses have been co-opted by their host to participate in the formation of the placenta.

Interestingly, this stochastic acquisition of genes of exogenous origin might be related to the unexpectedly large diversity observed in placental structures and the physiology of placentation among eutherian mammals.

When the dog (Canis lupus familiaris) and cat (Felis catus) genomes were sequenced, they identified several envelope genes that *might* be playing the syncytin role in these organisms. They then looked for mRNA from these genes in dog and cat placenta, indicating which of the genes was actually active in that location.

They found a hit, which they named syncytin-Car1. ‘Car‘ because that envelope gene is found in orthologous genomic locations in 26 species of carnivores (including Giant Pandas!)– nestled inside of an intron of some GTPase gene (TBC1D19):

Moreover, high sequence homology of the sequences flanking the proviruses (pairwise percentage of identity comprised between 78% and 82% over 1 kb of the 5′ flanking region and between 59% and 67% over 1 kb of the 3′ flanking region for the three proviruses) as well as the presence of a SUMO-like pseudogene inserted at the same position within all three proviruses (Fig. 6B) confirm that they are strict orthologous copies of the same gene in the dog, cat, and giant panda genomes.

Common descent FTW!!

But poor, poor Arnie…


  1. #1 Rokujolady
    February 20, 2012

    Did arnie eat the neighbor’s kitten, because I can’t feel bad for him if he did.

  2. #2 ERV
    February 20, 2012

    LOL, no, did not get to carry out the ‘NOM’. He just wanted to REALLY BADLY.


  3. #3 Justicar
    February 20, 2012

    Telling Arnie that cats and dogs share a common ancestor and that he should therefore be nice to cats is, in this case, quite literally the genetic fallacy!

  4. #4 Tezcatlipoca
    February 20, 2012

    Does Coyne know about this!!! Ceiling Cat sez Hairetick!!!

  5. #5 EvilYeti
    February 20, 2012

    abbie smith iz graduate student studyin molecular n biochemical evolution uv hiv within patient n within populationz. she also studiez epigenetic control uv ervz.

  6. #6 Steve
    February 20, 2012

    When you consider that Cats are gods, while Dogs are dyslexic, then throw in the fact that they’re related, you end up with a religious/fratricidal feud that goes off like the Hatfields and McCoys with nuclear weapons.

  7. #7 HalfMooner
    February 21, 2012

    Hi, Abbie!

    Poor Arnie, indeed. Like Richard Dawkins, he’s now being held to blame for the what his distant ancestors were? Unfair!

  8. #8 Ewan R
    February 21, 2012

    Coolest shit I’ve seen all day.

    I did not know the evolutionary underpinnings of the placenta.

    Nerdiness +1.


  9. #9 hoary puccoon
    February 21, 2012

    So Paul Nelson, YEC, Discovery Institute fellow, and author of, “Of Pandas and People,” sort of had a point in focusing on the placenta in a “gee, how could that ever have evolved without a Designer?” way. Because, apparently, placentas didn’t evolve through normal genetic mutations.

    But, now we know. Evolution took a different– but equally natural– route in the evolution of placentas. So, either there is no Designer, or the Designer is an endogenous retrovirus– which would seem to be an underqualified choice to fill the position of Supreme Ruler of the Universe.

    But leaving that aside, if Nelson were a real scientist and had he been really puzzled by the development of the placenta, he would now be shooting off emails to the authors of this study saying “thank you, thank you, thank you, this has puzzled me for years;” making statements to the press about This is a Major Breakthrough; and writing his own grant proposals to get in on the next round of experiments.

    If he were a real scientist, that is. What he will actually do is keep shilling for the Disco Institute as if this study had never happened.

  10. #10 kad
    February 22, 2012

    Hey Arnie,sharing a 60 million year old common ancestor with a cat isn’t nearly as repulsive is sharing much more recent common ancestry with Rick Santorum, so suck it up, dude.

  11. #11 Catalac
    February 22, 2012

    It’s all a fundamental cultural difference you see. Cats just don’t “get” dog excitement. To them it seems confrontational or at least very rude to be jumping all around “excited” like that. Generally, cats prefer to size someone up at a distance and slowly get closer.

    Personally, I’m more like a cat than a dog. I can’t stand those who try to work in a “hug” on a first meeting. Heck, for that matter I don’t find the dog’s excitement all that deliteful myself. I’m not saying dogs are bad, just that their whole system of greeting doesn’t mesh well with most cats, and some humans.

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