Sunday, November 03, 2013

How Many Different Cell Types in an Adult Human?

We're having a little discussion about complexity in the comments from my post of last Friday [Vertebrate Complexity Is Explained by the Evolution of Long-Range Interactions that Regulate Transcription?]. I pointed out that many scientists just can't come to grips with the idea that humans aren't much more complicated than other animals. We are not special. I call this The Deflated Ego Problem.

One of the minor arguments in favor of human exceptionalism is the idea that we (mammals?) have more cell types that other species. Therefore, we are more complex. The number that's often bandied about is 210 cell types. PZ Myers debunks this myth (once again) in Methinks it is like a fox terrier". I love it when people like PZ make oblique references to Stephen Jay Gould as he does in the title. If you don't know what this has to do with fox terriers then you're in for a double treat.


9 comments :

  1. "One of the minor arguments in favor of human exceptionalism is the idea that we (mammals?) have more cell types that other species." And narwhals are the only cetaceans with a tusk. I guess that argues in favour of Monodon exceptionalism.

    Dave Bailey

    ReplyDelete
  2. This comment has been removed by the author.

    ReplyDelete
    Replies
    1. We should expect that a mammal will have more cell types than a nematode. Beyond that, the level of confidence that mammals have more should start to decrease. Between a mammal and an insect? We probably have more, but methinks the confidence that it would be significantly more should start to waver a bit. Remember that they will have cell types that we don't and vice versa. How about a mammal and a decapod crustacean? Mmm, not so sure. I used to do research on them, and they are complex. They actually have chambered hearts and an extensive network of blood vessels, right out to capillary beds. A mammal and a fish? I would not want to bet that we mammals have more cell types. Remember too that the info we have on 'cell types' is really very poor.

      Delete
  3. Every species has some unique characteristic, otherwise it wouldn't be a species. Is this really all they can do?

    Dave Bailey

    ReplyDelete
    Replies
    1. I've been studying variation in a group of Sedum (stonecrops -- plants, for any irredeemably animal chauvinists). In this group, it seems as if there are a dozen highly variable traits, each with two or three states, and each species has a different combination of these traits. No species has a unique characteristic, though each has a unique combination of characteristics.

      (I'm not arguing seriously here, just commenting based on the plants that are filling my brain just now.)

      Delete
    2. I love seeing mossy stonecrop covering the rocks in the summer, gorgeous plant.

      Dave Bailey

      Delete
  4. I love it when people like PZ make oblique references ...

    Oblique references to Gould and Dawkins in the same title. Wins a small prize.

    ReplyDelete
  5. It's an established fact that Republicans have 100 cell types, and Democrats have 200.

    No, really. It's been proven.

    Also, people who are fans of Insane Clown Posse have 50 cell types, and fans of Lyle Lovett have 250.

    ReplyDelete