Evolution, with teeth

My last Seed column is online, which reminds me (as if I weren’t uncomfortably aware already) that I have to finish up the next one today, which actually isn’t the next one, which is already done and submitted, but the one after that. These long leading deadlines force one to live a few months in the future…

You know, if you subscribed to the print magazine, you’d be halfway to my future already instead of living in my distant past.


  1. says

    Don’t say that. I intend to beat this deadline by a few days. Of course, there are a few other deadlines that whooshed by recently and that I’m struggling to catch up with, too…

  2. Rob Welbourn says

    I’m happy to say that I subscribed to Seed as a result of reading this very blog.

    (More biology, fewer kreationist kooks, please!)

    Rob W

  3. Tilsim says

    Lovely column! Wouldn’t it be great if we could fiddle with those activators and inhibitors, and prepare ourselves a third set of teeth, and arrange for them to erupt at 60?

    Incidentally your term ‘Tooth Sculptor’ struck a chord with me. Maybe an idea for an illustrated children’s book? At the same time it could be one of the thousand epithets of the ‘Unnamed’ Designer.

  4. Thalience says

    I recently purchased a copy of Seed to read on the train ride between NYC and Philly, because I knew that you write for them. I enjoyed your article (although your blog posts are usually more in-depth). But as for the rest of the magazine, I was very disappointed. It was all pretty pictures and fluff pieces.

    An issue of Cosmo would have contained about as much science and would have had pictures of scantily clad females as an added bonus. Would not buy again.

  5. says

    Everyone wants more science here, but you’ve got to look at it from my side: I’m writing three magazine articles (one done and sent off, another in progress, and a third to get started on tonight), all science, just this week alone … on top of a full course load in my primary and most important job, teaching at UMM. I’ll write more science here if someone will mail me about 3 extra hours a day.

    Or you could just wait a bit. This semester ends in a week and a half, which will remove one angry, screaming gorilla from its perch on my shoulders.

  6. Thalience says

    PZ: To be clear, I do not intend to disparage your prodigious science output. I just pine for the days (?? – mid ’90s) when Scientific American articles had so much science in them that I had to read each one several times before I understood it. Now that was value for your science magazine dollar!

  7. says

    I was born without eight teeth, including wisdom teeth. I’ve always said it makes me more highly evolved…or does it just makes me stupider?

    I passed along the lack of wisdom teeth to my son.

  8. Lynnai says

    “Writing is 2% inspiration and 98% not getting distracted by the internet. :p”

    It’s so true! I’m sure Byron had it easier, all he had to contend with was wine, women, syphalis and a pet bear. Those were the good old days. Slashdot vs syphalis is simply not a fair fight.

  9. Anon says


    I’m on my third set of incisors, so I am more highly evolved than you are…. neener, neener…

    Anon (part shark since 1961)

  10. says

    In your column, you mention a mathematical equation that they used to model the growth patterns of teeth – is there a way you can link us to that? I’d love to plug that into a Matlab graph =)

  11. Confused says

    The semantics of the article confused me a little. I perked a little when you said that teeth were epigenetically specified – thinking you meant some kind of crazy para-genomic inheritance going on – and was a little disappointed when it was basically two genes interacting. Unless by “some kind of template or blueprint in your genome” you actually meant a drawing of a tooth sketched out in chromatin somewhere.

    I suppose coming from a (vertebrate) dev bio background, to me it stands to reason that the only way morphogenesis could happen is by the interaction of signalling molecules, rather than cell spontaneously assuming their identity as proscribed by the genome (although C. elegans people might dispute that). To me, that is genomic control, that is the genomic blueprint of a tooth – it’s not sketched out explicitly, but locked up in the subtle interactions between a dozen gene products activated in a certain context. I suppose you’re not wrong calling it epigenetic… it was just a little anticlimactic given I was expecting something a little less universal, I guess.

    On a side note, realising that miniscule genetic variations in this kind of machinery can have relatively large effects on morphology was one of the last nails in the intelligent design coffin for me. (I’m sorry – I used to be a day-age creationist. I have long since seen the light, though.)

  12. says

    those lovely permutations on a theme–are minimized by the use of subtle algorithmic variations, by rules and formulas that can only be discerned by looking beyond the genome to the epigenetic processes that shape the actual tissues.

    Good article…A+

    As one who was born with notoriously bad teeth which were all lost by my 40’s, I found it especially interesting.

    “looking beyond the genome to the epigenetic processes that shape the actual tissues.”

    Not only teeth, of course, but many other structures and adaptations. Epigenetic influences in general have been largely overlooked in evolution and development. Genes are only one piece of the development puzzle.

    “There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy”

  13. says

    So it’s not a tooth specification, it’s a tooth procedure. Or recipe (Take seeds, marinate in this, baste occasionally with essence of nearby tooth, grow for so long…).

    Two of my adult teeth never came in. I thought it was one of my approximately 300 mutations that we all have, but now it seems it might just have been a procedureal hitch.

  14. CJO says

    Good stuff. I remember when I first started reading about Chaos Theory and dynamic systems, and it seemed like everywhere I looked there were “simple” interactions giving rise to “complex” behavior.

    It just became obvious to me (and this was before Evo-Devo was in the popular press at all) that genomes weren’t specifying all the little details of growth and development, they were coding for gradients and interactions, and dreaded “chance and regularity” were sweating the little stuff. Good to know that my college-age “big idea” was a sound intuition, and now look! they done made a whole science out of it.

  15. gex says

    “I’m on my third set of incisors, so I am more highly evolved than you are…. neener, neener…”

    OT – but this reminded me of one of my pet peeves about fundies and such. They like to talk about what is “natural”. I’m sure everyone’s all sick of my “from my gay perspective” comments, but I’m always hearing about how one man, one woman is natural. These people willfully ignore that many people are born with traits of both. But since man and woman is the dominant norm, it must be the only natural thing.

  16. JM Inc. says

    #18: Exactly, gex.

    It’s positively shocking how much people in general, not just fundies, buy into this sort of “generalised familiarism” where things are defaulted to being either normal or abnormal (and by extension, value-judged to be “wrong”), with specified exceptions.

    We like to think we’re such an enlightened and liberal culture, but really we’re just as prejudiced and biased as we’ve ever been, and we merely happen to have an especially large list of “exceptions to the rule” (i.e. people of different colour, people of different political orientation [iffy], people of different abilities, people of different religious persuasion [iffy]). Real social progress and enlightenment doesn’t come with specifying “who among the outsiders are the good ones”, it comes with realising that no matter what differences there may be between people, of whatever magnitude, it is always, without exception, ethically inappropriate to discriminate for or against people on fundamentally irrelevant grounds.

    #6: Thalience, you might try “American Scientist”. That’s one of my favourite non-journal science magazines. The best pictures really are graphs, I agree. Seed is good, but it is as it professes to be; “Science Is Culture”. The magazine’s focus is more on issues in the scientific community and surrounding science policy, than on what the latest figures indicate, or what they dug up in the foothills of Armenia with implications for the history of agriculture.

    For example: I still smile when I think about an article in “American Scientist” I read over a cup of espresso in Starbuck’s, containing some recent genetic data and speculations about possible pathways in the evolution of bacteriorhodopsin.

  17. David Marjanović, OM says

    I’m on my third set of incisors

    Now that’s an atavism I’d like to share. Not that I need it so far, being only 25 years old, but when I look at my parents’ dentistry expenses…

    And yes, it is an atavism. Mammals are almost unique in having a restricted number of tooth replacement events. Thus, one of your mutations is a reversal.

    Two of my adult teeth never came in.

    The second upper incisors? And instead, the adult canines came through, and the milk canines never fell out? I’ve seen several people with this interesting condition; one of them was in my class at school and talked about the phenomenon once.

  18. David Marjanović, OM says

    …which I find interesting because it makes such people the first organisms since the Middle Permian (some 260 million years ago) to have two canines in a row.

  19. Eric says

    I saw the magazine at Great Clips. It really is a sexy looking magazine. I didn’t have a chance to read any of the word things, but a cursory glance through the magazine highlighted a bunch of articles I might be interested in.

  20. G.R. says

    Your description of your column schedule reminded me of this hilarious “Mr. Show” sketch: “The Pre-Taped Call-In Show”.

  21. chuckgoecke says

    PZ, this article was facinating! Although I’ve only had a little development bio, I seem to recall that similar mechanisms are at work in all tissue types developing in an embryo. Timing, proximity, concentration gradients, promoter and antagonistic chemicals all playing a part. The stunningly cool part that you’ve illustrated is how the control of all this can be quit simple, a few genes, a toolbox, what a cool concept! Thanks!

  22. says

    You could personally significantly reduce the heart attack rate among science fans if you’d just phrase it this way: “My latest Seed column . . .”

    Think of the humanity.

  23. themadlolscientist says

    I wish I could afford to subscribe to SEED magazine! I first encountered it in my doc’s office, of all places (someone must have made a mistake, putting something of substance in among all those golf and gossip rags). Since then I’ve bought 2 or 3 issues when I could find them and afford them at the same time. It’s on my short list of things to subscribe to if and when I ever get my money situation in some sort of shape (i.e. if I ever have any!).