Mike the Mad Biologist

Teaching Macro- and Microevolution

There have been a lot of comments on this post about using molecular evolution to teach evolutionary biology. A couple of people were worried that creationists will look at molecular data and claim that it is ‘microevolution’ and thus compatible with creationism (I’ve dealt with the creationists’ macroevolution canard before). I’m not worried about this issue.

First, even when a study (or project) is focused on a single species, if you’re building trees, then you typically need an outgroup (sequence from another species). And now, once again, we’re in the world of common descent….and then creationist’s head go boom. Second, many techniques use both intraspecies polymorphism (DNA variation found within a species) and interspecies divergence (DNA variation among species that is not variable within a species). Once again, we’re back in the wacky world of macroevolution. Finally, some of the best ‘natural history’ examples of molecular evolution are interspecific. For example, in langur monkeys, which have foregut fermentation just like cows do (screwy, but true), langurs and cows both secrete lysozyme into the stomach to break down the fermentation bacteria. The langur lysozyme has evolved at a much faster rate than other primates, and many of these changes make the langur lysozyme more similar to the cow lysozyme than other primate lysozymes. These changes have been shown experimentally to make lysozyme more effective in the highly acidic guts of ruminants. Note that I didn’t mention intraspecific variation (i.e., microevolution) once in all of this (the amino acid variation is fixed).

So I don’t think the ‘microevolution canard’ is much of an issue. And as other commenters noted, the advantage of molecular data is that the creationists don’t (yet) have bullshit lined up, ready to go.

Comments

  1. #1 Mike O'Risal
    August 29, 2008

    Of course, one can always test ID’s design inference with molecular data, too. Just us a random generator to put together a few 1400 bp sequences and then pull a real one from EntrezGene. Line them all up side-by-side and challenge the IDiots to pick the one that was designed out of the lot of randoms. Great fun at parties.

  2. #2 Andy
    August 29, 2008

    Wait, so isn’t this just an example of convergent evolution? Isn’t the evolution of lysozyme in this example intraspecific? It’s a change within a particular species, not found in related species (other monkeys) and apparently not involved in speciation. How does this example disprove so-called “macroevolution”?

    I’m a PhD student in genetics (i.e. not in evolutionary bio), but apparently totally lost on this issue.

    (PS: your third link is to an admin page)

  3. #3 Sandra Porter
    August 29, 2008

    Thanks Mike,

    For 3 years, I taught a NSF Chautauqua course for college instructors on using bioinformatics resources to teach evolution. I can give you lots of examples of things to do if you’re looking for them.

    There are many more things that you can do besides making phylogenetic trees from DNA and protein sequences. You can align 3D structures with VAST, look at intron and exon structures with the UCSC genome browser, look at drug resistance, look at the genetic code in different organisms; I can go on and on (that goes with being a blogger I guess).

    I have had high school interns though, who will still insist that evolution only applies to viruses and “animals” and not to humans. :-)

  4. #4 Ian
    August 29, 2008

    Mike – Your URL to “I’ve dealt with the creationists’ macroevolution canard before” goes to some sort of admin page which requires a log-in. Can you fix that for us, please?!

  5. #5 pough
    August 29, 2008

    Um… your second link is a link to the admin to edit the page, not to the page itself. You might want to change that… unless you’re also going to provide us with the username and password…? ;-)

  6. #6 pough
    August 29, 2008

    How did I not notice Ian’s comment? :-/

  7. #7 abb3w
    August 29, 2008

    Someone may find this illustration helpful. Of course, I’m not a biologist, I’m just a computer geek, so it may be completely wrong, but at least it’s pretty. =)

  8. #8 Andy
    August 29, 2008

    I’m not trolling with that above comment, even though it might appear so. I’m a big ol’ atheist who has no interest in creationism.

  9. #9 Rabbit
    August 29, 2008

    Wait, so isn’t this just an example of convergent evolution? Isn’t the evolution of lysozyme in this example intraspecific? It’s a change within a particular species, not found in related species (other monkeys) and apparently not involved in speciation. How does this example disprove so-called “macroevolution”?

    If I understood correctly, the amino acid sequence of the langur’s lysozyme is fixed within the species. In other words, there aren’t some langurs over here with a lysozyme that looks like a cow lysozyme and some langurs over there with some more monkey-like lysozyme.

    So I think the point was that this is an example of molecular evolution that supports (not disproves) macroevolution. But it’s the end of a long day so it’s very possible I misinterpreted.

    FWIW, I’m TAing evolution in the spring and I like the idea of teaching evolutionary biology with molecular evolution but I’m curious/nervous about how it will turn out.

  10. #10 Andy
    August 30, 2008

    First, I can’t figure out why I said “disprove” macroevolution, now that you’ve addressed it, Rabbit. I think I must have gotten confused – I should have written “supports”.

    I think I’m getting a little closer to understanding. I think he’s saying that the evolution of lysozyme is distinct in different species and can be traced through evolution. Which is fine, but I’d need to learn more about that specific example so that I could see it as evidence of macroevolution.

    Again, I’m a PhD student in genetics, with no anti-evolution sentiment. I’m just trying to figure out some stuff I don’t understand yet.

  11. #11 mirc
    March 14, 2009

    thanks