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LET’S SUPPOSE that we are interested in studying the evolution of the squamates, the snakes and lizards. We know that if we track down the evolutionary tree of the squamates we find that they are lepidosauromorphs, and a sister group to the archosauromorphs. Ah-hah! The archosauromorphs diverged before the evolution of the lizards, so living archosauromorphs must preserve ancestral traits, we think. So we go forth and find an archosauromorph and sequence its genome. There are multiple species from which to choose, but we grab the closest one—the European starling. Since this is an archosauromorph and early diverging compared to the snakes and lizards that must mean that it is “primitive”.
Does this seem odd to you?
We’ve had a blitz of platypus genome papers this week, with a brand new article on the platypus genome sequence in Nature and several papers on specific aspects of this genome showing up in Genome Research. I hope to cover a couple of these in the next week. It’s been a while since my last update because I’ve been very busy, but I’ll take a look at the platypus genome paper itself tomorrow and hopefully follow-up Sunday or Monday with some of the information from Genome Research.
Of course this discovery has led to more bad reporting, and from reading the news outlet articles it looks like the scientists involved are contributing to some of it! Some of the things they are saying are not wrong, but possibly misleading. I’ll go into that a little bit tomorrow. For now let’s say I keep seeing the word “primitive”, and the New York Times refers to monotremes as “offshoots of the main mammalian lineage”. Well, I personally think the placentals and marsupials are branches off that most noble main mammalian lineage, the sadly extinct multituberculates.
I MENTIONED in a recent post that 75% of all of the types of mammals that have ever lived are now extinct. We have a tendency to think of extant organisms as all there is. We know dinosaurs once lived and are now extinct, but you’d be hard-pressed to get the average person to name one major extinct non-dinosaurian group. Yet we don’t have to look very far into our own past to find many of them.