Four blind wisemen are examining a skull. The first grasps the tip of the tusk and shouts “it’s a spear!” The second feels the deep concave nasal cavity at the center of the skull and exclaims “no, it’s a cyclops, to be sure!” The third rubs the jagged molar and muses, “cyclopses don’t exist, but surely this was a fearsome carnivore.”
Then the fourth wiseman walks up and lightly taps the tip of the occipital condyle he probes the foramen magnum. Then he draws his finger up and across the low-domed skull and explores the depths of the nasal cavity. He carefully strokes each long conic incisor before moving deeper into jaw. He traces each cusp and groove along each tooth. After some time, the fourth scientist quietly states, “It’s a proboscidean, specifically an American Mastodon (Mammut americanum) or something like it.”
LOL! Genomics takes the old fable of the blind man and the elephant to heart. Rather than studying genetic information by examining minute bits (like only 10,000 base-pairs or something), or ‘genes’ the genomicists examine entire organimsal genomes, the forest rather than the trees if you’d like (alt. getting complete sets is no mean feat, even from a living organism.
That makes the announcement of the sequencing of an entire Mastodon mitochondrial genome from a tooth wrenched from the Alaskan permafrost totally effing astonishing. And really, really cool. Even better it’s been published in PLoS and is free for all to ponder, ruminate and expound upon.
One application of whole-genome studies is evolutionary comparison between related organisms. In this case, the researchers compared the Mastodon genome with living Asian and African Elephants as well as with the previously published genome similarly ‘back of the freezer’ Mammoths (Mammuthus primigenius). Here’s their tree:
Rohland et al 2007 image links to original, larger version.
The also compared these genomes to elephants’ closest living relatives, Hyraxes and Dugongs (remind me to write about Afrotheria some time…), as well as compared the rate of genetic change in proboscideans with other mammals, including primates.
Snap! (Skull tip to Afarensis)
Hey, what’s that thing by Charles Peale’s foot? A meat grinder? To be continued?