Biologists mapped crocodilian genomes

A Texas Tech University biologist led a team of more than 50 scientists who mapped the genomes of three crocodilians. Understanding the crocodilian genome can help scientists better understand the birds. The DNA in alligators, crocodiles and gharials is about 93 percent identical across the genome. In comparison, a human shares about 93 percent of his or her DNA with a macaque. One of the major finds in this case was that crocodilian genomes change very slowly when compared to birds. They compared both birds and crocodilians to turtles, which are the closest living relatives of the group that includes both birds and crocodilians. We found that they evolved slowly also. The best explanation for this is that the common ancestor of all three was a ‘slow evolver,’ which in turn suggests that rapid evolution is something that evolved independently in birds. They found the same pattern in all three species and the likelihood that all three were subject to the same genetic bottlenecks is small. It was suggested instead that change just occurs slowly in crocodilians. In other words, it wasn’t that the genetic differences were reduced because of overhunting. Rather, the amount of variation in crocodilians is low because change simply occurs slowly in these genomes. There is some fascinating biology in Crocodylia like temperature-dependent sex determination. Male and female crocodilians are genetically identical.