"But for 20 years or so the current dominant theory has suggested that their diversification happened more than 80 million years ago, well before dinosaurs became extinct."It now appears that the major diversification of placental mammals closely followed the extinction of dinosaurs 66 million years ago, an event that would have opened up ecological space for mammals to evolve into." Dr Phillips said that for molecular dating to work, scientists had to calibrate the rate of DNA evolution with fossils of known age.and delivered at the Society for Molecular Biology and Evolution Conference this week, Dr Phillips said biases in models of DNA evolution inflated estimates of when modern mammals, which were once no larger than a guinea pig, diversified and evolved into the animals familiar to us today."We can infer that some placental mammals did co-exist with dinosaurs," he said."I re-examined fossil calibrations, excluding those that were contentious or based on poorly resolved fossil placements and also fossil calibrations from within groups of very large or long-lived mammals, such as whales, for which parallel changes in the rate of DNA evolution in different lineages could distort dating estimates."When I took the remaining set of calibrations, the major diversification of placental mammals coincided with the extinction of dinosaurs," Dr Phillips said.
Since fish diverges from the main stem of vertebrate evolution earlier than either birds or mammals, the cytochrome c of both mammals and birds should be equally different from the cytochrome c of fish.This is the account of the discovery of a skull that has the potential to change what we know about human evolution, and a suppression and cover-up which followed.In 1959, in an area called Chalkidiki in Petralona, Northern Greece, a shepherd came across a small opening to a cave, which became visible when a thick covering of snow finally melted.They generalized this observation to assert that the rate of evolutionary change of any specified protein was approximately constant over time and over different lineages (based on the molecular clock hypothesis (MCH)).The genetic equidistance phenomenon was first noted in 1963 by Emanuel Margoliash, who wrote: "It appears that the number of residue differences between cytochrome c of any two species is mostly conditioned by the time elapsed since the lines of evolution leading to these two species originally diverged.the age of the earth and the universe, and that includes the ones we have listed here.