A r j e meylan dating
For viral phylogenetics and ancient DNA studies—two areas of evolutionary biology where it is possible to sample sequences over an evolutionary timescale—the dates of the intermediate samples can be used to more precisely calibrate the molecular clock.
However, most phylogenies require that the molecular clock be calibrated against independent evidence about dates, such as the fossil record.
If most changes seen during molecular evolution are neutral, then fixations in a population will accumulate at a clock-rate that is equal to the rate of neutral mutations in an individual.
The molecular clock alone can only say that one time period is twice as long as another: it cannot assign concrete dates.
Proboscideans from these localities comprise 11 families, 27 genera, and 53 species.
Similarly, all vertebrate cytochrome c should be equally different from the yeast protein." For example, the difference between the cytochrome c of a carp and a frog, turtle, chicken, rabbit, and horse is a very constant 13% to 14%.
The biomolecular data used for such calculations are usually nucleotide sequences for DNA or amino acid sequences for proteins.
The benchmarks for determining the mutation rate are often fossil or archaeological dates.
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.
If this is correct, the cytochrome c of all mammals should be equally different from the cytochrome c of all birds.