A biologist writes that one key period of evolutionary ferment, long before the emergence of modern humans, was between two and a half and two million years ago.
So the Chad discovery opens a window on a fateful period in evolutionary history about which the fossil record has been so sparse that the remains could fit in a shoebox.
The extraordinary remains are thought to represent a period of evolutionary transition between tree-dwelling apes and the earliest human ancestors, or hominids, to take their first tentative steps on two feet.
But even if the jaw alterations were due to natural selection, she concludes, they would have taken place over a relatively short period of evolutionary time.
It was no coincidence that oralist theory began to transform deaf education in the United States during the same period that evolutionary theory was radically changing how Americans defined themselves and their world.
Ancient samples of the microbes indicate that they have remained essentially unchanged for the past 2.3 billion years the longest period of evolutionary stasis ever discovered, according to The Washington Post.
Information about average selective forces at a locus, over a longer period of evolutionary history, can be obtained from the level and patterns of nucleotide substitution between two closely related species.
Genetic distances between well supported clades (mean of 10.6% Kimura 2-parameter) are consistent with a lengthy period of evolutionary independence between the two sibling species [32], reflected in the substantial genetic distance between the two invasive haplotypes (10.1%).
First, the strongest refractory period to evolutionary change across ontogeny takes place when organogenesis begins during the early zygotic stage.
This subfunctionalization may occur immediately after polyploidization or may arise over a longer period of evolutionary resolution [ 13, 14].
