Dating the genetic bottleneck of the america cheetah summary
The animals living today are all descended from 12 individuals and they have extremely low genetic variation, which may be beginning to affect the reproductive ability of bulls (Luenser et al., 2005).
The population of American Bison fell due to overhunting, nearly leading to extinction around the year 1890 and has since begun to recover (see table).
In other words, all living humans' female line ancestry trace back to a single female (Mitochondrial Eve) at around 140,000 years ago.
Via the male line, all humans can trace their ancestry back to a single male (Y-chromosomal Adam) at around 60,000 to 90,000 years ago.
About 100,000 YBP the volcano erupted violently, burying much of the tortoise habitat deep in pumice and ash.
Researchers' DNA analysis dates the bottleneck around 88,000 years before present (YBP), according to a notice in Science, October 3, 2003.
The theory is based on geological evidences of sudden climate change, and on coalescence evidences of some genes (including mitochondrial DNA, Y-chromosome and some nuclear genes)However, such coalescence is genetically expected and does not, in itself, indicate a population bottleneck, because mitochondrial DNA and Y-chromosome DNA are only a small part of the entire genome, and are atypical in that they are inherited exclusively through the mother or through the father, respectively.
Most genes in the genome are inherited from either father or mother, thus can be traced back in time via either matrilineal or patrilineal ancestry.
They also increase inbreeding due to the reduced pool of possible mates (see small population size).
A slightly different sort of genetic bottleneck can occur if a small group becomes reproductively separated from the main population. Evolutionary biologist Richard Dawkins has postulated that human mitochondrial DNA (inherited only from one's mother) and Y chromosome DNA (from one's father) show coalescence at around 140,000 and 60,000 years ago respectively.