Pleistocene
From EvoWiki
| Pleistocene |
|---|
| 1.8mya - 11,000 yrs |
| Epoch: Cenozoic |
| Period: Quaternary |
| Preceded by Pliocene of Tertiary |
| Followed by Holocene |
The Pleistocene is the first and dominant (considering time represented) epoch of the Quaternary period of the Geological timescale. The Pleistocene covers the interval from 1.8 million to 11 thousand years ago.
Contents |
[edit] Time period
The Pleistocene was originally considered coincident with the ice ages. It is now recognized that the ice ages began during the Pliocene epoch. Some geologists however, consider the Pleistocene concurrent with both the Plio-Pleistocene glaciations and the emergence of the genus Homo and place the start of the epoch at 2.5 million years ago rather than 1.8 million.
[edit] Recurring glaciation
The Pleistocene was a period of recurring glaciation, at least four periods of glacial advance with intervening warm interglacial events. These interglacial warm periods lasted longer than the 11,000 years that have elapsed since the last glacial retreat and the end of the Pleistocene. This has prompted many to consider the current Holocene epoch as only the current interglacial event and implying a return of ice age conditions or glacial advance in the future. Global warming may prevent this.
[edit] Emergence of modern humans & Extinctions
During the Pleistocene Modern humans evolved and began their global dispersion. Many large mammal species became extinct during the later part of the Pleistocene. These include the mammoth, mastodon, saber toothed cat, short-faced bear, giant sloth, and the North American camels and horses. The Pleistocene also saw the extinction of other human species, including the Neanderthal (Homo neanderthalensis), and the Ebu Gogo (Homo floresiensis). The recurring climate fluctuations certainly stressed many species and the hunting abilities of the evolving humans may have been a factor.
[edit] Cyclical glaciation
The cyclical glaciation periods end of the Pleistocene repeatedly tied up vast amounts of water as continental glaciers and resulted in drastically lowered sea levels. This allowed the migration of species across previously impassable barriers and the colonization of new territory. The return of higher sea level isolated the colonists allowing differentadaptations in different populations. This repeated migration and isolation has important evolutionary implications. One of the most interesting and widely studied is the area around the Bering Strait which was exposed as grassy steppe and allowed migration of early humans and many animal species between Eurasia and the Americas. This region is referred to as the subcontinent of Beringia and is the subject of intense study.
The Pleistocene Epoch roughly corresponds to the Paleolithic (old stone age) of archaeology.
