Mass extinctions over time
White-tailed deer frequent this open field. As recently as 10,000 years ago the fauna in this area would have been very different. As shown in The Pleistocene Extinction at the Beneski Museum of Natural History, the local wildlife population would have included the now-extinct American mastodon.
At the end of the Pleistocene time, when the climate changed at the end of the most recent glaciation and as human predation mounted, extinctions became more common. Large mammals like the American mastodon and Colombian mammoth on display in Beneski were especially hard hit.
Mass extinctions have occurred at least five times in the past 542 million years, but there is growing concern that human activity is causing a sixth mass extinction today. The causes of mass extinctions vary. At the end of the Cretaceous Period, 66 million years ago, a comet or asteroid about 10 kilometers in diameter struck what is now the Yucatan peninsula in Mexico. In the aftermath, large numbers of species, including all non-avian dinosaurs, were eradicated. The largest extinction occurred approximately 251 million years ago at the end of the Permian Period and obliterated an estimated 90% of all marine animal species. Unlike the sudden event at the end of the Cretaceous, the Permian extinction was more gradual, lasting tens of thousands of years. The causes of this extinction are still not well-known, but are likely related to global environmental changes associated with immense volcanic eruptions in what is now Siberia. This is important to keep in mind as human actions are dramatically altering the climate, and we don’t really know all the consequences.
