Extinction through time; were humans a factor in the past, too?

By Gloria Lima

It’s known that humans have played a large role in the extinction of many organisms. But does this mean we are the only cause? How is it possible for us to tell if we are the only factor or if we simply play a large role in the whole ordeal? Paleoecology offers clues, starting with which organisms went extinct, and which survived. We can look to paleontological data for patterns, like the body size of extinct species, or how those species interacted with their habitats.  By comparing fossil and modern animals, it is then possible to see how the organisms in the past interacted with their environments, by looking at the ecology of their surviving relatives.

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Image courtesy of Smithsonian Magazine.

Much of what we know about extinction comes from carbon dating the remains of extinct animals. An example is seen in the article “Patterns of generic extinction in the fossil record.” The authors looked at many fossils from a wide range of genera to see if there was a common pattern in extinction among the organisms. If there was a trend, it’s then possible to see whether the environment played a large role in the extinction, compared to the biology of the organisms. If so, this could mean that the climate caused a change in the environment before the organisms were able to adapt to it. Continue reading

The Hyper-Disease Hypothesis: Did Humans Bring About Doomsday for the Megafauna of the Pleistocene?

By Erika Lyon

It is a concern that we are entering Earth’s 6th mass extinction.  Mass extinctions occur when a large number of species die off in a short amount of time relative to background extinction rates (to read more about extinctions, click here).   Some of the major questions being asked include what are the mechanisms behind extinction events and could humans possibly cause a mass extinction?  One of the more recent extinctions in geologic time that may provide some insight into these questions is the Pleistocene megafaunal extinction that occurred in North America.  Three hypotheses have been made on the cause of the Pleistocene extinction, which include: 1) vegetation and climate change, 2) over-hunting by humans, and 3) the introduction of disease brought into North America by humans, the last of which is known as the hyper-disease hypothesis (MacPhee and Marx 1997; Lyons et al. 2004).  Continue reading