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

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Wildfire through time: shaped by climate and people

By Dulcinea Groff

Picture the landscape of a tropical savanna, composed of grasses, shrubs and a sparse number of trees.  The savanna biome is dominated by a wet season supplying thousands of herbivores with forage and a dry season accompanied by intense lightning and fire.  These wildfires maintain the savanna as grassland by killing the saplings (suppressing tree growth) and the grasses quickly regenerate.  Imagine early hominids in the fire-constructed savanna, they begin to use fire, control fire and even make it!  Fire is a permanent link now between biome and human.

Fire was used by humans for presumably many reasons:  communication, prepare food, drive and corral prey, warmth during cold periods, etc.  Humans have long suppressed and ignited fires for various reasons.  In fact, as a source of ignition, humans have been shaping landscapes since the earliest known hominids were thought to use fire one million years ago in South Africa (Berna et al. 2012). Continue reading