The Pleistocene Overkill

There are two versions of what falls under the Pleistocene Overkill Hypothesis: Blitzkrieg, and Anthropogenic.

Blitzkrieg is the theory developed by Paul S. Martin and H.E. Wright (Pleistocene Extinctions: The Search for a Cause (1967) in the 1960s when many paleontologists and archaeologists first started noticing patterns linking megafaunal extinctions with human colonization of new territories. Paul Martin theorized that humans were responsible for the demise of many of the land mammals (larger than 50 Kg) beginning 10,000 years ago, and that these extinctions a) occurred very rapidly (within ~1,000 years) and b) they were due to overhunting. 'Blitzkrieg' is the term Martin used for the rapid, almost stormtrooper-like hunting assault on large animals that wiped them out. For Blitzkrieg to work, humans needed to be constantly on the move, killing huge swaths of animals in their path as hunters made their way across continents. The extinctions needed to occur within 1,000 years or less.

Anthropogenic is the more general overkill theory that merely states humans were mostly or solely responsible for the demise of Pleistocene era megafauna. The hunting needn't be rapid, nor do the animals actually need to have been hunted. As long as the extinctions can be tied to human predation or causation in some way (e.g. hunting, competition for resources, driving animals into smaller habitats, etc)then it falls under the more general 'overkill' theory.

There is actually some good evidence for overkill in general, but the more specific blitzkrieg model is not holding up well, as archaeological dating keeps pushing back human arrival in various continents further and further back in time. It now seems less likely that humans could have killed off so many different types of animals within a thousand years. But even the general overkill theory seems shaky at this point, as more and more climate scientists discover how volatile and different the climate of the terminal Pleistocene age really was.

Paul Martin vigorously defended his theory until his death in 2010. Blitzkrieg faced a lot of opposition, especially in the early days. But Martin was also open to criticism. He organized many conferences on the subject, and the debates both for and against overkill were hotly contested. Later on, Martin was actually a champion of the rewilding and de-extinction movement, which advocates for the reintroduction of extinct animals back into present day environments.

Of course, logically, the explanation for Pleistocene extinctions doesn't have to be shoehorned into either/or. Both climate and humans could have had causal effects on the megafauna. A few years ago I emailed Donald Grayson about the topic. He leans toward climate as the cause, but he told me that nothing is settled yet. He said the only real way to get at the cause is to map the evolutionary life cycles of each genera of animal (what's known as historic biogeography) and trace its pathway over the last third of the Pleistocene . This is already happening to some degree, but it requires many more paleontological researchers around the world dedicated to specific animals.

So, overkill (both blitzkrieg and anthropogenic) has not been 'debunked' quite yet. But it is on the ropes.