M2: Lecture 6: Pleistocene Extinctions

When did the extinctions of large animals occur?

During the Late Pleistocene-Early Holocene

Who criticized New World fauna and what year?

Comte Buffon 1766

What did he criticize New World fauna as?

diminutive and degenerated

What were the Late Pleistocene conditions in the Las Vegas Valley during the LGM

Much more vegetation and canopy. A river allowing for wetland associated biodiversity. There was no evidence at this time of humans in the Las Vegas Valley during the LGM.

Name the two species of bison as large mammals in the Late Pleistocene

Two species of bison (Bison latifrons, B. antiquus)

How many types of horses were there in the Late Pleistocene period? Name them

Three types:

1. Large stout legged horses  (Equus scotti)

2. Small stout legged horses  (Equus sp.)

3. Small stilt legged horse (Haringtonhippus francisci)

What how many species of ground sloths were in the Late Pleistocene period? Name them

Two species:

1. Jefferson’s (Megalonyx jeffersonii)

2. Shasta (Nothrotheriops shastensis)

What were the other species of large mammals in the Late Pleistocene?

1. Yesterday’s Camel (Western Camel)

2. Dire wolf (Canis dirus)

3. Saber toothed cat

4. American lion

What were the three hypotheses on Extinction of Megafauna?

1. ‘Arrival’ of Clovis People

2. Erratic swings in climate

3. Combination of both

What was Beringia and what time was it around?

a land bridge used as a migration route during the Pleistocene epoch

More specifically, what was the classical interpretation for the first hypothesis on extinction of megafauna?

Clovis people were big game hunters that followed herds through Beringia and then south through an ice free corridor before 13,000 ya

When was their evidence of Clovis tools dated?

Roughly 13,400 ya

What was the Overkill Model of Megafauna Extinction Hypothesis?

Modern Homo sapiens were novel predators and ecosystem engineers by which they brought fire to use for hunting as well as ground traps

Who developed the Overkill Model of Megafauna Extinction Hypothesis and what year?

Paul Martin 1973

The extinction of megafauna was ___ ___ to North America

not limited to

Extinctions of megafauna was not ___ ___ to species climatic period across continents and why?

not temporarily linked

Because extinctions occurred across continents 50,000-10,000 years ago

What correlation was there extinction of megafauna and the arrival of Modern Homo sapiens?

Strong correlations

What continent was not similarly impacted from the megafauna extinction patterns?

Africa where megafauna was through to have coevolved with modern humans

What was the spatial-temporal correlation of the extinction of megafauna?

1. Distributions of Homo sapiens

2. Change in temperature

What was the Pleistocene hunting technology from the Clovis People?

Atlatl: spear thrower tool

• used to provide leverage for greater force and accuracy (velocity and distance)

• Clovis point

What was the Clovis Point

A fluted stone projectile points

What were two different hypothesis fro the arrival of humans in the Americas

1. Overkill hypothesis

2. Coastal Migration hypothesis

What evidence is there to support the overkilling of megafauna from humans in the Americas?

• Indisputable hunting of some extinct species

• Clustering of extinctions around first contact with Clovis people

• Widespread distribution of Clovis people

• Support from simulations of hunting impact

• More pronounced climate change that caused extinctions

Which piece of evidence has a problem to consider about the causes of extinction of megafauna?

More pronounced climate change

The issue with this is that there was already fluctuations in climate before then that species were able to live through. The Younger Dryas was fairly similar in fluctuations from those before so what makes this time the only reason why organisms went extinct?

What questioning is there for the Overkill Hypothesis?

• Correlative evidence that humans were primary drivers

• Assertions about human-environment interactions from this argument are untested

• Direct evidence of megafauna hunting by Pleistocene humans is rare despite there being strong evidence to hunting

• This argument has political connotations (supports environmentalist perspective that humans are wholly a destructive species

• There is data that humans may have arrived earlier in the Americas than the time of extinction and prior to the Clovis people

What was the coastal migration hypothesis?

Modern humans arrived much earlier in the Americas, following a coastal route by boat to jump from one ice-free patch to another, until arriving south of glaciers

What is the problem with the coastal migration hypothesis?

It assumes that Pre-Clovis People had their own technology an a more coastal life style and there’s not a lot of evidence.

Although there’s not a lot of evidence that Pre-Clovis people had their own technology, what data is there ?

• Non-Clovis style spear points and tools dating to 14,000-16,000 years ago

• Fossilized feces dating 14,300 years ago with mtDNA that match common DNA I Modern Native Americans

• Ancient fossilized foot prints 21,000-23,000 years old of children and teenagers

What was the evidence that supports the perspective that Clovis people did not migrate south from Beringia, instead their culture may have evolved in the Americas from people already here?

• Novel technology and culture development allowed for megafauna hunting by Clovis people

• Gaining access resources is not generally done pre-Clovis people

• Clovis people spread

After all this evidence, where does this leave us?

Evidences now seems to dispute traditional Clovis First Hypothesis, however it is fairly clear that Clovis People played a role in hunting, changing fire regimes

What speculations remains still?

Speculation regarding climate change that there was erratic swings in temp would have been difficult to tolerate. There is lots of speculation that both humans and climate were a combined effect.