Pleistocene's Extinction

Introduction:

The exact reason for the Pleistocene extinction is still not known, this data implies that top-down forces and humans are the reason the extinction happened. This data is important because during the Anthropocene humans continue to put animals at risk for another extinction. The authors used data from the Pleistocene and recent data to show that high rates of predation and humans could have lead to the extinction. Both carnivores and humans caused the extinction, because both were competing for prey which lead to a lower percentage of megafauna.

Methods Section:

The evidence used in this data comes from tusk growth rates, they also used tusk growth rates to figure out the age of maturation of mastodons.
Herbivores are on the right side and carnivores are shown on the left side. The yellow/light green areas had high megafaunal diversity and low loss. The dark green demonstrates low diversity and low loss. Red demonstrates high diversity and high loss, and dark brown is low diversity and high loss.

Data/Results Section: The first figure tested for food restricted megafauna, this was done by examining the annual growth of increments (rings) on fossil mammoth tusks (teeth). The data includes the growth rates at nine sites for males and seven sites for females, all coming from different places in North America. The dates range from 42.0 thousand to about 10.8 thousand years before present, all the dates are uncalibrated radiocarbon years.

Figure 1 Description: Mammoth tusk thickness growth rates coming from 16 different locations in North America. Each of the points represents the mean increment thickness for only one mammoth, however, the point at 26 thousand ybp for males, represents the average increment thickness of eight mammoths. The number of annual increments per mammoth ranged from 1 to 12, the sample mean is
For females, locations include Field Museum, Arkansas; Lamb Springs, Colorado; Maine State Museum, Maine; Hunter Ranch, Wyoming Colby, Wyoming; Chittenango, New York; and Dem, Colorado.

Furthermore, from the tusk growth patterns the age of sexual maturity of mammals like mastodons can be read. In Figure 2 they used seven male mastodons and three female mastodons from the Great Lakes region, dated from around 12.0 thousand to 9.6 thousand ybp.

Figure 2 description: On the x-axis it’s the radiocarbon ages and the y-axis shows the estimated age of maturation of mastodons. These mastodons are all from the Great Lakes region. The horizontal bars demonstrate uncertainties of the dates for the mastodons. The age of maturation seems to be lower as the graph moves to the right.

The third figure shows the rates of dental wear and fracture of Pleistocene carnivores and existent carnivores. The data shows that extinct carnivores had a higher percentage of broken teeth, with the highest being around 12.5 percent. The existent carnivores percentage of broken teeth are lower, the highest percentage for existent carnivores being around 5