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A recent study has provided clues to
predator-prey dynamics in the late Pleistocene
era. Researchers compared the number of tooth
fractures in present-day carnivores with tooth
fractures in carnivores that lived 36,000 to 10,000
years ago and that were preserved in the Rancho
La Brea tar pits in Los Angeles. The breakage
frequencies in the extinct species were strikingly
higher than those in the present-day species.
In considering possible explanations for this
finding, the researchers dismissed demographic bias
because older individuals were not overrepresented
in the fossil samples. They rejected preservational
bias because a total absence of breakage in two
extinct species demonstrated that the fractures
were not the result of abrasion within the pits.
They ruled out local bias because breakage data
obtained from other Pleistocene sites were similar
to the La Brea data. The explanation they consider
most plausible is behavioral differences between
extinct and present-day carnivores—in particular,
more contact between the teeth of predators and
the bones of prey due to more thorough
consumption of carcasses by the extinct species.
Such thorough carcass consumption implies to
the researchers either that prey availability was
low, at least seasonally, or that there was intense
competition over kills and a high rate of carcass
theft due to relatively high predator densities.
4The primary purpose of the passage is to
(A) present several explanations for a well-known
fact
(B) suggest alternative methods for resolving a
debate
(C) argue in favor of a controversial theory
(D) question the methodology used in a study
(E) discusstheimplications of a research finding
