Passage 37

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

(5)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 strik-

ingly higher than those in the present-day species.

In considering possible explanations for this finding,

(10)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 dem-

onstrated that the fractures were not the result of

(15)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 part-

(20)icular, 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

(25)was intense competition over kills and a high rate of

carcass theft due to relatively high predator densities.

234. The researchers’ conclusion concerning the absence of demographic bias would be most seriously undermined if it were found that

(A)   the older as individual carnivore is, the more likely it is to have a large number of tooth fratures

(B)   the average age at death of a present-day carnivores is greater than was the average age at death of a Pleistocene carnivore

(C)   in Pleistocene carnivore species, older individuals consumed carcasses as thoroughly as idd younger individuals

(D)  the methods used to determine animals’ ages in fossile samples tend to misidentify many older individuals as younger individuals

(E)   data concerning the ages of fossil samples cannot provide reliable information about behavioral differences between extinct carnivores and present-day carnivores