It might reasonably have been expected that the adoption of cooking by

It might reasonably have been expected that the
adoption of cooking by early humans would not have
led to any changes in human digestive anatomy. After
all, cooking makes food easier to eat, which means
(5) that no special adaptations are required to process
cooked food. However, current evidence suggests that
humans today are capable of living on raw food only
under unusual circumstances, such as a relatively
sedentary lifestyle in a well supported urban
(10) environment. Important theoretical obstacles to living
on raw food in the wild today include both the low
digestibility of much raw plant food, and the toughness
of much raw meat. These points suggest that humans
are so evolutionarily constrained to eating foods that
(15) are digestible and easily chewed that cooking is
normally obligatory. Furthermore, the widespread
assumption that cooking could not have had any
impact on biological evolution because its practice is
too recent appears to be wrong. (Various European
(20) and Middle Eastern sites that go back more than
250,000 years contain extensive evidence of hominid
use of fire and apparent “earth ovens.”) The implication
is that the adoption of cooked food created opportunities
for humans to use diets of high caloric density more
(25) efficiently. Selection for such efficiency, we suggest,
led to an inability to survive on raw-food diets in
the wild.

Important questions therefore arise concerning
what limits the ability of humans to utilize raw food.
(30) The principal effect of cooking considered to date has
been a reduction in tooth and jaw size over evolutionary
time. Human tooth and jaw size show signs of
decreasing approximately 100,000 years ago; we
suggest that this was a consequence of eating cooked
(35) food. Subsequent population variation in the extent
and timing of dental reduction is broadly explicable by
regional variation in the times when improvements in
cooking technology were adopted. It is also possible
that the earliest impact of cooking was the reduction
(40) of tooth and jaw size that accompanied the evolution
of Homo ergaster approximately 1.9 million years ago.
If so, the decrease in tooth and jaw size that started
around 100,000 years ago may prove to result from
later modifications in cooking technique, such as the
(45) adoption of boiling.

The evolution of soft parts of the digestive system
is harder to reconstruct because they leave no fossil
record. Human digestive anatomy differs from that of
the other great apes in ways that have traditionally
(50) been explained as adaptations to a high raw-meat
diet. Differences include the smaller gut volume, longer
small intestine, and smaller colon. All such features
are essentially adaptations to a diet of relatively high
caloric density, however, and may therefore be at least
(55) as well explained by the adoption of cooking as by
eating raw meat. Testing between the cooking and
raw-meat models for understanding human digestive
anatomy is therefore warranted.

1. Which one of the following most accurately states the main point of the passage?

(A) Important questions about why humans are unable to survive on raw food are unresolved by current science.
(B) Current evidence suggests that human beings are biologically adapted to the ingestion of cooked rather than raw food.
(C) The reduction of human tooth and jaw size over evolutionary time strongly suggests that humans underwent a change in their dietary habits.
(D) For at least 250,000 years, humans have been eating a diet that heavily features cooked food.
(E) No special biological adaptations were necessary for humans to eat cooked food, since cooking makes food easier to eat.

2. The authors would be most likely to agree with which one of the following statements?

(A) Small teeth and jaws limit the ability of humans to routinely utilize raw food.
(B) Because of its reliance on plants in its diet, Homo ergaster had a smaller intestinal volume than modern humans do.
(C) Early humans did not utilize plants for food prior to the adoption of cooking.
(D) The properties of the human digestive anatomy are primarily the result of adaptation to a high-meat diet.
(E) The human digestive anatomy has changed little over evolutionary time.

3. The primary purpose of the parenthetical sentence near the end of the first paragraph is to

(A) identify the amount of time that is required for a behavior to have had an impact on biological evolution
(B) provide support for the idea that cooking has been practiced for a relatively long time
(C) pinpoint the time and place when humans became unable to survive on raw-food diets
(D) undercut the suggestion that the adoption of cooking affected the evolution of the human digestive anatomy
(E) indicate the particular technology that early humans used to cook food

4. The authors would be most likely to agree with which one of the following statements?

(A) A raw-food diet is significantly healthier for modern humans than a traditional diet.
(B) Humans would not be able to utilize cooked food in their diet if during their evolution they had not biologically adapted to it.
(C) Early humans controlled fire long before they adopted the practice of cooking their food.
(D) The practice of eating a diet of cooked food did not become standard until humans were able to lead relatively sedentary lives.
(E) Empirical evidence does not yet definitively show that early humans developed biological adaptations to a diet of cooked food.

5. Which one of the following most accurately describes the structure of the passage?

(A) The first paragraph outlines a scientific hypothesis's two predictions, the second paragraph describes the empirical confirmation of the first prediction, and the third paragraph describes the empirical disconfirmation of the second prediction.
(B) The first paragraph describes a scientific theory, the second paragraph considers an alternative to that theory, and the third paragraph describes the empirical test that would show which theory is correct.
(C) The first paragraph argues for a claim, the
second paragraph explores a possible objection to that claim, and the third paragraph responds to that objection.
(D) The second and third paragraphs describe the
empirical predictions that clarify the difference between the two proposals outlined in the first paragraph.
(E) The second and third paragraphs explore the
possible empirical implications of a claim made in the first paragraph.

6. Which one of the following, if true, would provide the most support for the authors' claim in the sentence immediately preceding the parenthetical remark in the first paragraph?

(A) Evidence from cut marks on animal bones suggests that early humans' hominid ancestors used stone flake tools to butcher animals.
(B) Human populations are estimated to have adapted biologically to drinking the milk of domesticated animals in 5,000 years or less.
(C) Archaeological evidence indicates that the adoption of fire use by humans coincided with climatic changes that produced ice ages.
(D) An increase in the quantities of the trace element strontium in bones of early humans indicates an increase in the quantity of plant foods in their diet.
(E) The fossil record indicates that the brain volume of hominid species started growing after tooth and jaw size started decreasing.

7. The authors suggest which one of the following in the second paragraph?

(A) Human teeth and jaws underwent their only major reduction in size about 100,000 years ago.
(B) Adaptation to cooked food limited the ability of humans to survive on a high-meat diet.
(C) The evolution of the human digestive system is not well understood.
(D) Cooking methods changed and improved over evolutionary time.
(E) Cooking was adopted by geographically diverse early human populations at the same time.

8. The authors' primary purpose in the passage is to

(A) describe a scientific puzzle
(B) identify a common scientific misconception
(C) elucidate the meaning of a scientific hypothesis
(D) propose a scientific hypothesis
(E) undermine the support for a scientific principle