Question

Which of the following most logically completes the argument below?
Alone among living species, human beings experience adolescence, a period of accelerated physical growth prior to full maturity. Whether other hominid species, which are now all extinct and are known only through the fossil record, went through adolescence cannot be known, since

• A. the minimum acceleration in physical growth that would indicate adolescence might differ according to species
• B. the fossil record, though steadily expanding, will always remain incomplete
• C. detecting the adolescent growth spurt requires measurements on the same individual at different ages
• D. complete skeletons of extinct hominids are extremely rare
• E. human beings might be the first species to benefit from the survival advantages, if any, conferred by adolescence

Hint:

In "complete the argument" questions, look for the choice that provides the most direct and logical bridge between the premises and the stated conclusion. The conclusion here is "cannot be known," so the correct answer must explain \textit{why} it's impossible to know, based on the specific evidence available (fossils).

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
This is a "complete the argument" question. The argument states that we cannot know if extinct hominid species experienced adolescence. The correct answer will provide the most direct and logical reason \textit{why} the available evidence (the fossil record) is insufficient to determine this.
Step 2: Detailed Explanation:
The argument's core is about the difficulty of detecting adolescence in the fossil record. Adolescence is defined as a "period of accelerated physical growth." To detect a period of accelerated growth, one would need to track the growth of an individual over time. The fossil record consists of static remains of many different individuals who died at various ages. It does not provide a timeline of growth for a single individual. Let's evaluate the options based on this understanding:

(A) This suggests a difficulty in defining adolescence, but not a fundamental reason why it's impossible to detect from the fossil record.
(B) While the fossil record is incomplete, this is a very general statement. It doesn't explain the specific problem of detecting a \textit{growth spurt}.
(C) This pinpoints the exact methodological problem. To detect a growth spurt (a rate of change), one must have data points from the same individual at multiple points in time (e.g., age 10, 12, 14) to see the acceleration. The fossil record, which consists of different individuals, cannot provide this longitudinal data. This is a very strong and specific reason why the question cannot be answered.
(D) While the rarity of complete skeletons makes studying extinct hominids difficult, it doesn't make it logically impossible to detect growth patterns if you had enough partial skeletons of different ages. The core problem isn't the completeness of the skeletons, but the inability to track a single individual's growth.
(E) This discusses the potential evolutionary advantages of adolescence, which is irrelevant to the question of how we could detect it in the fossil record.
Step 3: Final Answer:
The argument is best completed by explaining the specific evidence required to detect a growth spurt and why the fossil record cannot provide that evidence. Option (C) does this perfectly.