In most vertebrate species, somatic growth decelerates as reproductive maturity approaches. Humans constitute a notable exception: they undergo a pronounced acceleration of skeletal and muscular development during puberty - a phenomenon widely termed the adolescent growth spurt - that is readily observable and involves the body in its entirety. Whether comparable spurts occur in non-human primates has remained a matter of dispute. Fieldwork conducted in the early 1970s by primatologist Owen Marsh, based on longitudinal measurements of captive orangutans, yielded no evidence of pubertal growth acceleration in those animals. A subsequent reanalysis of Marsh's original measurements by developmental biologist Carla Reiss, however, identified a statistically significant uptick in the rate of longbone elongation as the subjects neared reproductive maturity. The consensus among primate researchers nonetheless remains skeptical. Unlike the human spurt - which produces visible changes in stature and body proportion detectable by ordinary observation - the acceleration Reiss describes can be identified only by applying multivariate regression modeling to the raw data. Furthermore, anatomist Paulo Figueira has noted that the orangutan acceleration appears to commence when the animals have already achieved approximately 88 % of their eventual adult skeletal dimensions, compared with the roughly 76 % threshold at which the human pubertal spurt typically begins.

Which of the following best describes the main idea of the passage?
- A. Longitudinal fieldwork on captive orangutans has repeatedly failed to produce evidence of a pubertal growth spurt, regardless of the analytical methods applied
- B. Although recent reanalysis has identified a possible growth acceleration in orangutans at reproductive maturity, the prevailing view among researchers remains that it is not comparable to the human adolescent spurt
- C. The debate over whether orangutans experience an adolescent growth spurt has been definitively resolved by Reiss's application of multivariate regression modeling
- D. Marsh's original fieldwork was methodologically flawed, which explains why it failed to detect the growth acceleration that Reiss subsequently identified
- E. Orangutans and humans share a pattern of pubertal growth acceleration that is now supported by both observational and statistical evidence



According to the passage, which of the following is cited as a reason why primate researchers remain skeptical that orangutans experience a humanlike adolescent growth spurt?

- A. The growth acceleration Reiss identified begins only after the animals have reached full reproductive maturity
- B. Marsh's original data were collected under captive conditions that may not reflect the growth patterns of wild populations
- C. The acceleration Reiss describes produces no visible change in body proportion that can be detected through ordinary observation
- D. Reiss's multivariate regression modeling has not been independently replicated by other researchers
- E. The growth rate increase in orangutans is too brief in duration to constitute a genuine developmental stage



The passage suggests which of the following about the adolescent growth spurt in humans?

- A. Its onset occurs at a point when a greater proportion of full skeletal growth has already been completed than is the case in orangutans
- B. It is identifiable through direct observation without recourse to statistical modeling
- C. Its most pronounced effects are concentrated in the long bones of the limbs rather than in overall stature
- D. It has been more thoroughly studied than the comparable phenomenon in any other primate species
- E. The 76 % skeletal threshold at which it begins has been established through multivariate regression analysis