According to the arboreal theory, what adaptation did early primates undergo?

The choice regarding reduction in snout length and the development of front-facing eyes aligns well with the arboreal theory. This theory posits that early primates adapted to life in the trees, which influenced their physical features. The reduction in snout length would facilitate a better field of vision, while front-facing eyes provide depth perception, critical for navigating the complex three-dimensional environment of the forest canopy. This enhancement in visual acuity was essential for spotting food and predators, as well as for social interactions among primates.

In contrast, the other options do not directly connect to the arboreal lifestyle in the same way. For example, while longer tails can provide balance for some species, this adaptation is more related to specific locomotion methods rather than a general arboreal adaptation. Similarly, while broader shoulders and increased body size can assist in climbing or heat conservation, they do not specifically address the primary characteristics of early primates emphasized in the arboreal theory. Thus, option B illustrates the key adaptations that would have been most beneficial for survival and efficiency in a treetop environment.