Answer:
Arboreal hypothesis suggest that primates have the unique features, such as opposable thumbs which occurs due to the adaptation of the body to the external environment.
Step-by-step explanation:
Primates are those organisms that have some unique characters which are not present in other mammals such as their brain has big in size and there is a gap between fingers which helps them to hold things more precisely and tightly. These organisms belongs to kingdom animalia, class mammalia and order primates. Example of primates are monkeys and humans etc.