Question Description

person 1: After learning about the three hypotheses regarding primate evolution, I believe that Arboreal Hypothesis is the most plausible.

The main reason I support this argument is because I believe that adaptations like convergent eyes, and grasping hands were necessary for primate like creatures to evolve for tree-climbing. Convergent eyes developed to help primates see in front of them as they swung from branches and vines. If they did not evolve to have convergent eyes, than they would have to swing between branches with their head turned. Failure to evolve convergent eyes would also limit them with vision from one eye looking forward, versus two forward facing eyes which helps with depth perception. Grasping hands, long tails for balance, and even some prehensile tails were also a necessary adaptation for tree swinging and climbing as well.

Unfortunately, this hypothesis has a flaw to it. Technically, none of the adaptations above are necessary to live in trees. For example, squirrels successfully live in trees and have not evolved into primate-like creatures. However, there are different ways to adapt to one situation. While these features made sense for some creatures to evolve into primates, it was not necessary for all creatures who live in trees.

A second argument is that not all primates live in trees! It is true that multiple types of primates and forms of locomotion exist, such as Vertical clingers and leapers, Arboreal Quadrupedalism, Terrestrial Quadrupedalism, and Suspensory primates. However, I defend this second argument by suggesting that arboreal primates evolved first, and then progressed to the ground evolving features like knuckle walking and mobile wrist joints.

person2: I think that the angiosperm coevolution hypothesis is most likely to be correct out of the three hypotheses discussed in lecture this week. I am in support of this theory due to the fact that differentiating between edible or desirable angiosperms requires an elevated level of cognition which would explain primates’ larger brains. Additionally, this evolution hypothesis effectively explains primates’ grasping hands adaptation as this allowed them to grasp fruit out of trees with their hands while grasping tree branches with their feet. This hypothesis also explains the shift from insectivory to gumnivory.

One evident issue with this primate evolution hypothesis is that early primates were not the only species consuming fruit in trees and those other species did not develop the same characteristics as primates.