T-cells are a type of white blood cell that circulate around our bodies, scanning for cellular abnormalities and infections.
They're considered to be human like hands. They have a thumb like humans which allows them to grip onto trees and maneuver better. It also helps them with their grip onto branches and trees because they rarely come down from up there, so they need to be able to grip tightly even a sleep. I would say it's natural selection due to evolution.
