Primates :O

We watched the video on gorillas today in class and I noticed that they moved on all four limbs sometimes, and on their two feet at other times. I also noticed that their arms were longer than their legs.

Questions on how primates move:
- Why do they move on fours sometimes and on their feet at other times?
- Why do they pump/hit the chest?
- Why is there a large space between the first toe and the rest?
- Do gorillas swing on trees? (too heavy?)
- Why is their skin so rough/horny?