Question

Which of the following correctly explains why scientists believe that great apes like chimpanzees and gorillas are more closely related to humans than monkeys on an evolutionary timeline?

Answer 1

We have both morphological and genetic evidence that chimps/gorillas are more closely related to us than monkeys.

Remember that Darwin didn't know about DNA: he based his theories on things like skull shape. If you look at monkey skulls, human skulls, and then gorilla or chimp skulls, you can actually make a table where you list the traits that are present in each species. I did this in one of my classes this semester: it was interesting spending a couple of hours holding real skulls by the eye holes and trying to figure out what they had in common.

A more modern technique is to compare DNA sequences and see where the similarities and differences lie. As it turns out, chimps are 90-something% the same as us genetically. I assume that that number is lower in monkeys.