I just led a Great Ape safari through Uganda and Rwanda to see chimps, gorillas and many other primates. It was a thrill to look into the feisty eyes or a chimp and the calm brown eyes of a gorilla and feel the connection – kin – but not quite. I was especially aware of our differences because one of my guests had said at the beginning of the safari:
“I came on this trip in order to see our closest ancestors.”
“No.” I had to reply. “None of the great apes alive today are our ancestors. Our ape ancestors have been dead for over 6 million years.”
He looked puzzled but eager to understand. So let’s try to make it clear how we are related. First, we humans and all the monkeys and apes are primates. Primates are an order of mammals with binocular and color vision and grasping hands. Primates split off from the ancestral mammals about 60 million years ago and diverged into various kinds. Through fossils and DNA we can trace the ape line back about 25 to 30 million years. The “ancestral ape” had no tail and was larger and longer-lived than other primates.
The apes continued to split; gibbons and orangutans went their own special ways and the other ape line kept evolving too. By about 9 million years ago a gorilla line was established and the rest of the ape-like beings evolved into two major types: chimps and hominins. Today we have two living representatives of the chimp line – chimpanzees and bonobos. Since Neanderthals died out relatively recently, that leaves only humans as representatives of our hominin line – the upright walking apes. So apes are our relatives but NOT our ancestors.
Here is a family tree with the living apes that shows the very approximate times when we left the other primates. A family tree is like an African flat-topped acacia, whose gnarled branches separated long ago and all the little twigs of the canopy have been on earth for the same amount of time. We humans are not at the top of a tree like a pine, with all other creatures down below us. I think it is very important to realize that all living beings are at the same level, we are all survivors through time. Gorillas and chimps are definitely our surviving relatives, but not ancestors.