Ask Glenn

If we evolved from chimps and gorillas, why do we still have chimps and gorillas?

Firstly, we didn’t evolve from chimps and gorillas – we just share some great-great-great-greatgrandparents with them. Secondly, chimps and gorillas are doing fine as they are (at least for now) so why should they need to evolve any more?

But I’m sure I saw it in a book! There was this chimp, and then a caveman, and then a guy with a beard...

Unfortunately, that’s not quite how it works. Many books show evolution like this – as if it’s a race won by humans, or a ladder with humans at the top. But it’s really not.

Why not?

Because if it were a race, then we didn’t win, and if it were a ladder, then chimps and gorillas are standing at the top alongside us. We all evolved from a common ancestor, but we didn’t replace chimps and gorillas. In fact, we evolved alongside them.

Eh? I don’t get it.

Try this. Imagine there’s a huge line of people doing that silly ‘conga’ dance where everyone holds on to the hips of the person in front. Now imagine you’re at the front, and behind you is your dad. Behind your dad is his father (or your grandad) and behind him is his father, and so on.

Chimps evolving into man, evolving into little boy

OK...

Now as you go back down the line, you’d see your ancestors trail back into time, until eventually you get to ‘cavemen’, or early humans like homo erectus, homo habilis and others. They’d be a bit shorter and hairier than your dad and granddad, with more sticky-out facial features, but otherwise not too different. Some way behind them would be something that looked a bit (but not exactly) like a chimpanzee. He’d be short, hairy, and would walk using both his feet and the knuckles of his hands (at least he would if he wasn’t already doing the conga). How far do you think the line would stretch between you and this creature?

I don’t know. Thousands? Millions?

Only about 300 miles.

No way!

Yep, only about 300 miles between you and the ancestor we share with chimpanzees. But it wasn’t actually a chimp. It was the animal that – if he started a second conga line by holding on to his other son – would eventually lead to a modern chimp. If the two lines conga’d side by side, and you walked along them from the back to the front, then dancers level which each other would look more and more different as you went up the line. Until, eventually, you’d arrive at your dad and a chimp waiting side by side at the front of the lines.

So evolution is more like a pair of ladders, then?

It’s more like thousands of ladders – one for each species alive today. But since they all join up at the bottom (with another shared ancestor further back), it’s probably easier to think of evolution like a huge tree, with the first living thing at the base or trunk, and thousands of branches leading to everything alive today. Or a single river that splits into thousands of smaller streams. If you think of it like this, then some streams – like those that lead to tyrannosaurs and dodos – dry up into the earth, while others survive and flow into the future.

So we still have gorillas and chimps because...

...because they, we and all the other species alive today have survived the test of time. Whereas tyrannosaurs and dodos have not.

Shame.

Yes, it is. But, then again, there wouldn’t be many people around if the world was full of tyrannosaurs!