Yesterday I posted something on Facebook about the lack of knowledge some people seem to have about evolution. I want to keep this blog very tight in its content, because it's very easy for this topic to derail (as happened on FB). I am not discussing anything more than a process here.
The point in question is the chestnut "If we come from monkeys, why are there still monkeys."
Firstly, we don't come from monkeys, and nobody ever said we did. So the question is disingenuous before it begins. I don't know quite how this misunderstanding arose but it stuck.
The correct version is that monkeys and humans share a common ancestor. For the sake of this discussion, we shall call them our cousins, using a very broad and non-scientific definition of the word cousin. I want you to think of your own cousin, who we'll assume is called Fred.
You and Fred are cousins. You have a common ancestor, your grandfather Bob. Bob is still alive. He hasn't gone anywhere. Fred is still here, and so are you. Two people can share a grandparent. It does not kill the grandparent. Moreover the grandparent doesn't change.
You and Fred both look a bit like Bob, but you are not Bob. You have another grandfather, Sid, and Fred has another grandfather, Hank. So, you also look a bit like Sid, and Fred looks a bit like Hank. That's why you and Fred look different.
This is all obvious and quite reasonable. You knew it all before and it comes as no surprise to you.
So, you come from Bob, but there is still a Bob. Fred comes from Bob, and there is still a Bob. And you and Fred both exist. At the same time. You know this.
You may even know that the reason you look a bit like Bob and a bit like Sid is because of DNA. DNA is how a human baby knows what to look like. It's a sort of blueprint.
DNA is in all living things. It doesn't vary as much as you might think. Look at your dog. He's nothing like you, but he has a skeleton, eyes, teeth, lungs, and everything else you have. His DNA is different to yours, so when he was a puppy his body knew what shape to make him. But it's not different enough to make him look like a banana. Bananas have DNA that is more different.
When you look at a monkey, its DNA is not very different to yours at all. Because you are reasonably close cousins. Not at close as Fred, not by a long shot, but closer than your dog, and much closer than a banana.
The monkey's great-great-great-grandfather didn't look much like him. But he looked more like him than a banana. Your great-great-great-grandfather didn't look much like you, but he looked more like you than a banana. That's because the monkey's great-great-great-grandfather and your great-great-great-grandfather had much more similar DNA.
If you keep going back, many, many grandfathers, they looked less and less like you. But let's look at it the other way around.
I'm sure you know, almost all modern breeds of dogs come from one or two early dogs, the wolf being the most important one. A dog is not a wolf, but many grandfathers ago, there was a wolf. Your dog may be a German Shepherd, which looks quite similar to a wolf, or he may be a Scottish Terrier, which doesn't. But both of them have a common ancestor, a wolf.
Why is a dog not a wolf? Because it stoped being a wolf a long time ago. When? Difficult to say, but within the last 4,000 years. At which point was it not a wolf or a dog, but a sort of dogwolf or wolfdog? That didn't happen just once. It happened a number of time, and over many generations. It is still happening, in many cases. Some dogs are definitely dogs. Some are still obviously quite wolfy. The separation is not complete.
This is evolution, happening. Now. You are watching it happen. Sorry it's so slow. It's been happening about 4,000 years and who knows how much longer.
It hasn't stopped because you can still breed a wolf to a dog. They are different in many ways, but they can interbreed. So they are not quite entirely different.
And when, in maybe another 4,000 years times, they will no longer be able to interbreed, there will still be dogs and there will still be wolves - provided we haven't killed them all off.
The separation into two new groups, which we just happen to refer to as species, doesn't happen overnight, doesn't happen in one place at one time, and doesn't do any harm to the original group. It may become extinct anyway, for some other reason, but not directly because of this.
The change from wolf to dog happened because humans got involved. That's doesn't disqualify it from being evolution. Plenty of examples of outside influences cause evolutionary processes to occur, and they can be quite fast. A storm in the Pacific can cause a flock of birds to fly off course and settle on a new island. If the food there is different, the birds will evolve to cope with that, and soon look quite different to their "cousins" - who still exist - on the old island.
How quickly? If it only takes 4,000 years to get a Scottish Terrier from a wolf, it doesn't take long for a bird's beak to grow or shorter, for his legs or body to get bigger or smaller, or whatever. It happens in incremental steps over generations, and there are plenty of those.
A human can be several inches shorter or taller than his father. That's a variation possible in just one generation. Birds aren't quite that variable in one generation, but if there were an evolutionary advantage to a bird having longer legs, it wouldn't take many generations for it to become the norm.
But 4,000 years is nothing. No time at all. A blip. There have been millions of years for this to happen. If there is an evolutionary advantage to be taller, the generations only need to increase in size by tiny amounts for them to grow very large after many years. Even if the increase in size wasn't steady, 2 steps forward and 1 step back, how many generations would it take for the whole population to grow 6 inches taller?
This has actually happened to humans, and quite quickly. In medieval times the average man was much shorter than today. We still get short men though. They haven't been wiped out as a result of the average height increasing.
Development in evolution does not result in the original population disappearing. Is this not clear enough?
Suppose you have a box of 12 eggs. You take 6 and bake a cake. The other 6 are still there. It's really that simple.
I have tried to make this as simple as possible. I will answer questions, publically or privately on this issue. For the sake of clarity, if you wish to discuss another aspect of this debate, we'll do that separately. But if you still don't understand how we can have both humans and monkeys, I will be patient with you, as long as it takes, to help you understand. You can contact me at firstname.lastname@example.org.