This is a graph of a log of brain mass versus the log of body mass, and one of the things I’d like to show on this diagram is that I’d like to show the relative intelligence of animals on the planet, and in order to do that you can’t just show brain mass, you have to show log mass, or log of the body mass, and I think you can see what I’m talking about when you see of this field.
This is the field for fish, amphibians and reptiles and as you can see for a given body mass, throughout these creatures have a lower brain mass compared to many of the other elements, or I should say animals on our planet.
Well, you’re not going to find any brain surgeons in and among the fish, amphibians and reptiles – that’s for sure.
But where do the mammals fall? The mammals fall at much higher brain mass for a given body mass and that’s because mammals have a neocortex, and that’s what evolved into our grey matter. So it’s not surprising to see that the mammals fall higher than the fish, amphibians and reptiles.
And then the primates, you can see where they fall, they’ve some of the largest brains in the animals’ kingdom and I’m going to talk a little bit more about the primates and explain why they might have gotten those big brains.
But first I want to talk about and concentrate on this red dot. There is a red dot falls to a low body mass and very high brain mass, and that’s where people that come to TED Talks for, but you might like to know. OK.
What we all learn from Jurassic Park that the dinosaurs were geniuses, I mean, think about this, they learn how to open doors, for God’s sake. But I’m here to tell you that they weren’t as smart as we think they were in Jurassic Park was lying to us.
Look where the dinosaurs fall, towards very high body mass but relatively low brain mass. They weren’t the sharpest knives in the door; that’s for sure. Well, now once we get the dinosaurs and we see how they fall, this brings me to an important point, and that is about evolution, and that is evolution doesn’t always select for the brightest creatures.
In the case of the dinosaurs, they were selected for their large body mass, and they were immensely successful. They ruled the planet for 135 million years.
And what were mammals doing during that time?
Well, the mammals first appeared in the Triassic about 200 million years ago. They were little tiny creatures scurrying around trying not to get stepped down by the dinosaurs. And they were that way throughout the entire Mesozoic, and if it weren’t for the demise of the dinosaurs, I’m going to suggest to you that we’ll still be little tiny creatures running around and I wouldn’t be up here talking to you tonight.
And it’s that demise of the dinosaurs that leads me to my second improbable event and that has to do with the destruction of the dinosaurs. These are the Alvarez’s. They’re standing next to what we call the Cretaceous Tertiary boundary. It’s an ash layer, and that ash layer was deposited by – the Alvarez’s discovered this – 66 million years ago by a meteorite impact destruct. It hit Mexico — well, it didn’t hit Mexico.
66 million years ago, Mexico wasn’t there – but get my point – but it hit in that area, and it sent ash to the atmosphere, and that ash was carried around the planet by the atmospheric currents. It caused the planet to be darkened for months, and it stressed the largest animals on the planet, the dinosaurs, that wiped out every one of them and here’s something a lot of people don’t know, it killed off 75% of the species on planet Earth, it was a horrendous event.
Now, where does this statistical improbability come into play here?
Well, think about this. The Alvarez’s discovered that the meteorite was 10 km in diameter, if that meteorite was a little bit bigger than 10 km, it might kill off all life on the planet. And if it’s a little smaller than 10 km, it might not kill off the dinosaur, and we’d still be little tiny creatures.
So I hope you can see the fine-tuning that required here, and the fortuitous event this must have been. Think about it, we have to have just the right size of the meteorite, striking planet Earth in order for us to get here, that seems like a statistically improbable event to me, and I hope it does to you, too.
So what happens after the dinosaurs are gone?
Well, we see the mammals radiated out into all of the niches previously held by the dinosaur. One of the areas that they radiated into are the trees. And the trees are where we get primates. And when you’re jumping around from limb to limb, a lot of the things that are required of that process. There are things that need big brain power, a lot of computing power, so we see the big brain.
Let me give you a couple of examples. The primates have three-dimensional vision. They have color vision, and they have these digits, and it takes a lot of fine motions to move these digits. So it takes immense computing power, and not surprisingly, these things that were selected for in the primates.
Well, they also come within the big brain. And so we see big brains in primates as you saw in that graph I’ve shown earlier.