Q: What are memes?
A: Certainly, when we look around us and are amazed at all the things that Homo sapiens has wrought -- rockets that go to the moon and the Internet and modern medicine and so on -- that wasn't because our brain evolved to do those things in particular; no Robinson Crusoe thinking by himself on a desert island could have invented a rocket. It depends on the accumulation of an enormous number of discoveries that were passed on, not through the genes, but from one person to another through language and other forms of communication.
This is called cultural evolution. Some people call the units of cultural evolution memes -- little units of memory or knowledge -- and we've been accumulating them for tens of thousands of years.
So we figured out how to make nice sharp tools and our jaws and teeth became smaller. We figured out how to use the hides of other animals to stay warm and we got naked. We are now figuring out how to cure diseases, how to build shelters. And for tens of thousands of years the products of the human brain have accumulated in almost a parallel course in evolution to the changes in our bodies and brains.
These memes can be anything from styles that help you fit into a group, like turning a baseball cap around and wearing the peak in the back, to figuring out the cure for some disease or how to grow crops. So the products of the brain that have been transmitted not through the brains but through language have, for many thousands of years, been as important or more important than the actual physical stuff that we're made out of.
A lot of the creations of our brain can make up for physical deficiencies, and could actually change the course of evolution. Thousands of years ago, someone who was severely nearsighted probably wouldn't have had many descendants; he would have been eaten or fallen off a cliff a long time ago. But we invented eyeglasses and now being nearsighted has no disadvantage at all.
There are some people who might say, "Well, isn't this interfering with evolution? Wouldn't we be better off letting the diabetics and the nearsighted die an early death to improve the physical vigor of the species?" That really goes against the way that human evolution works, which is that for tens of thousands of years we've depended for our survival on our own inventions, on our own creation, and this is simply extending this process.
Also, probably the longer we look the more we'll find evidence for signs of human creativity and ingenuity in Africa. Europe is where you have a lot of caves, which preserve stuff, and Europe is where you have a lot of archaeologists out looking for human remains, and so I think there's a bit of a bias toward the European landscape. As people get cleverer about finding things in Africa and look longer, I suspect that we will see things beyond the age at which the European artifacts appear.
We also know that a lot of our evolution had to have taken place before the human races diverge because we're pretty much birds of a feather. If you took a bunch of human babies from anywhere around the world -- from Australia, New Guinea, Africa, Europe -- and scrambled the babies at birth and brought them up in any society, they'd all be able to learn the same languages, learn how to count, learn how to use computers, learn how to make and use tools. It suggests that the distinctively human parts of our intelligence were in place before our ancestors split off into the different continents.
Q: So what happened fifty thousand years ago?
A: Human evolution, at first, seems extraordinary. How could the process that gave rise to slugs and oak trees and fish produce a creature that can fly to the moon and invent the Internet and cross the ocean in boats? Was it some kind of divine spark that made our brains special? Well, I don't think so, because I think that you can understand human evolution in terms of the ordinary process of Darwinian natural selection.
The way to understand how different species evolved is to think about the niches that they fill in an ecosystem -- basically, how they make a living. And how do humans make a living? Well, with their brains. You could think of an ecosystem as a bunch of antagonistic arms races, almost: Everything that an animal depends upon for food is the body part of some other animal or plant who would just as soon keep that body part for itself.
And so all the things that we depend on for food evolve defenses against being eaten. Animals run away, they develop spines or poisons. Plants can't very well defend themselves by their behavior, so they resort to chemical warfare, and plants are saturated with toxins and irritants to deter creatures like us who want to eat them. Now, whenever you have some kind of defensive weapon in nature, you get an offensive weapon, and vice versa. So as the hide gets thicker, the fangs get stronger and sharper, which makes the hides get thicker still, and so on.
This arms race, though, is played out in evolutionary time, and the animal can't will its skin to get thicker in its own lifetime. Now, here's the trick, I think, behind humans: We participate in this arms race -- but in our own lifetime, not in evolutionary time -- by using our brains, by developing a model of how the world works, what causes lead to what effects, and figuring out ways of defeating the defenses of other plants and animals before they can evolve countermeasures in response.
So we invent snares or camouflaged pits, or we coordinate our behavior to drive large animals and stampede them over a cliff, or ways of detoxifying plants by cooking them or fermenting them or soaking them. And because we can figure these things out in our mind's eye by learning how the world works, we can figure out how to use more of the ecosystem to our advantage, and I think that explains why these big-brained creatures became as successful over the planet as they did.
Q: How did evolution, for humans, happen so quickly? We [already] had a big brain, but how did the big brain suddenly start working?
A: Certainly humans didn't evolve to their present state in one instant, in one fell swoop, because we know that our ancestors, the species like Homo erectus and Homo habilis already had a pretty big brain for a primate of that size. They were already using tools. They were almost certainly cooperating with one another. So it's not as if our species was the first to do it; it was building on some earlier stepping stones.
And it's unlikely that it happened all at once. You have to remember that not every creature that was evolving left behind its skull or its tools for our convenience tens of thousands of years later. Most bones or most tools rot or get buried and are never found again. So the earliest date at which we find some fossil or artifact is not the point at which the species first appeared; it was probably doing its thing for many tens of thousands of years before we were lucky enough to find something that it left behind that lasted to the present day.
Q: Can you talk about the rewiring of the human brain?
A: You have to remember that human intelligence and intelligent behavior don't just come from having a whole bunch of stuff packed into our skull like meatloaf. The actual organization of behavior goes on the level of the individual nerve cells and their connections, and we have a hundred billion nerve cells, probably a hundred trillion connections. It's just mind-boggling to think of all the different ways in which they're arranged in a baby's head. And a lot of our evolution consisted not just in getting more of this stuff, but in wiring it in precise ways to support intelligence.
Q: Does Darwinian evolution allow for such internal rewiring as part of its process?
A: There are lots of ways in which Darwinian natural selection could rewire a brain. There are chemicals that are released in the growing brain that attract nerve cells, encouraging them to grow in certain pathways versus others. There are molecules at the tips of the growing neurons that can engage or not engage some target, like a lock and a key. There are rules for when brain cells die in what part of the brain, so that they might grow in one part, die off in another. All of these are under the control of genes, and as genes evolve, the way they do throughout evolution, the wiring of the brain can change.
Q: So this rewiring pattern happened progressively?
A: Yes. It's very likely that the changes in the brain didn't happen overnight. There wasn't one magical mutation that miraculously allowed us to speak and to walk upright and to cooperate with one another and to figure out how the world works; evolution doesn't work that way. It would be staggeringly improbable for one mutation to do all that. Chances are there were lots and lots of mutations over a span of tens, maybe even hundreds of thousands of years, that fine-tuned and sculpted the brain to give it all the magnificent powers that it has today.
I don't think there was a thunderclap or a divine spark that suddenly made one species smart. You can see, in our ancestors, there was a gradual expansion of the brain, there was an expansion of the complexity of tools. Even when our species evolved, it surely was spread out over tens of thousands of years. The fact that we find a whole bunch of artwork or tools in one place just means that that's when they arrived there and left some garbage that survived to the present time. But it's virtually certain that it was extended over many, many generations before that.
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