Prime Time Replay:
William Calvin
on the evolution of the brain
MsgId: *breakthrough(1)
Date: Wed Dec 17 19:25:39 PST 1997
From: moderator At: 152.163.213.218
Hi, I'm your moderator, Madeleine Lebwohl, and tonight I'll be speaking with William Calvin, a theoretical neurophysiologist at the University of Washington in Seattle.Tonight our chat will be an in-studio interview. Welcome, Dr. Calvin.
MsgId: *breakthrough(3)
Date: Wed Dec 17 19:26:56 PST 1997
From: moderator At: 152.163.213.218
Dr. Calvin: Hello to everyone.
MsgId: *breakthrough(4)
Date: Wed Dec 17 19:29:44 PST 1997
From: moderator At: 152.163.213.218
Last year you came out with two books, "The Cerebral Code" and "How Brains Think." They cover how we think today, and how we got here. What kind of a reaction have you gotten from them?
MsgId: *breakthrough(5)
Date: Wed Dec 17 19:31:58 PST 1997
From: moderator At: 152.163.213.218
Dr. Calvin: They're two very different books. "The Cerebral Code" is about the brain circuitry, to think something you've never thought before, a Darwinian process on the time scale of thought and action. "How Brains Think" is about both the ice ages and thought in action and the application of thought in action. Its a book in the Science Masters Series.
MsgId: *breakthrough(6)
Date: Wed Dec 17 19:33:10 PST 1997
From: moderator At: 152.163.213.218
As the structure of the brain goes, do you still anticipate changes happening?
MsgId: *breakthrough(7)
Date: Wed Dec 17 19:34:36 PST 1997
From: moderator At: 152.163.213.218
Dr. Calvin: No. Brains reached their current size before the last ice age started, and didn't change all through it. And I doubt it will change again because of agriculture. Natural selection is not what it used to be.
MsgId: *breakthrough(8)
Date: Wed Dec 17 19:35:54 PST 1997
From: moderator At: 152.163.213.218
When new technology comes along, and people have to learn how to use it, is that without effect on the brain? Are we left the same?
MsgId: *breakthrough(9)
Date: Wed Dec 17 19:39:22 PST 1997
From: moderator At: 152.163.213.218
Dr. Calvin: Its not clear that bigger brains are better. Its not at all clear what has made brains bigger. But the ice ages are mostly what we owe our big brains to. We had ape size brains up until two and a half million years ago. Our ancestors split off from the chimpanzees about five million ago, and we started walking upright, but our brain size didn't change, not until the ice ages started, then the brain size increased four times over two and a half million years. But not, interestingly enough, during the very last ice age, of the last hundred and twenty-five thousand years.
MsgId: *breakthrough(10)
Date: Wed Dec 17 19:40:45 PST 1997
From: moderator At: 152.163.213.218
Why does brain size only change during the ice ages?
MsgId: *breakthrough(11)
Date: Wed Dec 17 19:44:31 PST 1997
From: moderator At: 152.163.213.218
Dr. Calvin: Well, that's been a puzzle for twenty years. Our ancestors were living down in equatorial Africa, where there wasn't much ice, and there wasn't even winter time. My guess is that it was the abrupt climate changes that did it, a flicker between warming and cooling that's been recently discovered. For several centuries temperature may suddenly cool abruptly, and then suddenly warm back up. This plays havoc with whatever way you're trying to make your living. Whatever your parents taught you doesn't work all of a sudden. So its not the ice, its the resources changing. You have to discover a new way of making a living and do it very quickly, you know, just within five years. Just during the last ice age, which started about a hundred and seventeen thousand years ago, there were dozens of these abrupt temperature changes, either sudden warming or sudden cooling by five or ten degrees. And they affected people just like us. Modern type homo sapiens was around just before the last ice age started.
MsgId: *breakthrough(13)
Date: Wed Dec 17 19:47:57 PST 1997
From: moderator At: 152.163.213.218
What was the mechanism of this sudden change?
MsgId: *breakthrough(14)
Date: Wed Dec 17 19:51:39 PST 1997
From: moderator At: 152.163.213.218
Dr. Calvin: The answer to that is in the January issue of the Atlantic Monthly. My article, "The Great Climate Flip-Flop," doesn't have very much about brains in it, but I review what the paleoclimatologists and the oceanographers have been discovering over the last fifteen years. Basically, what the Europeans called the 'Gulf Stream' has several modes of operation. The present mode of operation, seen during warm periods like today, carries equatorial heat far north, all the way up the coast to Norway, and west around the tip of Greenland. During the abrupt coolings something appears to happen to this, its something like a bus route that goes out from the center of the city into the county, except during a snow emergency when it turns around at the city limit and comes back.That shortening of the loop is what causes the snow emergency in this case, an abrupt cooling, if maintained for a very long time, causes an ice age. But usually it only lasts for a few centuries, and then abruptly changes back into the old mode. It shows you that climate change doesn't have to be gradual, it can be very quick. And dozens of these abrupt flips occured in the last hundred and seventeen thousand years. They even occur during warm periods like today's. And abrupt coolings are what also end warm periods. Warm periods do not end gradually.
MsgId: *breakthrough(16)
Date: Wed Dec 17 19:55:26 PST 1997
From: moderator At: 152.163.213.218
What causes one of these cold flips to occur?
MsgId: *breakthrough(17)
Date: Wed Dec 17 19:58:40 PST 1997
From: moderator At: 152.163.213.218
Dr. Calvin: The oceanographers think they know, and I'm very persuaded by their arguments. Fundamentally the problem is getting rid of the gulf stream water once its given up its heat. All ocean currents have to travel in complete loops, but the North Atlantic is unusual in that the loop is vertical. The surface water sinks to the bottom of the ocean every winter, and then flows southward. This makes room for more warm water to flow north from the equator, and that's fundamentally why Europe is much warmer than Canada. However, this sinking of the surface water can be stopped by enough rainfall in the ocean, or by enough ice melting, and layering fresh water onto the ocean surface. That keeps the cold water from sinking, and stops the additional warm water from flowing north.The big worry at the moment is that global warming may trip one of these flips, that we could paradoxically get an abrupt cooling as a response to our warming trend. It can both melt the ice in Greenland and it can cause more rainfall in the North Atlantic. Either way, this 'nordic seas heat pump' can be halted.
MsgId: *breakthrough(19)
Date: Wed Dec 17 20:02:12 PST 1997
From: moderator At: 152.163.213.218
How soon will we know if we could be causing one of these flips?
MsgId: *breakthrough(20)
Date: Wed Dec 17 20:04:22 PST 1997
From: moderator At: 152.163.213.218
Dr. Calvin: Its not something that you can do much about once it starts, but you may be able to prevent it. The current state of affairs is that the oceanographers are very worried about this sinking of the surface waters at present. In the Labrador Sea, between Greenland and Canada, flushing of the surface waters failed during the 1970's. It was strong again by 1990 and its declining again. In the Greenland Sea north of Iceland, the surface flushing declined by 80% during the decade of the 1980's. Now the records don't go back far enough to know whether these are just fluctuations or a serious trend, but the current state of affairs is not very reassuring.Basically what we have to worry about is some more ordinary short term climate fluctuation, like El Nino, tripping the flip. We're actually experiencing two major short term climate changes at the moment. Besides the current El Nino, we've also experiencing an episode of the North Atlantic osillation, which is why Europe is having droughts and cold winters for the last several years. It also decreases the flushing of the cold surface waters in the late winter.
MsgId: *breakthrough(23)
Date: Wed Dec 17 20:11:25 PST 1997
From: moderator At: 152.163.213.218
Getting back to the mechanism of brains getting bigger, how did it happen? What triggered it?
MsgId: *breakthrough(24)
Date: Wed Dec 17 20:15:14 PST 1997
From: moderator At: 152.163.213.218
Dr. Calvin: Whenever one of these cold flips happened to our ancestors, they usually had to find different food than what they'd been relying upon. If they'd been hunting, the game animals would probably dissapear, and they'd have to quickly rediscover eating things like roots. Basically, evolution is normally thought to be about efficiency, but when you have abrupt climate changes, then a jack of all trades can do much better. And I think that there has been many hundreds of episodes like these to conserve the individuals with versatility, at the same time that the pure specialists would die out. I still don't know what this has to do with brain size as such, but its the best guess at the moment. There's a few chapters about this in "How Brains Think."
MsgId: *breakthrough(25)
Date: Wed Dec 17 20:16:15 PST 1997
From: moderator At: 152.163.213.218
Why was it only human brains that got bigger?
MsgId: *breakthrough(26)
Date: Wed Dec 17 20:19:06 PST 1997
From: moderator At: 152.163.213.218
Dr. Calvin: That's a very good question and I don't know the answer to it. One would expect bears, for example, to have been affected something like we were. Bears are omnivores, too. But bears have different way of getting through the winter than we do. They can hibernate when resources are poor. The real problem as I see it, is winter time. If you live in a place where the plants go dormant and the ground goes frozen for several months, you either need to be able to eat grass, or to eat an animal that eats grass. My guesses are that our ancestors learned how to hunt well enough to get through the winter time.
MsgId: *breakthrough(27)
Date: Wed Dec 17 20:20:29 PST 1997
From: moderator At: 152.163.213.218
The same way that only humans brains got bigger, only humans have developed language. Any thoughts on why?
MsgId: *breakthrough(28)
Date: Wed Dec 17 20:23:29 PST 1997
From: moderator At: 152.163.213.218
Dr. Calvin: My guess is that all the higher brain functions share some common brain mechanisms. Language, planning ahead, music, and logical trains of thought, and games with rules, they all involve novel sequences of parts. So do some more lowly functions, such as hammering and throwing. My guess is that if you make improvements in any one of these that you improve the others as well. My guess is that in some millennia, hunting skills rewarded any variance in these brain mechanisms, and in other millennia, languages advantages might have done so. I doubt that music played much of a role in this. It may be the original free lunch.
MsgId: *breakthrough(29)
Date: Wed Dec 17 20:24:59 PST 1997
From: moderator At: 152.163.213.218
Did the need to safeguard and improve reproduction or longevity have any part in increasing brain size?
MsgId: *breakthrough(30)
Date: Wed Dec 17 20:27:22 PST 1997
From: moderator At: 152.163.213.218
Dr. Calvin: Yes, but that's true of any aspect of evolution. Basically, most natural selection affects juveniles. Babies simply don't grow up in most societies, on average. Its getting through the episodes of childhood diseases and poor diet that gets kids up to reproductive age, and most of them don't make it. Once people are up to reproductive age, sexual selection starts to become much more important, and environmental selection. I doubt that longevity, per se, plays much role in this at all.Language, for example, may be important for sexual selection. In societies where females chose their mates, they may very well be influenced by the male's language abilities. Finding food is very important for getting juveniles through the dangerous years. In most ape societies and primates in general, this is the mother's job. Sometime in hominid evolution, the mating system changed somewhat. Human males help feed their own offspring, but you don't see anything of this sort in the apes. There are a whole complex of factors involved in what made humans out of apes: hunting, language, pair bonding, and plan ahead abilities, are the most important ones to my way of thinking. And a climate that suddenly flips back and forth does mean that the versatile survive better.
MsgId: *breakthrough(32)
Date: Wed Dec 17 20:33:53 PST 1997
From: moderator At: 152.163.213.218
What the mechanism that changed ape language into human language?
MsgId: *breakthrough(33)
Date: Wed Dec 17 20:37:18 PST 1997
From: moderator At: 152.163.213.218
Dr. Calvin: Well, first of all apes don't have a language. They do a lot better than the monkeys that have perhaps a half dozen cries and calls. Chimps have about thirty six. But several of them used in combination don't have a third meaning. They're not words in our sense of the word. They're much more like our emotional utterances and swear words. The question of how we got words from that and how words became modern human languages is not a settled issue. I've been working on this problem with a linguist, Derek Bickurton, who says that there's an intermediate level called protolanguage. Protolanguage is what kids speak who are less than two years old. And what some brain damaged individuals revert to in aphasia.In a protolanguage, utterances aren't very long, just three or four words. They don't have any structure, like phrases or clauses, and you don't need structure when there are so few words that you can guess their relationship to one another. But by the age of three kids have learned about language structure, just from listening to it, and structure means that you can create very long utterances. I can even say,'I think I saw him leave to go home.' Which has four verbs. Such nested embedding goes far beyond protolanguage, and ape utterances.
MsgId: *breakthrough(35)
Date: Wed Dec 17 20:41:20 PST 1997
From: moderator At: 152.163.213.218
Are apes incapable of doing that?
MsgId: *breakthrough(36)
Date: Wed Dec 17 20:44:03 PST 1997
From: moderator At: 152.163.213.218
Dr. Calvin: In the wild, they don't do it. But with tutoring, they can do protolanguage. They can understand it much better than they can produce it. Kanzi, the Bonobo, who has a dozen years of language tutoring, can understand sentences he's never heard before, about as well as a two and a half year old child. But he doesn't generate sentences of more than two or three words. And that doesn't require any structure. But clearly apes have a great deal of language capability that they don't use in the wild.
MsgId: *breakthrough(37)
Date: Wed Dec 17 20:44:44 PST 1997
From: moderator At: 152.163.213.218
Do you think humans have similar latent abilities in their brains that aren't being used yet?
MsgId: *breakthrough(38)
Date: Wed Dec 17 20:48:22 PST 1997
From: moderator At: 152.163.213.218
Dr. Calvin: Surely, we do. We had a latent ability to drive cars in heavy traffic that was never used until recently. Our abilities to read and write weren't used until about five thousand years ago. It just reminds you that there's a lot of spare time use of brain mechanisms, that circuitry originally used for one thing can be later used for other things. I suspect, for example, that the brain circuitry for accurate throwing can be used for planning on a time scale of weeks and years, and certainly for planning what sentence to speak next. Even though the natural selection that earned it was on the time scale of' get set and throw.'
MsgId: *breakthrough(39)
Date: Wed Dec 17 20:49:58 PST 1997
From: moderator At: 152.163.213.218
Humans plan ahead, but we don't see apes planning for the next decade. What goes into that?
MsgId: *breakthrough(40)
Date: Wed Dec 17 20:53:25 PST 1997
From: moderator At: 152.163.213.218
Dr. Calvin: Our foresight is an amazing thing. It makes possible our ethical behavior, to be able to imagine what a proposed course of action might do to someone else, and our abilities to guess the future often enable us to head off trouble. The biggest challenge in that regard, is heading off another abrupt climate change. As I said in the closing pages of my Atlantic Monthly article, we may be able to stabilize the abrupt change aspects of climate. Probably not El Nino, but we might be able to stabilize the flip-flop tendencies.
MsgId: *breakthrough(41)
Date: Wed Dec 17 20:54:14 PST 1997
From: moderator At: 152.163.213.218
Thank you for joining me on Breakthrough Medicine.
MsgId: *breakthrough(42)
Date: Wed Dec 17 20:54:43 PST 1997
From: moderator At: 152.163.213.218
Dr. Calvin: Goodbye.
MsgId: *breakthrough(43)
Date: Wed Dec 17 20:58:38 PST 1997
From: moderator At: 152.163.213.218
Please join me next week when I speak with Christopher Wills, author of "Yellow Fever, Black Goddess: The Coevolution of People and Plagues."
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