Evolution Logo

close window

Steven Jay Gould: Understanding Evolution

Transcript:

Q: Why do we humans have a hard time understanding, and sometimes accepting, evolution? What, in your opinion, is the major stumbling block?

A: Deep time is hard to grasp. I don't know that it or any one thing could be called "the" major stumbling block. The major stumbling block is that we're not quite ready, because we live in a veil of tears, and we know that bad things happen to good people. We're still desperate, many of us, to find factual answers out there that would make us feel better in a psychological sense about some of the cruel things that don't make sense in life. And that's a very hard one to get through, I think. Once you come to terms with the recognition that the answers to moral questions aren't out there in nature, and you shouldn't be seeking them there, you have to seek them inside yourself -- and that is the proper role of religion and humanities -- then it ceases to worry. But it does worry many people.

And since it does, there are a whole set of issues that then become very hard to accept, one of which is that most organisms are bacteria. And there isn't a linear progressive pattern that pervades evolution leading up to humans. Another is that humans are a tiny little twig representing one species among so many millions on this enormous arborescent tree of life. And a third is what we're talking about now, that this tiny little twig of Homo sapiens represents an eye blink of geological immensity.

I think they all go together, and they all represent our unwillingness to give up on the notion that there is meaning out there expressed in human terms, which is a kind of ultimate hubris. I don't deny that there's meaning out there that we have to find. But to think that the meaning of this immense complexity and variety of life should be framed only in terms of one funny little primate species to think that it all exists because of us, or that its meaning is framed in terms of us, that's an ultimate kind of arrogance that I think is most unlikely to be correct in any sense.

Q: How does Darwin's theory rank among the great scientific discoveries of all time?

A: Sigmund Freud made a famous and often repeated comment that the few truly great revolutions in the history of science all have the common property that they not only reform our concept of the physical universe -- which obviously they do or we wouldn't call them revolutions -- but that they also ironically knock human arrogance off one pedestal after another of our previous beliefs and our own self importance. And clearly, that's where Darwin ranks so highly.

Freud said that there were really two great revolutions. The first that we associate with Copernicus, Newton, and Galileo that taught us that we weren't living on the central body of a limited universe. And that Darwin's was the second that taught us that we were not separately created in the image of a benevolent deity, but were part of a history of genealogical connectivity of all living things.

Now, in an odd sense, we know how contentious the first revolution was; we know the story of Galileo. But contrary to popular understanding, the church made its peace with Galileo. They may not have taken his books off the index or officially exonerated him until recently. But a few years after his death it was not a hot issue anymore because people knew the earth goes around the sun, and that's all there was to it. And it wasn't going to do much good to try and base a theology on getting nature backwards.

But the way I like to put it, I don't think that revolution was as important as Darwin's, because it's about real estate. The Darwinian revolution is about essence; it's deeper. The Darwinian revolution is about who we are, it's what we're made of, it's what our life means insofar as science can answer that question. Science cannot answer all aspects of that question. It can't tell us what our life means ethically. It can't tell us what we are meant to do as moral creatures. But insofar as science can understand what we're made of, and what we're related to, the Darwinian revolution completely revised our ideas about who we are, and what we're related to, and how long we've been here, and why we're on this earth -- again, in limited ways that science can apprehend or comprehend those questions.

So it, in many ways, was the singularly deepest and most discombobulating of all discoveries that science has ever made. And that it is so factually firm and so well documented merely makes it all the more salient, because it isn't just a conjecture; it's an entire reconstruction of our concept of ourselves and who we are that is as well documented as anything we've ever learned in science. So that does give the Darwinian revolution a unique status.

But, again, we shouldn't take it too far. Science, as any enterprise, has a limited frame. Science is an enterprise that deals with the factual world as we understand it and as we come to understand it better. And it deals with why the factual world works as it does, and not some other way in which it might work. That's roughly fact and theory, but there are many questions about human life and human nature that science can't answer. Science can't answer ethical questions. Science can't answer questions about meaning in the spiritual or theological sense. And we shouldn't pretend that it can.

Q: Can you talk about evolution as an amoral process?

A: I don't think there's moral messages of any kind in nature. The most you can get out of nature is an understanding of how the world operates, which is certainly material you want to factor into any moral debate you're going to have. It's not going to answer moral questions for you.

All that happens in evolution, at least under Darwinian natural selection, is that organisms are struggling in some metaphorical and unconscious sense for differential reproductive success, however it happens. Some succeed; most fail and die. Some succeed by things we don't happen to like, like killing others. Some succeed in it by things we do like, such as cooperation. And others succeed by inflicting enormous pain and harm upon others, including human beings. So we don't like it. But it has nothing to do with nature's ways. If bacterium or a virus gains differential reproduction success by making us sick and exploiting our bodies, then so be it.

Q: How can chance mutations result in adaptations that seem to be purposefully designed?

A: It's a common phrase that natural selection is chance and necessity. It goes back to the title of a book by the great French biologist Jacques Monod. But it's not really correct, because the chance part is not natural selection. Natural selection is actually a locally deterministic force.

If you want to say the Darwinian evolution has a component of chance, and a component of local necessity, that's quite accurate. But the basic argument goes like this: Because natural selection doesn't make anything, natural selection is an eliminative force. Natural selection can only differentially preserve certain variations in a spectrum of variation within a species. Now some other process produces that variation; ultimately it's mutation. And mutation is spread around through recombination and sexual organisms.

But because the causes of genetic mutation are occurring at the level of the gene, and bear no reference to the adaptive design of organisms, the variation among the organisms produced by mutation bears no relationship to what's for the good of organisms. So it's not random in the mathematical sense of flipping a coin and getting 50-50 [chance]. All we mean is that the variation which provides the fuel for natural selection occurs without reference to those characteristics that would be useful for an organism.

For example, if you have a bunch of elephants living in Siberia, and it's getting cold because there's an ice sheet advancing, there's going to be another Ice Age, you're going to have elephants with different amounts of hair on their bodies. But there isn't any internal force that produces more hair because that would be a good thing. You just have variation among these different elephants, and that's what we call random with respect to the direction of natural selection. And then you have the second force, which is natural selection, which is not necessity or determinism on a global scale. Natural selection doesn't make overall more progressive or better organisms; natural selection makes locally adapted organisms.

If you go back to that analogy, if you have a bunch of elephants and it's getting colder, on average, -- this is statistical phenomenon, not every time. After all, the hairiest elephant can fall into a crevasse and die or be sterile and have no kids. But it's a statistical phenomenon that elephants with more hair are going to leave more surviving offspring. And that's natural selection.

Q: Do scientists and the lay public sometimes misunderstand each other around evolution as conjecture, or around how much is really known?

A: Scientists and the lay public often misunderstand each other in the same sense that people who have deep technical knowledge about any subject tend not to talk about it very well to lay people. They often get into confusions. But I don't know that it's any worse for science than for others. There is obviously a particular context, because in the United States -- uniquely in the Western world, I might add -- there is a politically motivated bunch of folks out there who have a certain amount of local power, even though they keep losing court cases, who for their own political reasons are trying to push anti-evolutionism.

But putting that aside -- which has very little to do with the content of science, though it's an interesting sociopolitical issue in American history -- I don't know what to say, except that as a factual proposition, evolution is about as well-documented as anything we know very broadly in science; that there is a tree of life, that all organisms are tied by genealogical connectivity, that the history of life is, to use Darwin's words, "descent with modification." I would say that's as well known as that the earth goes around the sun, and not vice-versa.

Now there are all number of details that we don't know, because you're dealing with an enormously complex narrative history of life that often doesn't leave evidence of particular highways and byways. Just as I can't give you a list of every soldier who fought at the Battle of Marathon, but I don't doubt there was such a battle, I can't tell you every species of brachiopod that died out in the Permian extinction, but I can be pretty confident that large numbers of them did.

So I think we're very confident about the basic factuality of evolution. But there's so much we don't know about particulars of detailed pathways, and there's a lot we need to learn about mechanisms. But that's true of all science. Science is a continually self-correcting enterprise that doesn't always move triumphantly forward, but somehow works its way to a better understanding of a pretty complex factual reality out there.

Q: How much do we owe who we are today, our bodies and our beings, to the 4 billion year history of environments and environmental change?

A: Evolution is the only process behind the construction of our bodies, in a biological sense. Clearly all the sciences are involved. The periodic table explains the elements that we're made out of. Physics gets to the particles. But if you want to talk about the history of life, that subject is evolution, the distinctive characteristics of this one funny little primate species that is us, or a function of that history. So evolutionary biology is the right subject to consult.

We're basically a pretty ordinary mammal, with one absolutely stunningly remarkable and powerful invention -- what we call, for better or worse, "consciousness." But it's important not to mistake the power of that invention, which is undoubted -- I don't think anything else has ever happened in the history of evolution that has so quickly given one funny little species such power over a planet or over other living things. But you mustn't confuse the impact of something with its fundamental mystery. It still remains an aspect of evolutionary history that consciousness enables us to do all sorts of things that were not anticipated or not part of the actual reason why it all happened. It just adds to the interest. But there it is.

Q: How do you help students understand the importance of the earth's history and changing environments to evolution?

A: The basic theory of natural selection talks not about predictable universal progress, or any inherent direction of evolution. It's only a theory of adaptation to changing local environments. That's really all it is. The parasite that becomes morphologically simplified, living inside the body of its host, is as well adapted to its environment as the complex bird flying through the air. That's all it is: a theory of adaptation to changing local environments.

Now because the history of the earth, its four-and-a-half billion years, is a story of environmental change -- a story of mountains building and seas moving in and out, and ice ages coming and going -- the story of life history, insofar as it's regulated by natural history, is a constant interplay and dance back and forth. Environments change; creatures change to match those environments.

It's not an automatic, mechanical process. Because by environment we just don't mean it gets colder and an animal gets hair. Environment is a complex construction that includes the other organisms that share it with you. When you adapt to your environment, that environment isn't only the climate and the mountains and the oceans; it's also the other organisms in that world.

In the same sense that human history is wonderfully complex and unpredictable, because you never know when the next river is going to break through, the next army is going to invade, the history of life is the same way. It's a constant process of adaptation by natural selection to changing local environments. And the vector of those environmental changes through time is effectively random. That makes the history of life itself unpredictable, but still eminently documentable.

© 2001   WGBH Educational Foundation and Clear Blue Sky Productions, inc. All rights reserved.