JUDY WOODRUFF: Next, the legacy of Charles Darwin. People around the world have been celebrating the 200th anniversary of his birth this week. Jeffrey Brown has our Science Unit look at his influence all these years later.
JEFFREY BROWN: In 1831, a young naturalist named Charles Darwin embarked on a five-year journey to South America and the Galapagos Islands. What Darwin found in the specimens he collected there would make him the most celebrated scientist of his time and fundamentally change our understanding of how life on Earth develops.
Darwin’s “On the Origin of Species” was published 150 years ago, and the world is now marking the 200th birthday of the man himself.
We talk about Darwin and his legacy now with David Quammen, a science writer and author of the biography “The Reluctant Mr. Darwin,” and Ken Miller, a professor of biology at Brown University and one of the NewsHour’s science advisers.
David Quammen, start with Darwin the man. One thing that came through to me in doing a story on him a few years ago is that this man who changed the world in many ways was himself quite a cautious fellow. What stands out for you?
DAVID QUAMMEN, Author, “The Reluctant Mr. Darwin”: He was exactly that, Jeff. He was a — he was a man who generated great controversy, but personally he hated controversy. He was a very shy man. He was reclusive. He was a semi-invalid. He was a gentle man, a mild man.
So it was difficult for him, this role that he found himself in. I think of it as the situation of a fundamentally conservative man who found himself burdened with a deeply radical idea.
JEFFREY BROWN: And, Ken Miller, so where did that scientific approach, that rationality, gathering of evidence, where did all that come from?
KEN MILLER, Brown University: Well, I think it came from his upbringing. He lived a rural life. He lived the life of a country gentleman, landed gentry. He had acquaintance with animal breeding and plant breeding. And he had intense curiosity.
He and one of his brothers played endlessly and had experiments — basically, had the ancient equivalent of a chemistry set. And Darwin’s curiosity was something he took with him when he stepped on that boat, the Beagle, for the voyage that you spoke of in the introduction.
And by applying that curiosity, Darwin pondered intensely questions that most people and most of us would have glossed over. Why do different continents have different species? Why do they look as though they descended from a common ancestor? What’s the relationship of fossils to organisms living today?
And it was basically by pondering the answers to all of those questions that Darwin drove himself forward into a most radical set of conclusions, radical for his day, and, for many people today, radical still.
Tension between religion, science
JEFFREY BROWN: Of course, David Quammen, one of the contradictions or tensions that you're both talking about came from his own sense of religion, the religion of the time, and what he was seeing, the theories he was developing.
DAVID QUAMMEN: That's right. He recognized that the theory of evolution by natural selection, once he had formulated it, was a physical explanation for physical phenomena, a deeply materialistic explanation for something that previously had been considered a work of God, special creations by the divinity.
Darwin himself was not a pious person, but his wife was a pious Christian, and he was very considerate of his wife, very concerned for how difficult his dark, materialistic ideas were going to be for her, among others.
JEFFREY BROWN: So, Ken Miller, how do you summarize the key insights that he gave us? And as you look now, 150 years later since the publication of that first main book, what's held up?
KEN MILLER: Well, I think an awful lot has held up. And one of the interesting things about that main book, "On the Origin of Species," is the way he organized it. It's been appropriately summarized as one long argument.
He begins the book by talking about variation in domesticity, by -- where which he talks about the fact that domesticated animals -- pigeons, chickens, cattle -- they differ from each other on an individual basis.
Then he goes to another chapter and says, "You know what? This happens in nature, as well." Then he starts another chapter, and the title of this chapter is "The Struggle for Existence." And Darwin's insight was that all organisms, whether they're plants or animals, are engaged ultimately in a struggle for existence.
So given variation, and the struggle, he then develops an idea. And he allows the reader to come along with him. And that idea is the constant struggle of organisms to survive and reproduce and pass their characteristics along to the next generation, almost automatically generates a process, and that process is called natural selection.
And natural selection, ultimately, for Darwin was the answer to the questions of why species were so exquisitely adapted to their individual environments and also where these species had come from in the first place.
Natural selection idea endures
JEFFREY BROWN: Well, that great phrase, "one long argument," obviously, he was right, because it continued. From within the science community -- I'll start with you, David Quammen, on this -- within the science community, what's still being debated? Or what is reworked and rethought from his original theories?
DAVID QUAMMEN: Well, the basic idea of natural selection as the primary, not the only, but the primary mechanism of evolutionary change has stood the test of time magnificently. And we're getting more and more confirmation all the time from molecular genetics and other dimensions of biology that Darwin was right about evolution in general and about natural selection in particular.
In the meantime, there are refinements that are happening all the time. One of the most famous from the early 1970s is the idea of punctuated equilibria, proposed by Steven Jay Gould and Niles Eldredge.
There are other refinements and elaborations of exactly how evolution by natural selection works. It's a very -- it's a simple idea with a lot of complicated details and complicated implications. Those are still being worked out by brilliant scientists, biologists all over the world, but they are filigree on the great central truth of evolution by natural selection.
JEFFREY BROWN: Ken Miller, you want to weigh in on this aspect of it?
KEN MILLER: Yes, I think I would. David is exactly right in the way he describes natural selection being right as the general mechanism that drives evolution.
But there are still areas of controversy, and I'll give you one of them. There's an enormous and very productive argument and research program going on in the evolutionary biology community as to whether or not the unit of natural selection -- the basic unit upon which natural selection acts -- is at the level of gene, the level of the individual, or, in some cases, at the level of the group.
And there seem to be sorts of evidence that run along all of these lines. So this is an important area.
We still don't really understand the evolutionary forces that led to the evolution of sex. This is also a very contentious area. Almost everybody does sex, from an oak tree to a rabbit, and we want to understand why it's there.
And one of the things, interestingly, that baffled Darwin at the time was the evolution of altruistic behaviors among organisms. The animal kingdom is filled with examples of animals that help each other out, that care for their young, that defend social groups, and he wasn't sure he could explain that.
Well, it turns out that, beginning with William Hamilton and Robert Trivers, a whole new theory built on Darwinian principles called kin selection has emerged in the last several decades that does explain it. But that theory, as well, continues to be explored, and it forms the basis for something we call today behavioral psychology or evolutionary psychology.
Evolution remains controversial
JEFFREY BROWN: And then, of course, Ken, the long argument and the controversy has continued very much in the public sphere. And you, of course, have been a player in some of these, testifying in some of the education debates around the country. Where do things stand now? How do you see it?
KEN MILLER: Well, first of all, within the scientific community, evolution is not just an accepted idea. It's a productive idea. You might say it's a hardworking theory.
Evolutionary analysis is really the basic tool that we use to understand and explore the human genome, among other things. It's the basic tool that we use to control infectious disease, to develop new drugs, and a host of other scientific applications.
But it is fair to say that, within the public sphere, evolution remains a controversial idea. And it's controversial because, quite frankly, a lot of people don't like what they think it is telling them.
Now, there have been struggles around the country, boards of education, state legislatures, and there's even been a few trials. But the outcome of these for the most part, from the point of view of the scientific community, has been positive.
Evolution has emerged triumphant in every court case it's been involved in, with the exception of the Scopes trial. I think ultimately the scientific and educational communities are going to win these debates, win these struggles, and they're going to guarantee kids in our country a good, solid, 21st-century education in science. It's certainly what I'm interested in doing.
Religion at heart of debates
JEFFREY BROWN: Well, let me go back for a last word from David Quammen, because these debates do continue. There's a lot of people who apparently are not convinced. Where do you see things standing?
DAVID QUAMMEN: They do, Jeff and Ken. And I think it's worth making the basic point that the reason there continues to be religious and political controversy over Darwin's ideas is the fact that his theory suggests that Homo sapiens is not a semi-divine species, that it's a species evolved like every other species.
And that's, I think, at the core of the controversy. That is still a genuinely scary, unacceptable idea to a lot of people on religious grounds.
I think it's interesting. I know you're doing some things on Lincoln, who shares his birthday with Darwin. And it's interesting to remember that, 200 years after these two men were born, nobody is fighting about the question of whether Abraham Lincoln's ideas should be taught in the public schools of America, but for Darwin that's still a big issue.
JEFFREY BROWN: All right, the bicentennial of Charles Darwin. David Quammen and Ken Miller, thanks both very much.
KEN MILLER: You're welcome. Happy to be here.
DAVID QUAMMEN: Thank you. Good to be with you, Jeff.