Humans Now Evolving Faster

A new study finds that humans are now changing more rapidly than at any point in history. John Hawks, assistant professor of anthropology at the University of Wisconsin Madison and a lead author of the report, explains why.

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LUKE BURBANK, host:

Well, despite what it might look like when you turn on "Mind of Mencia" or "Dancing with the Stars," humans, it turns out, are actually evolving faster than ever and becoming more genetically diverse in the process.

This according to a new study led by John Hawks of the University of Wisconsin Madison who joins us now to tell us more about it. Hi, John.

Dr. JOHN HAWKS (Assistant Professor, Anthropology, University of Wisconsin-Madison): Hi.

BURBANK: Thank you very much for coming on.

Dr. HAWKS: Sure.

BURBANK: This study has been getting a lot of attention the last couple of days. For people who just kind of breezed passed the headline, what is sort of the take-away paragraph from this study that you did?

Dr. HAWKS: Well, we looked at evidence for a recent natural selection in the human genome; that's Darwin's process of evolutionary change. We were looking specifically for genes that had changed rapidly in the last 40,000 years. And when we counted them all up, there were thousand of them - thousands of them in human populations in Europe, in West Africa, and in East Asia. And that rate of change, the sheer number that we saw, is probably about a hundred times faster than we've ever seen evolution going before.

BURBANK: So, our genes are changing and evolving and getting better at a faster rate. Are they getting better?

Dr. HAWKS: Well, I tell my students this: Darwin doesn't care how smart you are, how - you know, how pretty you are. All that natural selection cares about is how many kids do you have, so what we're getting better at is surviving through the hardships that affect us as kids - diseases, hunger - and we're getting better at having more and more kids.

ALISON STEWART, host:

And can I throw out my little bit of Darwin, my mom was a high school biology teacher.

Dr. HAWKS: Yeah.

STEWART: Now, the whole idea of Darwin is that it isn't that you're the bigger or stronger or faster, it's that you adapt the best to your environment.

Dr. HAWKS: That's exactly right, yeah.

STEWART: So there are no short-necked giraffes because they all died off because they couldn't reach the leaves.

Dr. HAWKS: Yeah.

STEWART: That's the one thing I always think in my head.

Dr. HAWKS: So, when we're talking about the kinds of changes that are happening - let me give you an example. In Europeans, there's a form of a gene called lactase which digests the sugar in milk that continuous to be active when you're adults. So northern Europeans can drink milk - no problem - most people in the world can't do this. They drink lots of milk when they're adults - they get sick from it; that's a very recent change that's happened within the last 10,000 years.

BURBANK: What do you attribute this to? I mean, beyond just the fact that we're - people are, you know, having more survival ability with their kids and stuff. Is this more kids means more chances for the genes to adapt?

Dr. HAWKS: Yeah, there's basically two things that are explaining why things change fast. One is that we've changed the way live: We started planting crops. we developed agriculture, we started living in cities that caused more disease, and it caused new social pressure on us. The other thing is that there's a lot more people and that gives us more possibilities for the very rare mutations that do good things for us.

BURBANK: This sort of is jumping ahead to a question I was going to ask a little later, but we've been kind of broaching it, and that is about natural selection. I mean, there was a time when living a while and having kids that even survived, and that you were probably the most adaptable, the smartest, kind of the cream of the crop; now, anybody can do it. Is that bad for natural selection?

Dr. HAWKS: Well, in the sense that if you wanted humans to look a particular way in the future, you know, you can't predict what humans will look like.

BURBANK: How about not playing Nintendo all the time, how do we select for that?

Dr. HAWKS: Well, I'll tell - I was on "Flush Out"(ph) yesterday and I said, you know what, natural selection - it's there, and if you're playing Nintendo all the time, today, it doesn't make that much difference, you know, because people aren't dying at different times, but they are having different numbers of kids, so it still continues. But there's some things that you might not expect, like we're having kids later in life that, for a lot of people, causes infertility problems. And that's a sorting where some people are able to do it, and other people can't. And in the future, what you would see is a genetic change toward being more able to reproduce late.

BURBANK: Mm. Well, you told our producer when he was interviewing you before the show that this isn't really something that's supposed to necessarily predict the future, it's more looking at what has happened. But what are the repercussions of this? Scientifically, what do we take away from this?

Dr. HAWKS: Well, I think that there's a couple of things that are really interesting in terms of how human history happened, what made things happen in the past. One thing is that when we're looking at selection, we're looking at the ability of populations to grow ultimately. And so, population growth has driven migrations; it's driven warfare; it's driven where people have been able to settle and how they interacted. So we're going to be able to explain some of those aspects of human history.

The other thing is that a lot of these new selected genes have medical importance. Some of them are involved in Alzheimer's disease; some of them are involved in autism; some of them were involved in metabolic diseases like Type II diabetes. So we'll be able to understand more about why people today have health problems.

BURBANK: You know, whenever you start talking about certain groups of people and how they're physically different or genetically different, it becomes kind of fraught with this tension that maybe you're saying, oh, these people are genetically smarter or better. I mean, is there scientific evidence to support that, and are we too squeamish about talking about this because it starts to sound racist or something?

Dr. HAWKS: Well, you have to think about the broad scope of what human diversity means. There has, in the past, been selection in different places for different things. For instance, sub-Saharan Africans have been under very strong selection associated with malaria. They have new genes that help them to resist it. Some of those genes are really effective in resisting some forms of malaria; some are less so. But that's a force of selection that was never very strong in Europe. So that's one source of differences - they're adapted to different things.

Another source of differences is this change has been happening so rapidly that different populations have ended up with different genes that actually do the same thing, so East Asians and Europeans are both light-skinned populations. Those skin-color genes are mostly very recent, but they're different genes in Europe from the ones in East Asia. They're evolving in the same - directionally I would say - they're both getting lighter skinned, but it's a different genetic mechanism that does it in each place.

BURBANK: So you don't get grief from people who say that this is, you know, the bell curve revisited - "Bell Jar" - bell curve.

STEWART: "Bell Jar," Sylvia Plath.

BURBANK: Okay, I knew I was getting that mixed up. This isn't the bell - this isn't sort of, you know, leading us up to the bell curve?

Dr. HAWKS: Well, you know there are a large number of genes in our lists that are neurological in some sense - they do something to the brain. It's possible that we're going to find that there are behavioral variations that have been under selection in the past. Right now, we can't say that because we don't have a good clue about what a lot of these brain mutations do functionally, but the idea that humans should be identical everywhere is just unlikely from an evolutionary standpoint. So what's important is understanding exactly how in history people were selected in different ways to understand exactly what was going on to try to diversify them.

BURBANK: John Hawks, assistant professor of anthropology at the University of Wisconsin Madison, lead author of a recent study about the phase of evolution which - congratulations, world. We're doing it faster than ever.

Thanks, John.

Dr. HAWKS: Thank you.

STEWART: I would have taken his class.

BURBANK: I know.

STEWART: I know. That was your professor?

BURBANK: He's gotten a lot smarter in the last seven minutes.

STEWART: Oh.

BURBANK: Except I'm still (unintelligible) though.

(Soundbite of laughter)

STEWART: You're getting smarter even in the next seven minutes. We're going to make you care about the Fed rate or at least an economist from Barron's Weekly is going to do his darndest(ph). That's what's coming up on THE BRYANT PARK PROJECT from NPR News.

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