Population geneticist Spencer Wells explores humanity's ancient roots
Population geneticist Spencer Wells explores humanity's ancient roots
Amateur genealogists may trace their line-age back a few centuries, finding an ancestor who stopped at Ellis Island or hitched a ride on the Mayflower. But when Spencer Wells talks about the human family tree, it's on the order of millennia. Wells, a population geneticist with the National Geographic Society, is currently serving a three-year term as a Frank H.T. Rhodes Class of '56 Professor. His latest book, Pandora's Seed, explores what he calls "the unforeseen cost" of human civilization.
Cornell Alumni Magazine: Your official job at National Geographic is "Explorer in Residence."
Spencer Wells: It's a great title, though somewhat oxymoronic.
CAM: Does it say "explorer" on your business cards?
SW: Believe it or not, it does.
CAM: How cool is that? SW: Yeah, I love it.
CAM: The classic image of an explorer is a Victorian in a pith helmet penetrating the wilds of Africa. In our wired, Google-mapped world, is it still possible to be an explorer?
SW: There is still exploration to be done, but not in the same way as when it was meant to claim territory for the crown. It's not just about going to exotic places. Now it's motivated by scientific discovery.
CAM: Part of your job is directing the society's Genographic Project. What is that?
SW: We humans are close to identical at the genetic level— 99.9 percent or so. But of course there is variation, and in population genetics we study the patterns of that variation to infer past demographic events. The Genographic Project is studying basic questions about human history. Where do we come from as a species? Am I related to that person down the block or to someone halfway around the world? We use genetic markers to study how people have migrated around the planet over the last 60,000 years or so.
CAM: In addition to studying the genomes of tribal peoples, the project has sold more than 365,000 mail-in test kits. Why have so many people spent $100 to have their DNA analyzed?
SW: It's partly the idea that you're carrying this history book inside you that you can't read on your own. We're helping them decipher this historical document.
CAM: What did you learn from having your own DNA tested?
SW: My dad's family came from England many generations ago, so I'm carrying the genetic lineage common in English men. But before they were in England, they over-wintered the worst part of the last ice age in Spain. Before that they were in central Asia, so roughly 40,000 years ago they were hunting wooly mammoths on the steppes of what is now Kazakhstan and Ukraine. And before that they were part of the first wave of migration out of Africa into the Middle East, roughly 45,000 years ago. Ultimately they trace back to Africa within the last 50,000 years, just like everybody else.
CAM: One of the most striking parts of Pandora's Seed is the chart showing that by some measures—like height and bone density—humans were extremely healthy 10,000 years ago, then saw steep declines that have reversed only in the last century. How is that possible?
SW: Early on, it probably had to do with the shift away from a diverse diet. The average hunter-gatherer in the Middle East prior to the development of wheat and barley agriculture was subsisting on about 150 plants, plus the animals they killed. Once you make the shift it drops to about eight; you go from a diverse diet with lots of nutrients to relatively simple carbs. Male Paleolithic hunter-gatherers were five-foot-nine, five-ten, and that dropped to about five-three within a couple of thousand years, and it took a long time to get back to those heights.
CAM: Why did agriculture win out? SW: Because you can grow more people. That's ultimately what it's all about—a numbers game.
CAM: In the book, you visit places from Vienna to Polynesia to . . . Dollywood. What did a Tennessee theme park teach you about human history?
SW: I didn't set out to trek to Dollywood; we were driving somewhere and my kids wanted to ride rollercoasters. But what I noticed was the incredible prevalence of obesity. I talk about how the food that's meant to nourish us is killing us through Type 2 diabetes, heart disease, and cancer. So what about our way of life led to that?
CAM: That connects to this "unforeseen cost of civilization" that you talk about in your book. Can you elaborate?
SW: First we have to ask, why are we agriculturists? It's an unusual thing to do; as far as we know we are the only species that consciously made this decision to shift from being hunter-gatherers.
CAM: So why are we a species of farmers?
SW: When the last ice age ended roughly 15,000 years ago, people around the world started to focus on gathering grains like wheat, barley, rice, and the ancestor of corn. These were fantastic sources of carbohydrates and calories, and populations expanded and settled into villages. But the melting ice caused a massive lake to form in North America. Eventually that cold water flowed into the North Atlantic and killed the Gulf Stream, and the Northern Hemisphere was plunged back into an ice age for about 1,000 years. Yet people had built villages; they couldn't just become nomadic hunter-gatherers again. So a few began planting their food, and when this tough period ended population expanded massively. People over-hunted animals, so they were forced to domesticate cattle, sheep, and goats, and that introduced new diseases. So there were unintended consequences, even early on, from this decision to plant seeds.
CAM: What lessons can humans learn from this ancient past?
SW: Our society continues to have this image of ourselves expanding infinitely, that resources are unlimited, and now we're coming to see the costs of that thinking. The lesson is that we need to stop expanding so much—to learn to want less, to be more like our ancestors who lived more in "harmony" with nature. There's no reason for a hunter-gatherer to kill 50,000 antelope or 500 or even five. They kill what they need on a daily basis; any more is just waste. But for us, excess is part of how we live.
— Beth Saulnier