Spencer Wells, a geneticist and anthropologist, had studied the genetics of indigenous human populations for years when, after working on the PBS documentary about the Y chromosome, “The Journey of Man,” he found a home at National Geographic. “They said, ‘This is fascinating stuff. Now that you’re done with the film, what would you like to do next?’ It’s a great question to be asked,” said Wells, who is now the “Explorer-in-Residence” for the magazine. His work took him around the world and ultimately toward writing Pandora’s Seed: The Unforeseen Cost of Civilization, which, as he discusses below, argues that the switch to agriculture 10,000 years ago is the root of many a modern problem, from obesity to religious fundamentalism to social anxiety.

Q. What did you learn from the time you spent in hunter-gatherer societies?

A. As a relatively affluent, middle-class American going to visit these people who have virtually nothing, the first thing that strikes you is, how can they live like this? They must be so unhappy. But as you spend more time with them, you unwind from the Google and mobile-filled world and you realize they’re incredibly happy and have a wonderful lifestyle, though it’s increasingly under threat. Left to their own devices, they would be completely fulfilled. So you have to ask, why is everyone in the world today an agriculturalist? Ninety-nine point nine percent of us rely on agriculture rather than hunting and gathering. That led me to do some research, to ask, what led to that transition, and what effects did that transition have on us, physically and mentally? The early agricultural populations were less healthy than hunter-gatherers, so why did their way of life lose out?

It’s because with agriculture, you can grow more people, even if they’re not happier or healthier. That set in motion a lot of forces that I trace in the rest of the book.

Q. When did the transition from hunter-gathering to agriculture happen, and what effect did it have on humans?

A. Around 10,000 years ago. The world was coming out of from the last Ice Age, conditions were improving, the world was warming up and the human population started to expand somewhat in certain locations. People started to specialize in gathering particular grain species – wheat and barley in the Middle East, rice in China and India, corn in Mexico. They started to settle down into villages. Then an ice dam melted in North America. The water of Lake Aggasiz, which had been created by the melting of the Laurentide ice sheet, was released into the North Atlantic.  This killed the Gulf Stream, which brings warm water into the North Atlantic. It plunged western Eurasia back into Ice Age-like conditions, but population density had by that point increased beyond the ice age carrying capacity. So people had to innovate, and the innovation was agriculture.

We survived. It made complete sense at the time to develop agriculture. The sting in the tail was that as population density increased, we overhunted the animals we survived on. So we had to domesticate some species. Most major infectious diseases that afflict humans were introduced then, from these domesticated animals. There was also a shift in the human diet away from a diverse gathered group of plants. Hunter-gatherers in the Middle East were eating over 150 plant species – fruits, nuts, berries, tubers as well as grains. Once they made the transition to agriculture, it went down to about eight plant species, with most calories coming from wheat and barley. Even today, 60 percent of the world’s calories come from wheat, rice and corn. Consumption of starch and simple sugars increased, and there was a massive increase in cavities right away, no matter where the population was – the Middle East, Asia, the Americas. As soon as people transitioned to agriculture, cavities quintupled. It’s an early sign that we were maladapted to the new way of life. That continues today – the obesity epidemic is an extension of that.

Q. Why did we evolve this way if it seems to have been bad for us?

A. Evolution is all about reproduction. In a Darwinian sense, agriculture was real winner. It produced more people. But of course, it’s not just about making more people, it’s a question of choosing the lifestyle that’s right for us. We’re still in the course of adapting to this radical cultural shift. For instance lactase, the gene that codes for the enzyme that digests lactose, the sugar in milk.  Certain populations that  domesticated sheep, goats, and cattle, and started drinking milk beyond childhood were selected to retain that ability.  As a result, most Europeans today have it. You can see evidence of this sort of culturally-driven selection in the human genome.

Q. What other modern problems came about because of our transition to agriculture – what were the mental impacts in particular?

A. There is some mental fallout. The predicted ideal human group size is around 150 people, according to the British evolutionary psychologist Robin Dunbar. That’s what the neocortex, which governs the ability to form social relationships, can handle. He predicted we should be living in groups no larger than 150. It remains an important figure – it’s the size of army companies, the size of traditional Hutterite farming communities in Canada (they are a bit like the Amish). Once you go beyond 150, the group fissions. If a group size exceeds 150 people, you need to create some sort of bureaucracy, a government, because otherwise you can’t keep track of all the social relationships.

Today, we’re living in cities with thousands and millions of people. But we’re actually disconnected from most of them. Imagine you’re in an elevator – you’re not chatting with anybody, you’re checking your Blackberry, perhaps, or staring at the floor numbers. You’re crowded, but disconnected. I argue that this creates unease.

We actually do see rising rates of mental illness. The World Health Organization predicted that by 2020, mental illness will be the second leading cause of death and disability after heart disease. Antidepressants are the most widely-prescribed class of drugs today. As I say in the book, for the first time in human history, we have to drug ourselves to feel normal. We used to do it, with shamans, for instance, to get out of the normal state of existence, to enter a mystical trance.  Now we do it to make it through the day.

Q. You discuss in Pandora’s Seed how fundamentalism can be traced back to these problems as well – can you elaborate?

A. Most think only of Islamic fundamentalism, but there is also Christian fundamentalism, particularly in the U.S. I argue that both are the product of the last 50 years or so, and are in part due to a sense that some people have that they’ve lost their purpose, a religious purpose, the overarching sense of what is ethical, in all-out race to create novelty and material wealth. Religious fundamentalism is perhaps a backlash against that, along with the increasingly secular world we live in. It’s an effort to go back to an earlier time, where mythos – received truths and traditions – was more important than logos, than rational thought.

Q. How can we repair some of these problems?

A. It’s not going to be easy – we have a lot of crises facing us in the 21st century.  We should, I argue, take some cues from surviving hunter-gatherers, and our distant ancestors, and try to want less. Look at the Gulf of Mexico oil spill, for instance. There are proximal causes to that – errors made by BP, perhaps coupled with a lack of regulation and oversight. But ultimately, the root cause is that we all need cheap gasoline. We as a society are ultimately to blame. Everyone is ringing their hands about climate change and so on, but really, part of the solution is simply to learn to want less – to live more efficiently, recognizing that there are limits to our previously unchecked growth.

Q. Is that enough, given that the problem seems part of our genes?

A. That is something that needs to underlie everything else we do. We also need to come up with better, cleaner sources of energy, pursue material wealth less, and develop better farming methods. I think all of that comes down to wanting less. What’s going to happen over the next half century, for the first time in 70,000 years, is we will be living in a population that’s no longer growing. The UN is predicting around 9.5 billion people by mid-century. That’s a lot of people, especially people who want to live the way the average American lives today. It’s simply untenable to imagine that. I think for all of us to survive, we have to get by on less and be more efficient with the resources we use.

Q. Are you optimistic about our ability to change in this way?

A. There is hope – that’s why I called it Pandora’s Seed. The myth of Pandora is that she opens the box, and all these plagues for humanity fly out. But she claps down the lid and saves hope. Hope lies in our remarkable ability to innovate. It’s what saved us time and time again throughout history. I think it’s going to allow us to create solutions, once we see the consequences of what we’re doing. We are fairly short-sighted as a species. But we’re at a point in our social evolution where we need to think longer-term in order to see the true costs, the unintended consequences of our actions.

*Photo of Spencer Wells by David Evans. Photo of wheat courtesy bernat….