Spencer Wells is not a stereotypical scientist. A big man with rugged features and chin stubble that looks as if it's been sun-dried for a week in a desert wind, he looks the anti- thesis of the etiolated laboratory worker in a white coat.
In fact, although his day job is in human genetics, Wells is also the National Geographic's explorer-in-residence – which must be one of the most enviable, if baffling, job titles. Being an explorer for an organisation renowned for its adventurous streak is probably most people's idea of a dream job, but can it really be done "in residence"?
Wells laughs out loud when asked what it's all about. "It's a great title isn't it, but somewhat oxymoronic," he says. All that it means, he insists, is that he has a long-term relationship with National Geographic centred around its Genographic Project – which attempts to document the long migratory history of our early ancestors by analysing the genetic make-up of people living today.
Wells, once the director of the Population Genetics Research Group at Oxford University and now a visiting professor at Cornell University, is the scientific front man of the Genographic Project. For the past five years, the project has collected thousands of DNA samples from indigenous tribes around the world in an attempt to study the flow of genes and people from one part of the globe to another. "I said we needed to sample the world's DNA properly, to sample the world's genetic diversity, and that became the Genographic Project. So we are using DNA as a tool to track ancient human migrations," he says. Anyone with an interest in their evolutionary history can participate in the project, providing they are willing to pay the $100 (£68) for the home sampling kit, which comprises two small tubes to collect the cheek cells rubbed off in the inside of the mouth with the help of a couple of sterile rubbing sticks.
The Genographic Project emerged from an idea Wells developed following the disintegration of an earlier study called the Human Diversity Project, which fell apart acrimoniously following criticisms of it being a neo-colonial attempt to exploit the genetic resources of indigenous peoples.
The earlier project was the brainchild of Wells' post-doctoral supervisor, the population biologist Luigi Luca Cavalli-Sforza, who believed it was imperative to collect and store DNA samples from the many indigenous tribes in the world before they disappear though the combined forces of disease, enforced migrations and intermarriage. But some indigenous groups took great exception to what they saw as an attempt to raid their genetic resources. Even today, some tribes, such as the North American Navajo Nation, have a blanket ban on such genetic sampling, believing it does nothing to help their plight. "They are afraid of the consequences, afraid of being exploited. We've made contact with them and offered to make an ethical protocol, but nothing has really happened, unfortunately," Wells says.
Meanwhile, the Genographic Project is having more success with other indigenous groups, reassuring participants that the goal is to understand their own ancestral origins. "It's certainly learning from past mistakes, particularly how you work with indigenous and traditional peoples. That's what ultimately killed the Human Diversity Project," says Wells. All the DNA samples collected for the Genographic Project are held anonymously and the genetic analysis looks only at portions of the genome that tell of gross relationships between groups of people, rather than anything more specific to do with family relationships or medical problems.
"It's like entering into a contract. You agree to look at certain genetic markers and not look at others. The indigenous people are aware of all this, and they understand the work that's being done," Wells explains. The project has collected some 55,000 DNA samples from indigenous people, and is on track to hit 70,000 by the end of next year, when the first phase of the £25m project finishes. This is nevertheless some 30,000 samples short of the original target of 100,000 samples.
In addition, however, the project has sold some 360,000 kits to members of the public, who send off their tissue samples in the post and follow their subsequent laboratory analysis on-line through a unique, anonymised code. This can give a person a rough idea of the geographical origins of their maternal or paternal ancestry.
There is, however, a limit to what the genetic "markers" we carry in our DNA can tell us about our ancestry origins. By its very nature, the analysis can only tell us of one strand of our ancestry, and not the many dozens of other strands that have made us what we are. Wells accepts this: "Absolutely. This isn't the sum total of your ancestry." But it is the DNA from the indigenous tribes that can potentially provide insight into the global movements of our early ancestors. "Indigenous people have some sense of identity that is apart from the mainstream in society. They are somewhat isolated in some cases, often speaking a unique language, but there is some sense of connection to their ancestors and the place where they live that most of us don't have," he says.
Like the many other kinds of study into this area, the results clearly point to an African origin of anatomically modern humans, something that both the palaeontology and the genetics agree on. "Probably the most astounding thing for me, as someone who has studied anthropology, genetics and biology for decades, is just how recent it was when we left Africa," Wells says. "It shows that every member of our species was living in Africa as recently as 60,000 years ago. It's only in the past 60,000 years – which is a couple of thousand human generations – that we've left that continent to populate the rest of the world also, and in the process generated 6,000 different languages and all the different physical appearances that we see today. So all of that has happened very quickly, in an evolutionary sense," he says.
The results of the Genographic Project so far suggest that large-brained Homo sapiens went through a dramatic population crash about 70,000 years ago, when global numbers plummeted. This led to a population bottleneck, or a squeeze in genetic diversity, that can still be seen in the DNA of modern populations; we as a species are less genetically diverse than other primates. "It's worth getting the message out, that we are related to one another, that we are much more closely related genetically than people may suspect from glancing around and looking at these surface features that distinguish us; so that's an important social message," Wells says. "Race, in terms of deep-seated biological differences, doesn't exist scientifically. We are 99.9 per cent identical roughly, at the genetic level. That's actually a remarkably low level of genetic diversity compared to other species of large primates. It represents a population bottleneck event some 70,000 years ago when the population dropped down to as few as 2,000 people. We came back from that, and our genome reflects that."
Soon after this population bottleneck – or perhaps because of it – some humans migrated out of Africa across to Asia and Europe, and then later to Australia and the Americas. It was at about this time that humans were undergoing another change. They invented better stone tools, used body ornaments and practised art. "Figuring out what made us behaviourally modern 70,000 years or so ago is probably a Nobel-prize-winning question in anthropology," Wells says. Then, about 10,000 years ago we invented agriculture and underwent the most dramatic of all changes to our lifestyle. From semi-nomadic hunter-gatherers, we settled down to a life of farming that led to a dramatic expansion of the population and the establishment of cities and organised religion and culture.
The ramifications of this transition, the subject of Wells' latest book, Pandora's Seed: The Unforeseen Cost of Civilisation, are still with us today. "Many of the crises we see in the 21st century, I would argue, have their roots in the dawn of the Neolithic," he says. "We spent an enormous amount of time as hominids and as primates living as hunter-gatherers. That is the natural way for us to live, and we're suddenly living in this profoundly unnatural way, and we're still in the process of adapting to it and working out how to live with it."
The shift from a hunter-gathering lifestyle to an agricultural way of life, he believes, has not just led to many of the environmental problems we face today, it has caused some of dire medical disorders, from infectious diseases and obesity to the mental illnesses that are rampant in modern, urban living. "Since we settled down, population density increased massively. We became sedentary and the foods we ate changed enormously from the days we were hunter-gatherers," he explains. "We were once used to living in groups of no more than about 150 individuals. Now we live in cities of millions and the cultural cacophony creates a feeling of unease and we are seeing evidence of that with the rise of mental illness."
Despite the immense problems facing the human species in the 21st century, Wells believes there is hope – what he calls "Pandora's seed". When Pandora opened the box, she at least had to slap it shut fast enough to contain hope. "The hope is that humans are innately innovative and that we can innovate very rapidly when we're forced to," Wells says. Our one hope for continued survival, he seems to suggest, is the innate creativity of the same large brain that arguably helped to create much of the mess we find ourselves in today.
'Pandora's Seed: The Unforeseen Cost of Civilization' is published by Allen Lane (£20). To order a copy for the special price of £18 (free P&P) call Independent Books Direct on 08430 600 030, or visit www.independentbooksdirect.co.uk