Ghosts in the gene

PUBLISHED : Sunday, 05 September, 2010, 12:00am
UPDATED : Sunday, 05 September, 2010, 12:00am

Pandora's Seed: The Unforeseen Cost of Civilisation
by Spencer Wells
Random House

Humankind has been evolving for about 200,000 years, so why are we still beset with so many problems? That's the question evolutionary biologist Spencer Wells sets out to answer in Pandora's Seed. Quoting a sharp rise in obesity, diabetes, cancer and prescriptions for antidepressants, Wells wonders why our evolutionary mechanisms haven't changed us enough to solve all of our problems. He finds his answer in an event that occurred 10,000 years ago.

It's all about what we would today call a lifestyle change. Before this date, humans were nomadic hunter-gatherers, foraging for food and moving with necessity. But 10,000 years ago we changed into an agriculture-based society that cultivated food and formed permanent settlements. This, Wells says, led to many improvements for our species and laid the foundations for the modern world. But we were biologically ill-fitted for this fundamental change of lifestyle - and diet - and we haven't evolved sufficiently to deal with it. That's why our species still has problems today, Wells proposes.

Wells is a geneticist and follows evolutionary biologist Richard Dawkins' idea that natural selection - the process of evolution - takes place in our genes. Wells sets up Pandora's Seed with a thumbnail sketch of why he believes this, then goes on to lay the anthropological and genetic evidence for his theory of change and evolutionary mismatch.

He then explains the negative effects of our ancient lifestyle shift - disease and dementia, as he calls them. The final part of the book looks towards the future and tries to predict how we will evolve.

Wells is a fine anthropologist and geneticist, and the first 120 pages are full of convincing science. But he proves a lesser futurist and his foray into this area is trite.

Wells gets straight to the heart of the argument in the first chapter, Mystery in the Map. When humans were hunter-gatherers, they simply moved across the landscape looking for food. They reacted to the world, rather than influenced it. But as soon as they settled down, they started to have an impact on their surroundings. Crops were seeded and harvested, and animals were tamed and domesticated. The act of moving to an agriculture-based society was the first step in our species' domination of the planet - and it was so good for us it resulted in an immediate population explosion. That's not scientifically controversial. The interesting thing for Wells is that humans had to adapt to the new order they had wrought - and this forced evolutionary changes in them.

A good example of this, Wells says, is lactose intolerance. Lactase is the enzyme that allows humans to metabolise lactose, the sugar in milk. Babies have a functioning version of the lactase gene which, in some populations, is turned off after childhood. Wells says all hunter-gatherer societies were lactose intolerant - the gene was switched off, because adults didn't use milk as a source of food. But between 10,000 and 8,000 years ago, Middle Eastern populations domesticated the goat and the cow, giving them a ready source of milk. Over time, the lactase gene began to remain active in adults, which allowed them to use milk as a food. In Asia, where milk was never a great source of food, the gene remained switched off.

The change to agriculture brought similar changes on a massive scale, Wells argues. '[The first farmers] were unaware of what, by changing their fundamental relationship with nature, they were unleashing on the world,' he writes. 'Instead of relying on nature's plenty, they were creating it for themselves. By doing so they divorced themselves - and us - from millions of years of evolutionary history, charting a course into the future without a map to guide them through the pitfalls that would occur.'

Population growth, war - which Wells thinks initially occurred when sedentary societies needed to protect their food reserves - and disease were among the negatives that resulted.

Disease is the major problem to result from our 10,000-year-old lifestyle shift. Wells quotes evidence to show that hunter-gatherer societies rarely fell ill. They were more likely to die from trauma, such as being attacked by a wild animal or being hit by a falling tree. Disease is often, although not always, the result of humans living in close proximity to domesticated animals.

'Most of the worst scourges of human health until the advent of vaccination were imports from our farm animals, including measles, tuberculosis, smallpox and influenza,' he writes.

To make it worse, populations had grown and people lived in close proximity to each other, so diseases could spread. Agricultural societies were exposed to diseases that our poor hunter-gatherer bodies had not evolved to cope with.

Wells does cover many of the evolutionary benefits of the lifestyle change, although he's less clear about how they arose. Humankind's capacity for abstract thought, as manifest in the arts, only came about when people stopped moving around. Non-nomadic societies had more time on their hands because their lives were less labour-intensive, Wells says. This somehow led to art and our ability to conceptualise. Wells is muddled about this, although there has been quite a bit of research into this still confusing area.

A recent New Scientist magazine article proposed ideas for the evolutionary benefits of art. Geoffrey Miller thinks art arose as a form of peacock-like sexual display: it showed an intelligence and imagination that would have made the artist seem like a strong partner to a prospective mate. Brian Boyd thinks the artistic impulse developed as a way to explore new horizons in a safe environment, something that aids the useful trait of innovation. Wells' arguments seem woolly in comparison.

Although the book's title implies some shock that we haven't evolved perfectly to deal with our environment, this will come as no surprise to evolutionary biologists. Wells doesn't mention it, but evolution in terms of a single species - let alone that of a whole society - is never perfect. Evolution is a process that adapts what's already there - a bit like adding on a bit of code to a computer program to make it perform a new function. It's a law of making do, not of elegance. 'Natural selection only requires something to work, not to work as well as it could,' Michael Le Page writes. 'Botched jobs are common.' Le Page quotes the panda's 'thumb' which it uses to grasp bamboo. It is, in fact, a wrist bone. The real thumb is useless because it's fused to the paw.

Perhaps societies aren't evolving on an upward path to utopia at all. Dawkins proposed that evolution was a gene-based selection process that was always moving a species closer to perfection. Wells, who applies Dawkins' gene-based view to his work, seemingly agrees with the idea that evolution should be progressive, that evolution should always make a society better. Yet the evidence he presents shows that although the shift to agriculture was a great advance for humanity, it also brought a new set of worrying problems with it.

It would be interesting to know what the late Stephen Jay Gould, also an evolutionary biologist, would have said about Wells' theory. Gould argued vociferously against Dawkins' dominant view. For him, evolutionary change was more about diversification than progress - things didn't necessarily move towards perfection, they just changed into something different. So society may not be evolving towards utopia. It might just be changing to overcome difficulties as it finds them - and creating a new set of problems as it goes.

It's a view that could explain a lot about the world that we live in and how we got here.