Can Bioengineers Make Human Beings More Sustainable?
Nature already tried that, and look how it turned out.
Scott Olson/Getty Images.
Matthew Liao, Rebecca Roache, and Anders Sandberg are philosophers with a modest proposal on climate change: Let's bioengineer future children for sustainability. We need to reduce carbon emissions, so let’s make people smaller, eat less meat. We need to share sacrifices and work together, so let’s alter our progeny to be more cooperative. It's not exactly Gattaca; it's more like Jonathan Swift meets Craig Venter. As Sandburg later hinted to the Guardian, the new white paper might be seen as academic trolling—lobbing a verbal bomb and waiting for the explosion.
Bioengineer people to protect the climate? As an anthropologist, I had a less dramatic reaction. Been there, done that.
You see, there already was a world where people bioengineered their children to stave off global climate catastrophe. You probably don't know it, but you're one of their offspring.
The last warming trend—the one that created the race of mutants we are today—happened 10,000 years ago, as a result of the Earth’s natural orbit cycles. Our planet rounds the Sun not in a perfect circle but a slightly squashed one. Plus, it spins all wobbly like a top. The combined squashing and wobbling make for a 100,000-year-long carnival ride that plunges the Earth into long Ice Ages interrupted by short windows of warmth.
For most of our existence, humans have reacted to the climate roller coaster by enjoying the good weather while it's around and otherwise hiding in the warm tropics. When the climate warmed by several degrees around 8,000 B.C., it must have seemed at first like a wonderful dream. The glaciers melted. The human population grew and grew. There were more people than ever before, using a broader range of resources and eating a broader range of foods, and they invented beautiful and complex cultures.
That's when these people of the early Holocene did something truly bizarre. They reacted to all this climate change by engineering a new, more sustainable ecology. And they began to foster mutant children who would flourish in an alternate, globally warmed future.
It's in all the history books. Well, the prehistory books, anyway. You've no doubt heard about the birth of agriculture, the dawn of cities, the growth of early civilization. In the years since the Human Genome Project, though, we’ve begun to uncover the massive genetic changes that accompanied these historical events. And many of these natural shifts in the genome correspond to the very modifications that Liao, Sandberg, and Roache would have us insert into our DNA via artificial means.
Consider the philosophers' first suggestion about how we might bioengineer humanity to cut back on greenhouse emissions. Since meat production belches carbon dioxide and methane, they suggest that the future human race should have a built-in genetic aversion to meat.
Well, that's nothing compared to what Holocene people accomplished. In Ice Age Europe, 50,000 or so Neandertals subsisted on a diet that was at least 80 percent meat. Most of that came from large mammals like bison, elk, horse, and mammoth. Modern humans later ate the same foods, helping to drive the mammoth, woolly rhinoceros, aurochs, and many other prey animals to extinction.
But hunting big animals to extinction was not the only option. People in Mesopotamia, China, Mexico, and other places invented a new ecology, depending on more sustainable rabbits, birds, and shellfish. They collected grains so intensively that the grasses began to rely on us to disperse and plant them.
These were the first farmers, staying in one place to plant and harvest. Some groups began to domesticate animals and then to milk them. Switching from hunting to a sedentary farming lifestyle generated more calories with fewer carbon emissions, because milk is much more efficient than meat. They weren't worried about atmospheric greenhouse gases, of course, but their new lifestyle allowed for a more efficient use of Earth's natural resources.
What do these lifestyle changes have to do with genetic engineering? They wouldn't have been possible without modifications to human biology. Prehistoric children naturally lost the ability to digest lactose, or milk sugar, as they got older. So in order to create a culture of dairying, which allows for a reduction in meat intake, our ancestors had to undergo some kind of genetic mutation—one that allowed them to consume lactose throughout their lives. We've now identified five versions of this shift in the human genome. That means there were five milky X-Men born less than 10,000 years ago, and who today have hundreds of millions of descendants around the world.
Most people today descend from early farmers, and are thus likely to carry a bigger genetic change. Saliva drips with an enzyme called amylase, which allows you to start converting starchy foods into sugar before they even hit your stomach. Lots of modern humans carry duplications of amylase in their genome, taking some of us from the original two copies of the gene to as many as 14. More copies make more amylase, breaking down starches faster. Having so many copies of the amylase gene is another bioengineered trait that has flourished over the last 10,000 years, allowing for a faster and more efficient caloric return from grains.
When it comes to cutting meat, natural selection has acted more like an entrepreneur than a eugenicist. Instead of giving us an aversion to meat, it lures us away from meat by offering a milkshake sweetened with corn syrup.
What about Liao, Sandberg, andRoache's other suggestions? Should we make children smaller, so they'll use less metabolic energy?
Early Holocene people did shrink. By developing a smaller mass, smaller stature, and smaller brains than their ancestors, our ancient relatives lived this specific form of bioengineering. Shrinking brains may have been favored by selection, but much of the change in height and weight came from malnutrition relative to hunter-gatherers. Their fabulous diet, which seems like it should have been more efficient and healthier, actually led to a raft of problems: bad teeth, stunted growth, and new viruses and parasites. At least initially the new, low-impact lifestyle brought with it a lower standard of living.
But humans' real bioengineering coup came later: We became bioengineers ourselves. Centuries and then millennia of tinkering led to the development of hybrid corn, fatted cattle, and tomatoes that survive shipping. The Green Revolution made us bigger, but whatever the impacts of pesticdes and nitrogren fertilizers, it also allowed us to raise more calories in less space.
So if we’ve undergone all these extreme changes, why are we still suffering from a damaged environment? It's true that we've learned and evolved ways to cut our dependence on meat, increase our reliance on sustainable and renewable foodstuffs, and pack ourselves into densely-populated urban areas. Humans today can draw hundreds of times more calories from each acre of land than they did as ancient hunter-gatherers. But these changes haven’t reduced our impact on the Earth; they've merely enabled us to grow the population a thousand times over. The bioengineering that came about 10,000 years ago led to more people, not less consumption.
Here's another problem: Natural selection is often a good engineer, but it’s slow. Ten thousand years later, milk-drinking still isn't universal. We resist many old diseases, but can't outrun some new ones. The cruelty of evolution is a lottery that exacts a high death rate for every useful mutation. Nature’s bioengineering doesn’t bother with human ethics. But then, maybe our future bioengineers won’t, either.
Population growth was the subject of Jonathan Swift’s original, trolling call for legalized cannibalism. It seems like bioengineering won’t be of much use unless we dare to adopt a truly Swiftian approach. Don’t breed meat-hating children; breed children with a taste for human flesh.
John Hawks is an anthropologist at the University of Wisconsin-Madison who specializes in human evolution and genetics. He maintains an anthropology weblog.