National Geographic : 2017 Apr
48 national geograpHic • april 2017 allowing her to feel connected to the motions of the Earth and interpret them through dance. “I guess I got jealous,” she says. “We will transcend all of the limitations of our biology,” Kurzweil promised. “That is what it means to be human—to extend who we are.” Clearly Harbisson’s antenna is merely a beginning. But are we on the way to redefining how we evolve? Does evolution now mean not just the slow grind of natural selection spreading desirable genes, but also every- thing that we can do to amplify our powers and the powers of the things we make—a union of genes, culture, and technology? And if so, where is it taking us? conventional evolution is alive and well in our species. Not long ago we knew the makeup of only a handful of the roughly 20,000 protein-encoding genes in our cells; today we know the function of about 12,000. But genes are only a tiny percentage of the DNA in our genome. More discoveries are certain to come—and quickly. From this trove of ge- netic information, researchers have already identified dozens of examples of relatively recent evolution. Anatomically modern humans migrated from Africa sometime between 80,000 and 50,000 years ago. Our original genetic inheritance was appropriate for the warm climates where we first evolved from early hominins to humans, from knuckle-walkers to hunters and gatherers. But a lot has happened since that time, as humans have ex- panded around the world and the demands posed by new challenges have altered our genetic makeup. Recent, real-life examples of this process abound. Australian Aboriginals living in desert climates have a genetic variant, developed in the past 10,000 years, that allows them to adjust more easily to extreme high temperatures. Prehistorically, most humans, like other mammals, could digest milk only in infancy—we had genes that turned off the production of the milk-digesting enzyme when we were weaned. But around 9,000 years ago, some humans began to herd animals rather than just hunt them. These herders developed genetic alterations that allowed them to continue making the relevant en- zyme for their whole lives, a handy adaptation when their livestock were producing a vitamin-rich protein. In a recent article in the Scientist, John Hawks, a paleoanthropologist at the University of Wisconsin–Madison, wrote how impressed he was at the speed with which the gene was disseminated: “up to 10 percent per generation. Its advantage was enormous, perhaps the strongest known for any recent human trait.” Similarly, the ancestors of all non-Africans came out of Africa with dark skin. Indeed even 10,000 years ago, according to researchers, European and African skin looked much the same. But over time humans in darker north- ern climates evolved less heavily pigmented skin, which helped absorb the sun’s ultraviolet rays and synthesize vitamin D more efficiently. The Inuit of Greenland have an adaptation that helps them digest the omega-3 fatty ac- ids in fish far better than the rest of us. An indigenous population near the Argentine town of San Antonio de los Cobres has evolved to be able to drink Making tools One of our first cultural adaptations expanded our diets. With better nourish- ment, we could develop bigger, more complex brains. Bipedalism Our early ancestors may have adapted to walking on two legs as an efficient way to travel long distances, possibly to find new kinds of food. Lack of fur Early humans may have developed skin without thick fur in order to keep cool on the savanna and make body parasites easier to find.