National Geographic : 2017 Apr
Beyond Human 49 the high levels of arsenic that have occurred naturally in their groundwater. Evolution is relentless; when the chance of survival can be increased, it finds a way to make a change—sometimes several different ways. Some Middle Eastern populations have a genetic variation that’s different from the one northern Europeans have to protect them from lactose intoler- ance. And there are a half dozen distinct genetic adaptations that protect Africans against malaria (one has the significant drawback of also causing sickle-cell anemia, if the altered form of the gene is inherited from both parents). In the past 50 years researchers have uncovered a variety of ad- aptations in Andeans, Ethiopians, and Tibetans that allow them to breathe more efficiently at high altitudes. Andean populations retain higher levels of oxygen in their blood. Among Tibetans there is evidence that a gene was introduced through interbreeding with Denisovans, a mysterious branch of the human lineage that died out tens of thousands of years ago. All these adaptations give indigenous people living at high altitudes an advantage over the woozy visitor gasping for oxygen in the mountain air. early in origin of species, Charles Darwin comes out fighting: “Natural Selection, as we shall hereafter see, is a power incessantly ready for action, and is immeasurably superior to man’s feeble efforts, as the works of Nature are to those of Art.” The book was published in 1859. Is what was true then still true today? Was it true even in Darwin’s lifetime? Biological evolution may be implacable, and indeed more skillful than the genetic evolution humans can effect with crossbreeding in plants and animals, but how important is it, measured against the adaptations we can devise with our brains? To paraphrase the paleoanthropologist Milford Wolpoff, if you can ride a horse, does it matter if you can run fast? In our world now, the primary mover for reproductive success—and thus evolutionary change—is culture, and its weaponized cousin, technology. That’s because evolution is no match for the speed and variety of modern life. Despite what evolution has accomplished in the recent past, think of how poorly adapted we are to our computer screens and 24-hour schedules, our salty bags of corn chips and pathogen-depleted environments. Why are our internal clocks so rigid? Why can’t our seemingly useless appendix, which may have once helped us digest grass, shift to break down sugars instead? If human genetics were a tech company, it would have gone bank- rupt when steam power came along. Its business plan calls for a trait to appear by chance and then spread by sexual reproduction. This works nimbly in mice, which can produce a new litter in three weeks, but humans go about things more slowly, producing a new gener- ation only every 25 to 35 years or so. At this rate, it can take thousands of years for an advantageous trait to be spread throughout a population. Given genetic evolution’s cumbersome protocols, it’s no surprise technology has superseded it. Technology now does much of the same work and does it far faster, bolstering our physical skills, deepening our intellectual range, and allowing us to expand into new and more challenging environments. “People get hung up on Darwin and DNA,” says George Church, Blushing The embarrassment and uncomfortable tingling of a blush can signal remorse and elicit forgiveness from peers in a social group. Tears of emotion Crying shows vulner- ability and increases the chances of receiving help, which, in turn, strengthens social bonds in a group. Bigger brains As we gathered into larger social groups, bigger brains developed along with more complex com- munication and problem-solving.