On Thursday, astronomers announced that they’d reached a new milestone in the search for Earth’s “twin,” or a planet much like ours that orbits in what’s known as the Goldilocks Zone—not too close to its star, nor too far away. In the five years since NASA launched the Kepler satellite to look for such worlds, the best we’ve been able to find is a portly cousin that is forty per cent larger than Earth. But the new discovery, called Kepler-186f, is only ten per cent bigger than Earth. Though it’s not exactly a twin, it’s a much closer relative. And so, despite its distance (five hundred light years from Earth), it automatically becomes a candidate in any future search for life. Earth, after all, is the only example we have of a life-producing world, so for decades we have sought its mirror image—a rocky world that’s neither too hot nor too cold to have liquid water on its surface. The search for intelligent alien life has proceeded along similar lines—it began with radio telescopes trained skyward to detect the sort of signals that we make.
Yet, even as the Kepler mission gets closer to finding a mirror image of our own planet, many scientists have ceased believing that we should be looking for ourselves in space. There are other ways for a planet to support life, they argue—and there are other ways for life to be intelligent.
That’s the point of a recent paper in Acta Astronautica by the dolphin-behavior researcher Denise Herzing. She warns against the seductive tendency to turn the question of a creature’s intelligence into one about how similar that creature is to humans. Instead, she writes, we need “a non-human biased definition and measure of intelligence.” This would allow us to identify signs of intelligent life that a human-centric explorer might overlook—for instance, in creatures without limbs to manipulate their surroundings, mouths to make sounds, or even brains to process information. (After all, microbes and plants learn about and react to their environments.)
Herzing’s paper proposes five indicators of intelligence that any given species or machine (she includes artificial intelligence in her assessment) might combine in its own way: first, the size of the subject’s brain (if it has one) relative to the rest of the body; second, the extent to which an entity sends and receives information; third, the degree to which individual members of a species are distinct from one another; fourth, the complexity of the being’s social life; and, fifth, the amount of interaction it has with members of other species. One way to be intelligent is to score high on all five measures, as dolphins do, for instance. Dolphins’ brains are more than four times larger than they “should” be for their body size (only humans have a higher “encephalization quotient,” as this ratio is called). Dolphins send and receive a great deal of information through their sounds and gestures. Each dolphin is a unique individual, with a personality and style that makes it easy to distinguish it from others. Dolphins have elaborate social lives. Finally, dolphins interact in varied ways with other species—with Herzing and her colleagues, for example, and also with other dolphin species, fish, and sharks—instead of ignoring them.
However, there are many other ways to combine the five intellegence criteria, even on Earth. Herzing asked experts on a variety of earth-dwellers (bacteria, octopuses, computers) to rate their subjects on each of the five metrics. Putting all the answers on the same spreadsheet revealed different profiles of intelligence, depending on how the five traits (or their absence) were combined. Intelligence might have big brains and be communicative but non-social. Creatures might communicate with one another and interact with their surroundings, but have no brains. We have already experienced (if not appreciated) some of these combinations here on Earth, Herzing notes. She lines up some examples like characters in a comic book: that brainy, communicative, nonsocial Loner is a profile that fits many a species of octopus; the Crowd of units that communicates and acts but has no brain or individuality is a good description of many types of bacteria. Social insects like bees and ants fit the profile Herzing calls the Busy Body (“detail oriented and follows authority, smart but low potential for creative interaction”). Artificial intelligence has a profile (brainy and detail-oriented, not social or engaged with other species) that Herzing calls the Accountant. And, finally, there is the Party Animal, communicative and socially interactive. That describes humans. It also fits the dolphin.
Of course, the quest to imagine true alien intelligence can only go so far. In “A Walk in the Dark,” Arthur C. Clarke described beings completely unlike us—“like the gas-beings of Alcoran or the roving wave-lattices of Shandaloon.” These creatures might not even notice us as they pass around or through us. A broader definition of intelligence won’t just encourage us to look for creatures that we might otherwise have missed, Herzing says. It will also help us figure out which forms of intelligence we can’t reach. One reason she used “interaction with other species” as one of her criteria is because a creature that scores zero on that measure is not going to be too interested in us.
“I was thinking in terms of, Well, why do we want to know this, anyway?” Herzing told me. We might find a splendidly complex creature out there that has no interest in being sociable with its would-be friends from Earth. Grasping this could help us avoid unpleasant misunderstandings—like that moment at the end of Stanislaw Lem’s novel “Fiasco” where an astronaut, having hacked away at some unsightly mounds on the ground, comes to realize that the mounds are the intelligent aliens he was looking for.
Of course, it’s kind of discouraging to think the human race could spend so much hope and effort on the search for life only to find roving wave-lattices and other beings that won’t, or can’t, talk with us. But you can also see the expansion of our quest for intelligence as exhilarating. It raises the possibility that life out there will be interestingly, perhaps shockingly, different. The alternative possibility is that the problems of life and intelligence are the same everywhere, which means that evolution will keep converging on the same answer on Earth and on any other planet—and what could be less encouraging of space travel than the thought that the journey’s end would reveal more of the same? Better to wrestle at the edges of comprehension than to expect, as Wallace Stevens once wrote of Heaven, “that they should wear our colors there, and pluck the strings of our insipid lutes.”
Quelle: The New Yorker