Improbable Destinies: Fate, Chance, and the Future of Evolution

As a child in the evangelical South during the 1970s, I was taught that “Darwin” was a bad word. My textbook for the creation of life was the opening chapters of Genesis, Yahweh’s six days of exquisite labor and then an extra day to chill. One week. The notion of evolution and its timeline — billions of years — seemed a heresy cooked up by egghead scientists and Satanic secularists. Just four decades and forty miles away from the infamous Scopes trial, I sang “I’m No Kin to the Monkey” along with my peers in Sunday School: I don’t know much about his ancestors / But mine didn’t swing from a tree. Anti-Darwinism remains as American as God, guns, and apple pie: a recent poll revealed that nearly half of adults believe in a divine creation of a universe only a few millennia old.

But since the mapping of the human genome in 2000, we’ve confirmed beyond a shadow of a doubt that humans are primates, sharing over 99 percent of our coding DNA with chimpanzees, whose own sequence tracks more closely to ours than to gorillas or orangutans. The genomics revolution has proven that Darwin was a prophet, his legacy still debated by evolutionary biologists across the globe. In his new book, Improbable Destinies: Fate, Chance, and the Future of Evolution, Harvard biologist and zoologist Jonathan B. Losos infuses a sense of whimsy and playfulness into the staggeringly complex problems of evolution, explaining why the evidence must be tested and re-tested, new data introduced, with each generation of scientists.

A lizard specialist, Losos has pursued his fieldwork in mostly tropical archipelagos, where he’s studied anoles and how their scattered populations morph into similar body shapes, with virtually identical nutrition and behavior, depending on the ecological niches they inhabit.

Tahiti, Bermuda, Madeira, Bali. Everyone loves islands but no one has nesiophilia — the inordinate fondness and hungering for islands — more than an evolutionary biologist. Darwin drew much of his inspiration from island stopovers on the fabled voyage of the Beagle . . . Each oceanic island or archipelago is a world unto itself, the evolutionary goings-on there independent of what happened elsewhere. That means that by comparing one island to another, we can get a sense of evolutionary potential and predictability.

The occasional hurricane would wipe out Losos’s slithery subjects, but he gleaned enough data to build an argument: presented with wildly different environments, species usually fill open niches in predictable ways — the concept of convergent evolution. In other words, if you could roll evolution’s dice over and over, you’d get the same (or similar) results each time.

Improbable Destinies takes us on a whirlwind odyssey, from vibrant Caribbean jungles to English grasslands to innovative swimming-pool labs in Seattle, surveying a spectrum of species: guppies, moths, deer mice, bacteria. He recounts myriad experiments that show that Darwin was wrong about one pillar of his theory: evolution doesn’t always move at a glacial pace but rather can be observed within a few generations (or over the course of a biologist’s career): “The resistance of rats to developing cavities, the tendency of fruit flies to fly toward light, and fruit fly tolerance of alcohol fumes . . . pick any trait that varies in a population, impose artificial selection, and you will get an evolutionary response.”

The literary scholar Harold Bloom once asserted that “the meaning of a poem is always another poem,” but his maxim could apply to science writing as well. Behind Improbable Destinies lurk David Quammen’s The Song of the Dodo and Jonathan Wiener’s Pulitzer Prize–winning The Beak of the Finch, but Losos’s major influence is Stephen Jay Gould’s 1989 masterpiece, Wonderful Life, whose detailed analysis of the Burgess Shale’s wealth of Cambrian fossils posits that life on earth could only have evolved the way it has once — rewind the tape and you’ll get different chemistry, different avenues of natural selection, different flora and fauna, and so on. (Gould’s title is an homage to Frank Capra’s 1946 film, which allows James Stewart a glimpse of a notional world in which he’d never been born.) Losos both explicitly and implicitly engages Gould’s ideas; and in a twist that Darwin would have loved, he reaches no firm conclusion. “Start with identical circumstances and you’ll usually — but definitely not always — get a pretty similar outcome.”

Improbable Destinies is a crackling good read, threading rich anecdote into trenchant science. It belongs on the same shelf as I Contain Multitudes, Ed Yong’s gorgeously crafted account of microbes and their critical roles in our bodies; Nick Lane’s dense, groundbreaking work on the origins of life, The Vital Question; and other recent books that grapple with Darwin’s revolution, such as Richard O. Prum’s The Evolution of Beauty and Robert M. Sapolsky’s Behave. Ours is an era of paradigm shifts in science, with a bonanza of literature that captures our world’s breathtaking diversity as well as its dire future. As Losos notes, “The elephant in the room, of course, is global warming . . . one seven-year-long experimental study on worms detected replicated genetic changes associated with warmer soils. I predict that this is just the tip of the melting iceberg and that soon we will detect many physiological, behavioral, and anatomical changes convergently evolved in vulnerable species.”

Given that climate change may be our most daunting challenge — and given that all kinds of species, from worms to fish to germs, will mutate rapidly to accommodate these shifts — books such as Improbable Destinies offer a roadmap for our species, from the African savannahs to inundated coasts. Fortunately for readers, Losos and Yong and Sapolsky are also every inch the prose stylists as the majority of fiction writers promoted with more fanfare. It’s high time to transform the hearts and minds of Americans hostile not only to evolution but the crisis that is already forcing the world’s next cycle of rapid biological change. It’s high time we act — our evolutionary future may pivot on what we do next.

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