MOTHER NATURE’S LAWS
STUART PIMM
Doris Duke Professor of Conservation Ecology, Nicholas School of the Environment, Duke University; author, A Scientist Audits the Earth
Writing from Sarawak, Alfred Russel Wallace nailed the most important law of living things in a crisp eighteen words: “Every species has come into existence coincident both in space and time with a pre-existing closely allied species.”
With judicious editing, Wallace could have fit his 1855 “laws of evolution” paper into today’s word limits of PNAS or Nature. We don’t find trilobites scattered in the Devonian, Jurassic, and Eocene with nothing in between. The paper screams for an explanation of the bundled generalities of paleontology and biogeography, but the scientific community was asleep at the wheel and barely noticed. A few years later, that absence of notice forced Wallace to send his deep, elegant, and beautiful explanation to Darwin for moral support. Darwin had the same explanation, of course.
What other laws has Mother Nature given us for biological diversity?
The average geographical range of a group of species is very much larger than the median range.
The average of the geographical ranges of 1,684 species of mammals in the New World is 1.8 million km2, but half of those species have ranges smaller than 250,000 km2—a seven-to-one ratio. For the region’s three main bird groups, the ratio is five and eight times, and for amphibians, forty times. There are many species with small ranges and few with large ranges.
There are more species in the tropics than in temperate regions.
The first explorers to reach the tropics uncovered this law. Rembrandt was painting birds of paradise and marine cone shells in the early 1600s. Wallace went first to the Amazon because collecting novel species was how he earned a living.
Species with small ranges concentrate in places that typically are not where the largest numbers of species live.
This just doesn’t make sense. Surely, with more species, one should have more species with large ranges, small ranges, and everything in between. It isn’t so. Small-ranged species concentrate in some very special places. About half of all species live in a couple of dozen places that together constitute about 10 percent of the ice-free parts of the planet.
Species with small ranges are rare within those ranges, while those with large ranges are common.
Pardon the language, but Mother Nature is a bitch. You’d think she’d give species with small ranges a break—and make them locally common. Not so. Widespread species tend to be common everywhere, while local ones are rare even where you find them.
What inspired Darwin and Wallace were encounters with places rich in birds and mammals found nowhere else—the Galapagos and the islands of Southeast Asia. There are no such places in Europe. Darwin spent most of HMS Beagle’s voyage too far south in South America, while Wallace’s first trip was to the Amazon. The Amazon is very rich in species, but it is a striking example of the law that such places rarely have many species with small ranges. (I suspect this cost Wallace dearly, because his sponsors wanted novelty. He found novelty on his next trip, to the East.)
Scientists found widespread species first. Darwin and Wallace were among the first naturalists to encounter the majority of species—those with small geographical ranges concentrated in a few places. Even for well-known groups of species, those with the smallest ranges have been discovered only in the last decades.
What deep, elegant, and beautiful explanation underpins these ineluctably connected laws? There isn’t one.
Given the observed distribution of range sizes, the tropics have to have more species simply because they are in the middle of the globe. Sufficiently large ranges must span the middle—that’s the only way to fit them in. But they need not be at the ends—temperate or arctic places. Yet middles have more species than ends even when the middles aren’t tropical. There are more species in the middle of Madagascar’s wet forests, though the northern end (with fewer species) is closer to the equator, for example.
Moreover, warm, wet middles—tropical moist forests—have more species than hotter and drier middles. The correlation of species with warmth and wetness is compelling, but a compelling mechanism is sometimes an illusion.
Small-ranged species can be anywhere—near middles or near ends. They are not. They tend to be on islands (the Galapagos, the Malaysian archipelago), and on “habitat islands”—mountaintops, like the Andes. This fits our ideas on how species form. Alas, they are not on temperate islands and mountains, so Darwin and Wallace had to leave home to be inspired. Except for salamanders: The Appalachians of the Eastern United States seem to have different species under every rock, forming a theoretically obstinate temperate center of endemism unmatched by birds, mammals, plants, or, indeed, other amphibians.
To make matters worse, all this assumes that we know why some species have large ranges and more have small. We do not. In short, we have correlations, special cases, and some special pleading, but elegance is missing. A deep explanation need not be there, of course.
Our ignorance hurts. Concentrations of local, rare species are where human actions drive species to extinction 100 to 1,000 times faster than the natural rate. Yes, we can map birds and mammals and so know where we need to act to save them. But not butterflies, which people love, let alone nematodes. Without explanations, we cannot tell whether the places where we protect birds will also protect butterflies. Unless we understand Mother Nature’s laws and extend them to the great majority of species still unknown to science, we may never know what we destroyed.
THE OKLO PYRAMID
KARL SABBAGH
Writer and television producer; author, Remembering Our Childhood: How Memory Betrays Us
New explanations in science are needed when an observation isn’t explicable by current theory. The power of the scientific method lies in the extraordinary richness of understanding that can emerge from an attempt to devise a new explanation. It’s like an inverted pyramid, with the first observation—often just a slight departure from the norm—as the point and then ever widening layers of inference, each dependent on a lower layer, until the whole pyramid supplies a satisfying and conclusive explanatory whole.
One of my favorite such explanations dates from 1972, with the observation of a small anomaly in a routine sample of uranium ore from Oklo, a region in the Haut-Ogooué Province of the Central African state of Gabon, which was analyzed in a French laboratory. Rock samples of naturally occurring uranium usually contain two types of uranium atoms, the isotopes U-238 and U-235. Most of the atoms are U-238, but about 0.7 percent are U-235. In fact, to be accurate, the figure is 0.72 percent, but the sample that arrived in France had “only” 0.717 percent, meaning that .003 percent of the expected U-235 atoms were missing.
Such differences in proportion were known to occur only in the artificial surroundings of a nuclear reactor, where U-235 is bombarded with neutrons in a chain reaction that transforms the atoms and leads to the change in the naturally occurring proportions. But this sample had come from a mine in Gabon, and at the time there was no nuclear reactor on the whole continent of Africa, so that couldn’t be the explanation. Or could it?
Nearly twenty years earlier, scientists had suggested that somewhere on Earth the conditions might once have existed for a uranium deposit to act like a natural nuclear-fission reactor. They proposed three necessary conditions:
The size of the deposit should be greater than the average length that fission-inducing neutrons travel, which is about 70 centimeters.
U-235 atoms must be present in a greater abundance than in natural rocks today, as much as 3 percent instead of 0.72 percent.
There must be what is called in a nuclear reactor a moderator, a substance that “blankets” the emitted neutrons and slows them down so they’re more apt to induce fission.
These three conditions were exactly those that applied to the Oklo deposits 2 billion years ago. The deposits were much larger than the m
inimum predicted size. Moreover, uranium-235 has a half-life of 704 million years, decaying about six times faster than the U-238 atoms, so several half-lives ago (around about 2 billion years) there would have been much more U-235 in the deposits—enough to lead to a sustainable chain reaction. Extrapolating backward, the relative proportions of the two isotopes would have been approximately 97 to 3, rather than 99.3 to 0.7 as it is today. And finally, the layers of rock had originally been in contact with groundwater, suggesting that what happened was the following:
A chain reaction would start in rocks surrounded by water, and the uranium atoms would split and generate heat. The heat would turn the water to steam, destroying its ability to moderate the reaction, and the neutrons would escape, stopping the reaction. The steam would condense back into water and blanket the neutron emission. More neutrons would be retained, splitting the atoms and restarting the chain reaction.
Explaining a tiny anomaly in the ratio of two types of atom in a small piece of rock has led to a description of a series of events that happened in a specific location on Earth billions of years ago. Over a period of 150 million years, a natural nuclear reactor would produce heat for about half an hour and then shut down for two and a half hours before starting up again, producing an average power of 100 kilowatts, like that produced in a typical car engine. Not only is this explanation deep, elegant, and beautiful, it’s also incontrovertible. It doesn’t depend on opinion or bias or desires, unlike many other “explanations” of how the world works, and that’s the power of the best science.
KITTY GENOVESE AND GROUP APATHY
ADAM ALTER
Psychologist; assistant professor of marketing, Stern School of Business, New York University
The most elegant explanation in social psychology convinced me to pursue a PhD in the field. Every few years, a prominent tragedy attracts plenty of media attention because no one does anything to help. Just before sunrise on an April morning in 2010, a man lay dying on a sidewalk in Queens. The man, a homeless Guatemalan named Hugo Alfredo Tale-Yax, had intervened to help a woman whose male companion had begun shouting and shaking her violently. When Tale-Yax intervened, the man stabbed him several times in the torso. For ninety minutes, Tale-Yax lay in a growing pool of his own blood as dozens of passersby ignored him or stared briefly before continuing on their way. By the time emergency medical workers arrived to help, the sun had risen, and Tale-Yax was dead.
Almost half a century earlier, another New Yorker, Kitty Genovese, was attacked and ultimately killed while dozens of onlookers apparently failed to intervene. A New York Times writer decried the callousness of New Yorkers, and experts claimed that life in the city had rendered its citizens soulless. As they would in response to Tale-Yax’s death, pundits wondered how dozens of people with functioning moral compasses could possibly have failed to help someone who was dying.
Social psychologists are taught to overcome the natural tendency to blame people for apparently bad behavior and to look instead for explanations in the environment. After Genovese’s death, social psychologists Bibb Latané and John M. Darley were convinced that something about the situation explained the bystanders’ failure to intervene. Their elegant insight was that human responses aren’t additive in the same way that objects are additive. Whereas four lightbulbs illuminate a room more effectively than three lightbulbs, and three loudspeakers fill a room with noise more effectively than two loudspeakers, two people are often less effective than a single person. People second-guess situations, they stop to make sense of a chain of events before acting, and sometimes pride and the fear of looking foolish prevent them from acting at all.
In one of a series of brilliant studies, Latané and Darley videotaped students as they sat in a room that slowly filled with smoke.* The experimenters pumped smoke into the room with a smoke machine hidden behind a wall vent, the effect suggesting that there might be a fire nearby. When a subject was alone in the room, he usually left quickly and told the experimenter that something was amiss. But when a subject was surrounded by two or three others (some of them confederates, who were instructed to sit there immobile) he often remained seated, even as he lost sight of the others through the pall of smoke. When interviewed later, these students said they chose not to act because they concluded the smoke was benign (steam, or air-conditioning vapor), and they claimed that they had paid little or no attention to how the others in the room reacted.
According to Latané and Darley, the patterns of thinking that distinguish us from lower-order animals ultimately undermine our willingness to help in such situations, when we are alongside other people who are equally diffident.
THE WIZARD OF I
GERALD SMALLBERG
Practicing neurologist; playwright, Off-Off Broadway productions, Charter Members, The Gold Ring
Consciousness is the fusion of immediate stimuli with memory that combines the simultaneous feeling of being both the observer and the observed into a smooth, enveloping flow of time that is neither truly the past nor the present but somehow inexplicably each of them. It is the ultimate authority and arbiter of our perceptual reality. That consciousness is still an intractable problem for scientists and philosophers to understand is not surprising. Whatever the final answer turns out to be, I suspect it will be an illusion the mind evolved to hide the messy workings of its parallel modular computing.
Neurophysiologists are finding, as they pull ever so slightly at the veil that shrouds the “Wizard of I,” that this indispensable attentive and observant self-monitor called consciousness is dependent on a trick in overseeing our perceptions. Our subjective sense of time does not correspond to reality. Cortical-evoked potentials—electrical recordings—of the normal brain during routine activity have been shown to precede by almost a third of a second the awareness of an actual willed movement or a response to sensory stimulation. The cortical-evoked potentials indicate that the brain is initiating or reacting to what is happening far sooner than the instantaneous perception we experience. On a physiological scale, this represents a huge discrepancy that our mind corrects by falsifying the actual time an action or event occurs, thus enabling our conscious experience to conform to what we perceive.
But data even more damaging to our confidence in the reliability of our perceptions come from studies of rapid eye movements, called saccades, that are triggered by novel visual stimuli. During the brief moments of these jerky eye movements, visual input to the brain is actively suppressed; we are literally blind. Without this involuntary ocular censorship, we would be repeatedly plagued with moments of acute blurred vision that would be unpleasant as well as unsafe. From a survival calculus, this would pose an extreme disadvantage, since it would invariably occur with novel stimuli, which by their very nature require not the worst but the best visual acuity.
The Wizard’s solution to this intolerable situation is to exclude those intervals from our stream of awareness and replace them instead with a vision extrapolated from what just occurred to what is immediately anticipated. Consciousness, like a former president, has to come up with an accounting for the erased period. Evolution provided a much longer epic to work out the bugs in this necessary deception than the limited time frame under the gun of a special prosecutor. Instead of trying to hide the existence of the tape, consciousness came up with a far cleverer trick of obscuring the deletion. It does this by falsifying the time, backdating those necessary moments so that there is no appearance of any gap.
This illusion of visual continuity from inference and extrapolation reveals an innate vulnerability in the brain’s software that any good hacker can exploit. Magicians, card sharks, three-card-monte hustlers have made a nice living working this perceptual flaw. In a comic routine, Richard Pryor expressed this best when caught by his wife with another woman. “Who are you going to believe? Me or your lying eyes?”
ONE COINCIDENCE; TWO DÉJÀ VUS
DOUGLAS COUPLAND
Writer, artist, designer; author, Marshall McLuha
n: You Know Nothing of My Work!
I take comfort in the fact that there are two human moments that seem to be doled out equally and democratically within the human condition, and that there is no satisfying ultimate explanation for either. One is coincidence, the other is déjà vu. It doesn’t matter if you’re Queen Elizabeth, one of the thirty-three miners rescued in Chile, a South Korean housewife, or a migrant herder in Zimbabwe: In the span of 365 days, you will pretty much have two déjà vus and one coincidence that makes you stop and say, “Wow, that was a coincidence!”
The thing about coincidence is that when you imagine the umpteen trillions of coincidences that can happen at any given moment, the fact is that in practice, coincidences almost never occur. They’re so rare that when they do happen they’re memorable. This suggests to me that the universe is designed to ward off coincidence whenever possible. The universe hates coincidence; I don’t know why—it just seems to be true. So when a coincidence happens, that coincidence had to work awfully hard to escape the system. There’s a message there. What is it? Look. Look harder. Mathematicians perhaps have a theorem for this, and if they do, it might, by default, be a theorem for something larger than what they think it is.
What’s both eerie and interesting to me about déjà vus is that they occur almost metronomically throughout our lives—about once every six months, a poetic timekeeping device that, at the very least, reminds us we are alive. I can safely assume that my thirteen-year-old niece, Stephen Hawking, and someone working in a Beijing luggage factory each experience two déjà vus a year. Not one. Not three. Two.
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