by Barry Lopez
As it happens, the morning after we’re told that someone’s father has been bitten by a puff adder is actually the morning Kamoya has chosen for us to go to Lodwar to replenish our supplies. First we drive both Land Rovers to a Turkana settlement where the older man is reported to be near death. As we approach the man’s awi napolon (the thornbush-encircled residence of a prominent male), we see the man who supposedly needs to get to the hospital right away sitting outside, waiting for us in his finest clothes, holding his mkwaju.
“Nobody at death’s door here,” Kamoya says as we pull up.
The man simply wants to see Lodwar, where he’s never been.
Both vehicles quickly fill with women, men, and children. Several more cling to the spare tire mounted on the rear door and clamber onto the roof, straddling the tanks of extra fuel secured up there in the roof rack with another spare tire.
It takes a long while to reach Lodwar. When we arrive, Kamoya explains to everyone the time and place to regroup for the return trip. Everyone scatters. Not all of them return to the rendezvous at the appointed hour, though others replace them. On the return trip to Nakirai we drop some people off and pick others up, including the man who was not bitten by a puff adder. Disgusted with Lodwar, he had started walking home soon after he got there. Some of the people who hitched a ride with us had never been inside a motor vehicle. They marvel at how the side windows slide open, at how the door handles work.
People standing on far-off rises in the land with their goats stare at us as we pass. People inside the vehicle, sitting in the middle seats, shout with all their strength to hail them. The herds of goats break like waves over elevations in the scabbed land.
* * *
—
OCCASIONALLY WHEN I can’t sleep I take my binoculars out and gaze into the wilderness of constellations above, the silver path of the “milk road” we pass beneath as the night advances. It seems to me that I can sometimes feel the planet rotating underneath me and I imagine sunlight falling hard on the other side of my darkness, falling on French Polynesia. When I was a boy, there were no other planets to be aware of outside the immediate companions of the sun. Now we know there are hundreds of planets out there, just in our own galaxy. Radio telescopes, which can see where we can’t, have made images of them. When I was learning about Copernicus’s universe, people thought all life depended on photons—incoming solar radiation—to survive. Today we know that tube worms and other life-forms living around thermal vents on the oceans’ floors don’t need sunlight in order to make their sugars. They require only sulfur. When I was in grade school, people thought most all life on Earth roamed the surface of the planet or swam in its waters. Today we know that the greater part of Earth’s biomass lives underground. When I was learning to swim, people believed that the continents were stationary. Now children are taught that 120 million years ago South America and Africa sailed apart, and that 50 million years ago India plowed into Asia, creating the Himalayas.
In order to gather in the stars directly above me, I have to focus my binoculars out beyond a rete mirabile of thin, crisscrossing acacia limbs overhead, with their tiny, moisture-hoarding leaves. I locate the supernova 1987A in the Large Magellanic Cloud to orient myself, and then search for some of the less complicated southern constellations I’m getting to know—Triangulum Australe, a small constellation close to the south celestial pole, and Crux, the Southern Cross, the long axis of which points almost exactly to that spot, the south celestial pole. (In the Northern Hemisphere, a triple star system, Polaris, twinkles in the night sky one degree from the north celestial pole; in the southern sky, there is no comparable star to serve as a stationary marker.)
I can easily locate the Small Magellanic Cloud, 210,000 light-years away. Both “clouds” are apparent to the naked eye. They seem to be part of the Milky Way, but each is actually a galaxy entire unto itself. Taken together, the Magellanic Clouds represent a portal that opens onto the nearer realms of deep space. Astronomers include both, along with the Milky Way, in our Local Group, fifty-four or so galaxies, many of them dwarf galaxies, forming together a thin ellipsoid, distinctly separated from the galaxies of other local groups. In this ellipsoid, Andromeda stands at one end and the Milky Way at the other, about 2.5 million light-years apart. Our Local Group is one of about fifty such local groups arrayed relatively close to us. Astronomers organize all these local groups into superclusters. Each local group in a supercluster might contain anywhere from a dozen to a thousand galaxies. The number of superclusters in the known universe runs into the millions.
The calculations outstrip meaning.
To pull far back to something easier to imagine—our own galaxy, with only about one hundred billion stars in it—and focus again on the Southern (latinate) Cross, I can distinguish four terminal stars, one at each end of its two arms. The closest of the four to us is Gamma Crucis (Gacrux), only about 90 light-years away, while the farthest off, Beta Crucis (Mimosa), is about 353 light-years away. The Southern Cross (Crux), one of the smaller of the southern constellations, also frames most of a dark nebula called the Coalsack. And the Coalsack is visually adjacent to a loose swarm of about a hundred brilliant young stars collectively called the Jewel Box. Like every other constellation, Crux is a three-dimensional object with a two-dimensional identity.
If I were to dig down this evening into the rocky soil under my head and find the cranial cap of a Pliocene hominin, could I determine how this individual took in the stars? With only this remnant stony basin, part of a distant relative’s head, could I learn what these stars provoked in her? Or him. I have to think it provoked nothing. It’s too early in our history, they say, for such thoughts of the stars.
Some nights, when a slight breeze puts the limbs of the acacias into a gentle motion, the barely audible sound of this soughing mimics for me the hum of the stars, and the glitterings of these suns seem like the overtones that sometimes carry beyond the bowing of stringed instruments. On those nights I might try to force the ramulose arrangement of these convoluted branches and twigs into the as-yet-unsettled pattern of human evolution. The trunk of the tree represents the kingdom Animalia. Where major limbs branch off into various phyla, I follow the one that represents chordates, the animals with backbones, and from these the branch representing the class Mammalia, the mammals. From that branch another diverges, the one that represents the primates, starting some 55 to 65 million years ago. Here, among the Eocene prosimians and Oligocene anthropoids, among hominids like Sivapithecus, Proconsul, and the Old World monkeys, I might find a road leading to the primates who read books. We’re all right picking this trail up about 30 million years ago with Aegyptopithecus, a possible ancestor living in the early Oligocene. In the mid-Miocene, fifteen million years ago, Kenyapithecus is a possible ancestor. The path from there to Homo is indistinct. Baffling, really.
A few not-for-sure hominids—Sahelanthropus tchadensis, Orrorin tugenensis, Ardipithecus kadabba—turn up in late Miocene deposits. Gracile (i.e., slender, lithe) australopithecines are present by the early Pliocene and one of them, possibly Australopithecus afarensis, might be a direct ancestor. By now the ancestors of gorillas and chimpanzees are well along on their own paths. Gorillas diverge from the human line about 11 million years ago, chimpanzees about 7.7 million years ago. At this juncture, one might hope to imagine a continuous line, as one species of hominin evolves into another, and then that one evolves into yet another, but this kind of thinking is fundamentally flawed. The actual evolution of Homo sapiens and every other animal along the branches of this imaginary tree is dazzlingly complicated.
The conceptual problem is easy to visualize. Most of us are familiar with the popular branching diagrams found in textbooks that represent evolution with neat lines of continuous descent, where the lines divide and subdivide like this:
The difficulty with this diagram is that evolution doesn’t proceed in this manner. It works more l
ike this:
Lots of dead ends and genetic variations, together with some interbreeding. Some lines of descent run closely parallel for long periods of time before terminating or branching off in a noticeable way. An additional complication is that evolution in the animal kingdom actually looks a bit more like this:
as, for example, when Homo sapiens and Homo neanderthalensis, whose lines diverge about 450,000 years ago, interbreed in Europe or western Asia 400,000 years later, producing a “hybrid” human cohort that soon dies out but which leaves virtually all non-African humans with a small percentage of Neanderthal genes.
Succinctly put, it’s hard to say precisely where any individual human being came from. We all seem to have descended from relatively small, isolated human populations, many of which might have interbred at some point and some of which conserved the genes that give them a distinct look. Walk down the streets of Montreal or Singapore or Istanbul and you can see how varied the species H. sapiens is, even though from a certain perspective we all look pretty much alike. Paleoanthropologists like to point out that individual humans in the taxon Homo sapiens are more closely related to chimpanzees in the taxon Pan troglodytes than sheep are to goats. (Humans and chimpanzees share more than 98 percent of their genes.)
* * *
—
STARING INTO THE distant treetops, looping and swirling in the night breeze, and hoping for more of the order of life than nature offers, I wish the wind would drop. I’d like the branches to stand utterly still so I might discern in all that jumble a single continuous line to H. sapiens. But, figuratively speaking, the breeze never lets up. Even if it did, it would be easy to miss any single branch obscured by another, or to perceive two branchlets emerging from the same branch when in fact each is growing from a separate branch. Or to make sense of any instance of inosculation, of one branch growing into another, which has occurred in the history of H. sapiens.3
The path of human evolution is not the completely hopeless muddle it might seem to be, however. The problem is that the tree is a misleading metaphor, one, and two, there are too few human fossils extant for anyone to be definitive about what preceded us in the hominin line. These conceptual and empirical problems, although very real, can be set aside temporarily, however, in order to say that we do have a fairly good idea about who our recent ancestors were.
Most paleoanthropologists generally agree that roughly 11 million years ago, in the mid-Miocene, a single primate gave rise to two separate lines of development. One—both are still ongoing—is represented today by the gorilla (Gorilla gorilla). The other line, sometime in the late Miocene, came to be represented by a primate whose own genetic line eventually diverged into two separate lines of expression. One line, that of primates ancestral to chimpanzees, led to the chimpanzee and bonobo (Pan paniscus) of our time. The other line produced the hominins, some of which are ancestral to humans. These ancestors all eventually disappeared as distinct species, evolving into something else or becoming extinct, with some of them living alongside other hominin species ancestral to humans for tens of thousands of years before succumbing to the selective pressures of ecological upheaval. (It appears, for example, that Homo ergaster, sometimes referred to as “African H. erectus,” H. habilis, and the robust australopithecine Paranthropus boisei lived together in some parts of Africa for this long.)
The first group of primates clearly ancestral to H. sapiens are the gracile australopithecines. Among them are Australopithecus afarensis, A. africanus, and A. sediba. They begin appearing in the fossil record in the early Pliocene, 4 to 5 million years ago, and several survive into the late Pliocene. One of them, possibly A. afarensis, is the likely progenitor of H. habilis. And H. habilis might conceivably be ancestral to H. erectus. Or H. erectus could be a descendant of a lineage yet to be discovered.
However he came to be, H. habilis is making stone tools by about 2.6 million years ago. H. erectus shows up about 1.89 million years ago, first as H. ergaster in Africa and later as H. erectus in eastern Asia. (A descendant of H. ergaster, H. heidelbergensis, is the probable progenitor of both H. neanderthalensis and H. sapiens.) H. erectus might have survived in eastern Asia until about 100,000 years ago, and H. floresiensis might be among its descendants. Homo floresiensis survives until about 54,000 years ago in southeast Asia.
Homo ergaster, who has fairly strong support among paleoanthropologists as H. sapiens’s earliest direct ancestor, is often the starting point today for a consideration of the one characteristic that finally radically differentiates H. sapiens from all other hominins: culture. (Bipedalism and a significant enough increase in brain size over australopithecines had been in place a long time among humanity’s close relatives.) By about 200,000 years ago or so, anatomically modern man is hunting and gathering and living a social life in Africa. H. neanderthalensis, perhaps descended from a different population of H. heidelbergensis than the African one, is doing the same in western Asia and Europe.
* * *
—
IT’S IMPORTANT TO NOTE here that each of these hominins appears in the fossil record at a time closely associated with dramatic climate change. Such ecological changes—in the amount of moisture available, for example, which in certain areas favors the survival of extensive forests or the spread of grasslands—might favor one hominin species over another; or these ecological changes might accelerate the evolution of a new hominin species, one better suited to the new climatic conditions.
With the arrival of behaviorally modern, or cognitively modern, H. sapiens about 55,000 years ago, culture begins to play a role in the evolution of man as important, eventually, as environment. In this sense, H. sapiens makes himself exceptional among all other animals in the late Pleistocene by becoming as strong a force himself in the process of evolution by natural selection as meiosis.4
The tendency of some to exaggerate our own importance as a species in the great theater of life on Earth is a sign of hubris. A more biologically informed or enlightened, and certainly secular, point of view is that man is better off viewing himself as a flawed rather than a potentially omnipotent creature, an animal with no more of a guaranteed future than any other animal. This perspective, some argue, that we are not the be-all and end-all, might eventually lead to better politics and to the development of more equitable social and economic systems worldwide. Still, H. sapiens—i.e., culturally advanced man—is exceptional. The provocative question is, Where will his exceptionalism take him?
Like all other creatures, biological man is evolving in response to both natural and anthropogenic selective pressures such as deforestation and ocean acidification, the latter of which will dramatically affect its supply of protein in the near future. Other selective pressures, like that from global climate change, are powerful enough to render certain of humanity’s responses to them, like technological innovation, irrelevant. Further, the culturally generated selective pressures now affecting human evolution have, since the start of the Industrial Revolution, become so significant they’ve caused the extinction of hundreds of other species and triggered the Sixth Extinction of biological life. Those same anthropogenic forces, operating alongside familiar natural forces, are now shaping the evolution of all Earthly life.
The alarming situation here for humanity is that H. sapiens, though it has asserted itself as the dominant species on Earth, is at the same time the potential victim of its domination over virtually all Earth’s ecosystems. If H. sapiens were to become extinct, the event would simply be regarded as evolution continuing to unfold, a biological future for life but not one that any longer included humanity.
It is worth noting as well that H. sapiens’s anatomical evolution, as measured today by genomics, has begun to accelerate. Among some evolutionists, this situation foreshadows speciation.
* * *
—
HAVING PUT FORTH this generalized and somewhat conjectural sketch of human origins, I c
an now situate, in a more meaningful way, what Kamoya and his colleagues were interested in finding during the time I spent with them around Nakirai. They were looking in particular for late Miocene/early Pliocene fossils in the larger hominid family, but they also hoped to find, for example, fossils in the developmental lines of the gracile and robust australopithecines. (In deposits this old, they were not likely to find the fossils of any species in the genus Homo.)
The interpretation of hominid fossils is a relatively circumscribed pursuit. The research consists almost entirely of examining and reexamining a relatively small collection of fossils. Most interpretations of the evidence represent responses to straightforward and long-established questions about anatomy and phylogeny. Each new fossil amplifies or refines what we know, and of course the physical evidence itself has tremendous authority. It is in the allied nascent field of evolutionary psychology, however, that the opportunity today for stunning insights into the evolution of human beings now seems to be much greater, because of recent advances in neuroscience. And it is also here that speculation, formal theorizing, and laboratory research are likely to create a broader and more informed public debate than human evolutionary biology has had to face in the past from the very large number of people who do not believe in hominin evolution.
The more provocative interpretations of man’s history now no longer revolve around whether Australopithecus sediba or A. afarensis is directly ancestral to man but around the question of what happened to a single, relatively small group of H. sapiens living in the general vicinity of what is today Djibouti, in the Horn of Africa, about 55,000 years ago. A number of scientists lean toward the view that what occurred was a small change in the structure of the human brain, a minor encephalic event that would nevertheless prove to be extraordinarily adaptive, and which probably accounts for the sudden appearance at this time of stunningly complex human cultures. The Middle Paleolithic, which began about 120,000 years before with H. sapiens making stone tools far more sophisticated than H. erectus’s tools, ends here, and the Upper Paleolithic begins. Keeping track of human origins now requires classifying H. sapiens not by changes in his anatomy but by the development of increasingly rich and diverse regional cultures.