Leonardo’s Mountain of Clams and the Diet of Worms (27 page)

The out-of-Africa alternative may best be understood as a particular version of the bushy perspective.
Homo erectus
moves out to all three Old World continents.
Homo sapiens
arises as a branch (the bushy view) from one of these populations, not as a terminus to a universal trend.
Homo sapiens
then spreads as a second diaspora from its place of origin, presumably Africa on both genetic and paleontological grounds. But
Homo erectus
(or its descendants) already inhabit Europe and Asia—so African
Homo sapiens
arrives as a second human species (bushy coexistence again), and eventually supplants the original form. Under this bushy view, Neanderthal and modern
Homo sapiens
are
separate (and potentially coexisting) human species, not the before and after of a single linear transformation—for Neanderthal branched from European
Homo erectus
(or its descendants), while forebears of modern Europeans arrived from Africa after a separate origin from African
Homo erectus
populations.

In my reading, and as summarized elsewhere (perhaps best in the recent book by C. Stringer
and R. McKie,
African Exodus: The Origin of Modern Humanity
), the balance of recent evidence tilts strongly (perhaps conclusively) to the out-of-Africa view, and therefore to the predominance of bushiness over linearity as a central theme in human evolution. (Incidentally, this new and emerging consensus is the very view that Brace so scornfully rejected and labeled as “hominid catastrophism”—the
idea that
Homo sapiens
arrived from Africa as a second wave and supplanted Neanderthal, in contrast with the only reconstruction that Brace regarded as “evolutionary,” that is, the linear passage of Neanderthal to modern humans. In fact, both views are equally consistent with an evolutionary perspective. The contingent and empirical data of actual history, not preferences of theory [laden with
a complex range of unconscious biases], must decide the issue.)

5.
M
ORE BUSHINESS IN LATER HUMAN HISTORY: NEW DATA FROM
A
SIA.
If Neanderthal and
Homo sapiens
coexisted as independent species in Europe, thus refuting the linear view, what happened in eastern Asia, where Dubois first discovered
Homo erectus
in the 1890s, and where this ancestral species enjoyed long and widespread success? In the
multiregional view, these Asian
Homo erectus
populations evolved directly into modern Asian groups of
Homo sapiens.
In the bushy alternative,
Homo sapiens
arrived (ultimately from Africa) as a second wave of migration, and may have coexisted for a time with Asian
Homo erectus
or its descendants. The obvious test between these starkly different views requires a fossil record, either of intermediacy
or of coexistence, during the crucial time of transition between the two species. But such decisive data have not been available, because the youngest known Asian
Homo erectus
(from China) range from about 290,000 to 420,000 years old, while the oldest Asian
Homo sapiens
specimens are only about 40,000 years old. Thus, we had no evidence at all for the crucial intervening years.

Eugen Dubois
first discovered
Homo erectus
in Java during the early 1890s—and these specimens, from Trinil, remain the most famous Indonesian representatives of the species. But, in the early 1930s, Dutch geologists discovered a suite of twelve hominid calvaria (skull tops lacking the facial skeleton and upper jaws) from the nearby site of Ngandong on the banks of the Solo River. These specimens—variously
known in the older literature as “Solo man” or
“Homo soloensis”
—have engendered a long and substantial debate about their identity, but a present consensus considers them as members of Dubois’s species,
Homo erectus.

Yet, while anthropologists had finally reached some agreement about their identity, the age of the Solo specimens remained unknown. This crucial issue may now have been resolved—and
in a surprising manner—by an article that appeared in the December 13, 1996, issue of
Science
magazine: “Latest
Homo erectus
of Java: Potential contemporaneity with
Homo sapiens
in Southeast Asia,” by C. C. Swisher III, W. J. Rink, S. C. Anton, H. P. Schwarcz, G. H. Curtis, A. Suprijo, and Widiasmoro (yes, the last author’s name is complete; most Indonesians, like former leader Suharto, or past
boss Sukarno, use only one name). The curators of the Solo calvaria would not let these authors use the original material for dating (since the methods destroy parts of the specimens). So Swisher and colleagues collected bovid teeth (cattle and their relatives) from two sites in the same stratum that yielded the hominid calvaria. They applied two independent techniques of radiometric dating, and
reached the same surprising conclusion—ever so gratifying for fans of the bush—that the Solo hominid specimens lived between 27,000 and 53,000 years ago. If these conclusions stand up to later scrutiny, then
Homo erectus
did not transform to modern humans in Asia—for the two species coexisted as independent entities about forty thousand years ago.

Moreover, and moving to the general statement
that inspired this essay, if we now consider the whole earth at forty thousand years ago, we note a bush of three coexisting human species—
Homo neanderthalensis
in Europe, surviving
Homo erectus
in Asia, and
Homo sapiens
continuing a relentless spread throughout the habitable world. This collection of three might not match the richness of an African bush of some half a dozen species about 2 million
years ago, but the conclusion that three human species still coexisted as recently as thirty to forty thousand years ago does require a major reassessment of conventional thinking. Our modern world represents the oddity, not the generality. Only one human species now inhabits this planet, but most of hominid history featured a multiplicity, not a unity.

I have focused this essay upon one of the
great unconscious biases—our persisting preference for viewing history as a tale of linear progress—that so often stymie our interpretations of evolution and the history of life on Earth. But we should also recognize this other, rather more “homey” or obvious bias—our tendency to view a comfortable and well-known current situation as a generality rather than a potential exception. Such an attitude
also has a highfalutin name in the history of science—
uniformitarianism
, or using the present as a key to the past.

As many scholars have pointed out (including yours truly in his very first published paper of 1965), uniformitarianism is a complex term with multiple meanings, some legitimate, but some potentially false and surely constraining. If we only mean that we will regard nature’s laws
as invariant in space and time, then we are simply articulating a general assumption and rule of reasoning in science. But if we falsely extend such a claim to current
phenomena
(rather than universal
laws
)—and argue, for example, that continents must always be separated because oceans now divide our major landmasses, or that mass extinction by meteoritic bombardment cannot occur because we have
never witnessed such an event during the short span of recorded human history—then we surely go too far. The present range of observed causes and phenomena need not exhaust the realm of past possibilities.

In this case, we shall be massively and seriously fooled if we extrapolate a current reality to a general situation in the history of human evolution. Most of hominid history has featured a
bush, sometimes quite substantial, of coexisting species. The current status of humanity as a single species, maximally spread over an entire planet, is distinctly odd.

But if modern times are out of joint, why not make the most of it? I last visited Africa more than ten years ago, and that voyage (to lecture in Nairobi and do some fieldwork with Richard Leakey at Lake Turkana) led to some musings
that culminated in an essay titled “Human Equality Is a Contingent Fact of History.” I argued that the happenstance of a surprisingly recent common ancestry for all modern humans had made our so-called races effectively equal in biological capacities (while individuals within all groups differ widely, of course).

I couldn’t help revisiting this theme as I surveyed many sites of human hope, disappointment,
and struggle in Kenya, Malawi, and Zimbabwe. (I went to Africa in my role as a trustee of the Rockefeller Foundation, and we visited many of their social, medical, and agricultural projects—including a clinic for treating sexually transmitted diseases among prostitutes in one of the worst slums in Nairobi, and a series of schemes to improve corn yields in desperately poor agricultural
villages of Malawi.)

In the most memorable event of this trip, we spent an entire morning talking with the women farmers of a small Malawian village. This ample time gave us leisure to explore in depth, and to listen and observe with great care. My mind wandered over many subjects, but I kept returning to a single theme. I could not imagine a greater difference between earthly communities—a senior
American Ivy League professor, and an illiterate Malawian farmer, twenty-five years old, with five children (the oldest already eleven), and an annual family income of about eighty dollars. Yet her laughter, her facial expressions, her gestures, her hopes, her fears, her dreams, her passions, are no different from mine. One can understand the argument for human unity in a purely intellectual
and scientific sense, but until this knowledge can be fleshed out with visceral experience, one cannot truly know in the deeper sense of compassion.

If our current times are peculiar in substituting the bushy richness of most human history with an unusual biological unity to undergird our fascinating cultural diversity, why not take advantage of this gift? We didn’t even have such an option during
most of our tenure on Earth, but now we do. Why, then, have we more often failed than succeeded in the major salutary opportunity offered by our biological unity? We could do it; we really could. Why not try sistership; why not brotherhood?

IV

OF
H
I
STORY
AND
TOLER
A
TION

A
CERION
FOR CHRISTOPHER

I
F
C
HINA HAD PROMOTED, RATHER THAN INTENTIONALLY SUPPRESSED, THE
technology of oceanic transport and navigation, the cardinal theme for the second half of our millennium might well have been eastward, rather than westward, expansion into the New World. We can only speculate about the enormously different consequences of such an alternative but unrealized history.
Would Asian mariners have followed a path of conquest in the Western sense? Would their closer ethnic tie to Native Americans (who had migrated from Asia) have made any difference in treatment and relationship? At the very least, I suppose, any modern author of a book printed on the American East Coast would be writing this chapter either in a Native American tongue or in some derivative of Mandarin.

But China did not move east, so Christopher Columbus sailed west, greedy to find the gold of Cathay and the courts of the grand Khan as described by his countryman Marco Polo, who had traveled by different means and from the other direction. And Columbus encountered an entire world in between, blocking his way.

I can think of no other historical episode more portentous, or more replete with both
glory and horror, than the Western conquest of America. Since we can neither undo an event of such magnitude nor hope for any simple explanation as an ineluctable consequence of nature’s laws, we can only chronicle the events as they occurred, search for patterns, and seek understanding. When dense narrative of this sort becomes a primary method of analysis, detail assumes unusual importance.
The symbolic beginning must therefore elicit special attention and fascination. Let us therefore take up an old and unresolved issue: Where did Columbus unite the hemispheres on October 12, 1492?

Surrounded by hints of nearby land, yet faced with a crew on the verge of rebellion, Columbus knew that he must soon succeed or turn back. Then, at 2:00 A.M. on the morning of October 12, the
Pinta
’s
lookout, Rodrigo de Triana, saw a white cliff in the moonlight and shouted the transforming words of human history:
“Tierra! Tierra!”
—land, land. But what land did Columbus first see and explore?

Why should such a question pose any great difficulty? Why not just examine Columbus’s log, trace his route, look for artifacts, or consult the records of people first encountered? For a set of reasons,
both particular and general, none of these evident paths yields an unambiguous answer. We know that Columbus landed somewhere in the Bahama Islands, or in the neighboring Turks and Caicos. We also know that the local Taino people called this first landfall Guanahani—and that Columbus, kneeling in thanks and staking his claim for the monarchs of Spain, renamed the island San Salvador, or Holy Savior.
But the Bahamas include more than seven hundred islands, and several offer suitable harbors for Columbus’s vessels. Where did he first land?

Navigation, in Columbus’s time, was far too imprecise an art to provide much help (and Columbus had vastly underestimated the earth’s diameter, thereby permitting himself to believe that he had sailed all the way to Asia). Mariners of the fifteenth century
could not determine longitude, and therefore could not locate themselves at sea with pinpoint accuracy. Columbus used the two primary methods then available. Latitude could be determined (though only with difficulty on a moving ship) by sighting the altitude of Polaris (the North Star), or of the sun at midday. A ship could therefore sail to a determined latitude and then proceed either due east
or west, as desired. (Columbus, in fact, was a poor celestial navigator, and made little use of latitudes. In one famous incident, he misidentified his position by nearly twenty degrees because he mistook another star for Polaris.)