The Meaning of Human Existence (2 page)

2

Solving the Riddle of the Human Species

T
o grasp the present human condition it is necessary to add the biological evolution of a species and the circumstances that led to its prehistory. This task of understanding humanity is too important and too daunting to leave exclusively to the humanities. Their many branches, from philosophy to law to history and the creative arts, have described the particularities of human nature back and forth in endless permutations, albeit laced with genius and in exquisite detail. But they have not explained why we possess our special nature and not some other, out of a vast number of conceivable natures. In that sense, the humanities have not achieved nor will they ever achieve a full understanding of the meaning of our species’ existence.

So, as best we can answer, just what are we? The key to the great riddle lies in the circumstance and process that created our species. The human condition is a product
of history—not just the six millennia of civilization but very much further back, across hundreds of millennia. The whole of it, biological and cultural evolution, must be explored in seamless unity for a complete answer to the mystery. When viewed across its entire traverse, the history of humanity also becomes the key to learning how and why our species arose and survived.

A majority of people prefer to interpret history as the unfolding of a supernatural design, to whose author we owe obeisance. But that comforting interpretation has grown less supportable as knowledge of the real world has expanded. Scientific knowledge in particular, measured by numbers of scientists and scientific journals, has been doubling every ten to twenty years for over a century. In traditional explanations of the past, religious creation stories have been blended with the humanities to attribute meaning to our species’ existence. The time has come to consider what science might give to the humanities and the humanities to science in a common search for a more solidly grounded answer than before to the great riddle of our existence.

To begin, biologists have found that the biological origin of advanced social behavior in humans was similar to that occurring elsewhere in the animal kingdom. Using comparative studies of thousands of animal species, from insects to mammals, we’ve concluded that the
most complex societies have arisen through eusociality—meaning, roughly, the “true” social condition. By definition, the members of a eusocial group cooperatively rear the young across multiple generations. They also divide labor through the surrender by some members of at least part of their personal reproduction in a way that increases the “reproductive success” (lifetime reproduction) of other members.

Eusociality stands out as an oddity in a couple of ways. One is its extreme rarity. Out of hundreds of thousands of evolving lines of animals on the land during the past four hundred million years, the condition, so far as we can determine, has arisen only nineteen times, scattered across insects, marine crustaceans, and subterranean rodents. The number is twenty, if we include human beings. This is likely to be an underestimate, perhaps a gross one, due to sampling error. Nevertheless, we can be certain that the number of originations of eusociality was relatively very small.

Furthermore, the known eusocial species arose very late in the history of life. It appears to have occurred not at all during the great Paleozoic diversification of insects, 350 to 250 million years before the present, during which the variety of insects approached that of today. Nor is there as yet any evidence of eusocial species alive during the Mesozoic Era until the appearance of the
earliest termites and ants between 200 and 150 million years ago. Humans at the Homo level appeared only very recently, following tens of millions of years of evolution among the Old World primates.

Once attained, advanced social behavior at the eusocial grade found a major ecological success. Of the nineteen known independent lines among animals, just two within the insects—ants and termites—globally dominate invertebrates on the land. Although they are represented by fewer than twenty thousand of the million known living insect species, ants and termites compose more than half of the world’s insect body weight.

The history of eusociality raises a question: Given the enormous advantage it confers, why has this advanced form of social behavior been so rare and long in coming? The answer appears to be the special sequence of preliminary evolutionary changes that must occur before the final step to eusociality can be taken. In all of the eusocial species analyzed to date, the final step before eusociality is the construction of a protected nest, from which foraging trips are launched and within which the young are raised to maturity. The original nest builders can be a lone female, a mated pair, or a small and weakly organized group. When this final preliminary step is attained, all that is needed to create a eusocial colony is for the parents and offspring to stay at the nest
and cooperate in raising additional generations of young. Such primitive assemblages then divide easily into risk-prone foragers and risk-averse parents and nurses.

What brought a single primate line to the rare level of eusociality? Paleontologists have found that the circumstances were humble. In Africa roughly two million years ago, one species of the primarily vegetarian australopithecines evidently began to shift its diet to include a much higher reliance on meat. For a group to harvest such a high-energy, widely dispersed source of food, it did not pay to roam about as a loosely organized pack of adults and young in the manner of present-day chimpanzees and bonobos. It was more efficient to occupy a campsite (thus, the nest) and send out hunters who could bring home meat, both killed or scavenged, to share with others. In exchange, the hunters received protection of the campsite and their own young offspring kept there.

From studies of modern humans, including hunter-gatherers, whose lives tell us so much about human origins, social psychologists have deduced the mental growth that began with hunting and campsites. A premium was placed on personal relationships geared to both competition and cooperation among the members. The process was ceaselessly dynamic and demanding. It far exceeded in intensity anything similar experienced by the wide-roaming, loosely organized bands of most
animal societies. It required a memory good enough to assess the intentions of fellow members, as well as to predict their responses from one moment to the next, and, of decisive importance, it required the ability to invent and inwardly rehearse competing scenarios of future interactions.

The social intelligence of the campsite-anchored prehumans evolved as a kind of nonstop game of chess. Today, at the terminus of this evolutionary process, our immense memory banks are smoothly activated to join past, present, and future. They allow us to evaluate the prospects and consequences of alliances, bonding, sexual contact, rivalries, domination, deception, loyalty, and betrayal. We instinctively delight in the telling of countless stories about others, cast as players upon our own inner stage. The best of it is expressed in the creative arts, political theory, and other higher-level activities we have come to call the humanities.

The definitive part of the long creation story evidently began with the primitive
Homo habilis
(or a species closely related to it) two million years ago. Prior to the habilines the prehumans had been animals. Largely vegetarians, they had humanlike bodies, but their cranial capacity remained chimpanzee-sized, at or below 600 cubic centimeters (cc). Starting with the habiline period the capacity grew precipitously, to 680cc in
Homo habilis
,
900cc in
Homo
erectus
, and about 1,400cc in
Homo
sapiens
. The expansion of the human brain was one of the most rapid episodes of complex tissue evolution in the history of life.

Yet to recognize the rare coming together of cooperating primates is not enough to account for the full potential of modern humans provided by a large brain capacity. Evolutionary biologists have also searched for the grand master of advanced social evolution, the combination of forces and environmental circumstances that bestowed greater longevity and more successful reproduction upon the possessors of high social intelligence. Two competing theories of the principal force have been in contention. The first envisions kin selection: individuals favor collateral kin (relatives other than offspring), making it easier for altruism to evolve among members of the same group. Complex social behavior can evolve when group members individually reap greater benefits in numbers of genes passed to the next generation than losses from their altruism, averaged through their behavior toward all members of the group. The combined effect on the survival and reproduction of the individual is called inclusive fitness, and the explanation of evolution by it is called the theory of inclusive fitness.

In the second, more recently argued theory (full disclosure: I am one of the modern version’s authors), the
grand master is multilevel selection. This formulation recognizes two levels at which natural selection operates: individual selection based on competition and cooperation among members of the same group, and group selection, which arises from competition and cooperation between groups. Group selection can occur through violent conflict or by competition between groups in the finding and harvesting of new resources. Multilevel selection is gaining in favor among evolutionary biologists because of recent mathematical proofs that kin selection can operate only under special conditions that rarely if ever exist. Also, multilevel selection is easily fitted to all of the known real animal cases of eusocial evolution, whereas kin selection, even when hypothetically plausible, can be fitted less well or not at all. (I’ll treat this important subject in detail later, in
Chapter 6
.)

The roles of both individual and group selection are clear in the details of human social behavior. People are intensely interested in the minutiae of behavior of those around them. Gossip is a prevailing subject of conversation, everywhere from hunter-gatherer campsites to royal courts. The mind is a kaleidoscopically shifting map of others inside the group and a few outside, each of whom is evaluated emotionally in shades of trust, love, hatred, suspicion, admiration, envy, and sociability. We are compulsively driven to belong to groups or to create
them as needed, which are variously nested, or overlapping, or separate, and in addition ranging from very large to very small. Almost all groups compete with those of similar kind in some manner or other. However gently expressed and generous in the tone of our discourse, we tend to think of our own group as superior, and we define our personal identities as members within them. The existence of competition, including military conflict, has been a hallmark of societies as far back in prehistory as archaeological evidence can be brought to bear.

The major features of the biological origins of
Homo sapiens
are coming into focus, and this clarification raises the potential of a more fruitful contact between science and the humanities. The convergence between these two great branches of learning will matter hugely when enough people have thought its potential through. On the science side, genetics as well as the brain sciences, evolutionary biology, and paleontology will each be seen in a different light. Students will be taught prehistory as well as conventional history, and the whole properly presented as the living world’s greatest epic.

Pride and humility in better balance, we’ll also take a more serious look at our place in nature. Exalted we are, risen to be the mind of the biosphere without a doubt, our spirits uniquely capable of awe and ever more breathtaking leaps of imagination. But we are still part
of Earth’s fauna and flora, bound to it by emotion, physiology, and, not least, deep history. It is folly to think of this planet as a way station to a better world. Equally, Earth would be unsustainable if converted into a literal, human-engineered spaceship.

Human existence may be simpler than we thought. There is no predestination, no unfathomed mystery of life. Demons and gods do not vie for our allegiance. Instead, we are self-made, independent, alone, and fragile, a biological species adapted to live in a biological world. What counts for long-term survival is intelligent self-understanding, based upon a greater independence of thought than that tolerated today even in our most advanced democratic societies.

3

Evolution and Our Inner Conflict

A
re human beings intrinsically good but corruptible by the forces of evil, or the reverse, innately sinful yet redeemable by the forces of good? Are we built to pledge our lives to a group, even to the risk of death, or the opposite, built to place ourselves and our families above all else? Scientific evidence, a good part of it accumulated during the past twenty years, suggests that we are both of these things simultaneously. Each of us is inherently conflicted. Team player or whistle-blower? Charitable donation or personal certificates of deposit? Admitted traffic violation or denial? I don’t believe I can let this subject pass by leaving my own conflicted emotions unconfessed. When Carl Sagan won the Pulitzer Prize for nonfiction in 1978, I dismissed it as a minor achievement for a scientist, scarcely worth listing. When I won the same prize the following year, it wondrously
became a major literary award of which scientists should take special note.

We are all genetic chimeras, at once saints and sinners, champions of the truth and hypocrites—not because humanity has failed to reach some foreordained religious or ideological ideal, but because of the way our species originated across millions of years of biological evolution.

Don’t get me wrong. I am not implying that we are driven by instinct in the manner of animals. Yet in order to understand the human condition, it is necessary to accept that we do have instincts, and it will be wise to take into account our very distant ancestors—as far back and in as fine a detail as possible. History alone cannot reach this level of understanding. It stops at the dawn of literacy, where it turns the rest of the story over to the detective work of archaeology. In still deeper time the quest becomes paleontology. For the real human story, history must comprise both the biological and cultural.