Wired for Culture: Origins of the Human Social Mind (18 page)

If our societies have for millennia been sorting us by our talents, even if weakly so, this is something society might benefit from knowing about. Most of us would agree that a society that promotes “equality of opportunity” is a desirable one. But we must also recognize that if there are inherent differences among individuals that make them more or less suited to a particular role or job in society, an inevitable consequence of equality of opportunity is to produce a society differentiated by innate predispositions, a
genetic meritocracy
. It will produce this meritocracy because equality of opportunity merely ensures that everyone has a fair chance of being delivered to the doorstep of a job or role in society, but does not ensure that everyone has an equal chance of being good at those roles. Inevitably, then, and the more so the greater the equality of opportunity, competition with others will sort people by their genetic predispositions. Or, as the sociologist Peter Saunders has written, the “essence of a meritocratic society is that it offers individuals equal opportunities to become unequal. There is open competition for the most desirable, responsible and well-rewarded positions, and the most able and committed people generally succeed in attaining these positions.”

CULTURE AND THE SELECTION OF OUR GENES

WHAT
is
staring us in the face is that there is now striking evidence that, coinciding with the advent of culture, our genes appear to have undergone an exceptionally rapid rate of adaptive evolution. This could, as mentioned, be evidence that recently evolved genes are still moving through our populations, but it could also mean that culture has been sorting us—the genetic phenomena themselves do not as yet clearly distinguish between these two alternatives. The evidence pointing to an increase in rates of evolution exploits the fact that our genes are arrayed on long strings of DNA called
chromosomes
. Humans have twenty-three pairs of chromosomes, one of each pair inherited from the mother and one from the father. This means that each of us has two copies of most genes, called
alleles
. The alleles might be the same or slightly different versions of the same genes. You might, for example, inherit a gene for brown eyes from your mother and blue eyes from your father. At another place along the same chromosome, you might have inherited a gene for long fingers from your mother but a gene for short fingers from your father. Now, if one allele of a gene—say blue eyes—is always found in combination with some other allele for a different gene—say short fingers—this tells us natural selection has acted strongly and quickly on that region of the chromosome to cause what is called a
linkage
between the two alleles. It is merely a physical linkage, not necessarily having anything to do with what these genes are for.

The reason that linkage identifies strong natural selection is that our pairs of chromosomes (the maternal and paternal copies) sometimes exchange some genes between them when we produce egg or sperm cells. Eggs and sperm carry just half our genes, and they are a random assortment of our maternal and paternal alleles. As a baby, you might have inherited the blue eyes and short fingers alleles from your father, but later in life one of these alleles might get exchanged with the alleles you inherited from your mother when you produce sperm or eggs. The process, known as
recombination
, occurs infrequently, so the probability of it splitting up a given pair of genes is low. This means that if something can propel a gene through a population rapidly it may come to be inherited by everyone before recombination has had a chance to separate it from other genes on that chromosome. That force is of course natural selection, and when it strongly favors an allele—because the allele confers a large advantage to survival and reproduction—the genes on this chromosome will become linked: they become more likely to be found together than expected for genes not undergoing strong selection.

When researchers study blocks of human DNA, they find thousands of linked genes that appear to have been subject to strong forces of natural selection. It is possible to attach estimates of the timings of these events of evolution, and the conclusion is that humans began to experience unusually rapid evolutionary changes to many of their genes beginning sometime around 40,000 years ago. One possibility is that this represents the limit of how far back in time this kind of genetic analysis can go. But the period beginning 40,000 years ago is also the period coinciding with the rapid expansion of human cultural groups around the world and with a flowering of human cultural innovations. It is possible, then, that the blocks of linked regions could be the signature of culture ushering us into different roles within our societies that favored particular combinations of genes. On the other hand, these strongly linked regions could just be the signature of widespread adaptation of entire groups of people to new environments. Forty thousand years ago was a time when humans were spreading out around the world, adapting to hot and cold climates, to new diets, and fossils show it was a time of rapid changes to our body size and shape. There were also new diseases such as smallpox, malaria, and yellow fever. Genes for brain size, pigmentation, immune responses, olfaction, nervous system regulation, and body size and shape all show signs of changing around this time. One intriguing finding is that genes associated with hearing seem also to have been subject to strong effects of natural selection. This could reflect the increasing importance in human societies of language and communication.

So, with current knowledge, we can’t say much more than that our genes have been undergoing strong selection in recent times, but another feature of our societies also leads us to believe that latent differences among us might still be being revealed. Human population sizes have been increasing over the last 40,000 years. Natural selection operates more efficiently in larger populations because when populations are small, chance or random events from one generation buffet the population of genes, making it hard for natural selection to pick out the varieties it prefers. This is the phenomenon of random drift discussed in Chapter 1. Equally it will be less effective at removing other varieties that are less beneficial. This means that the small early human populations might have carried many different genetic varieties owing to random genetic drift. These varieties—sometimes referred to as evolutionary
debris
—would have been increasingly revealed to the honing effects of natural selection as populations grew. In the presence of cultural opportunities and larger groups, what was once debris might have become the raw materials of our differences.

Some of this debris may surface in the modern world in unexpected ways. Dyslexia is a heritable condition often associated with difficulties in reading and writing. It might have gone unnoticed before the emergence of writing because it did not affect any capabilities that mattered, and it is even possible that it granted some benefit in times past. For instance, we know that in modern society many dyslexics are good at mathematics, spatial reasoning, and computer programming. Autistic people often have profound deficits in understanding others’ motives and feelings, can be infuriatingly literal-minded, and are often socially withdrawn and isolated from others. Autism is also heritable and about four times more common in boys than girls. The psychologist Simon Baron-Cohen suggests that autism might represent the extreme end of a normal continuum of abilities to focus on and single-mindedly persevere at a task to the exclusion of others—he calls it the
extreme male brain
. The dispositions that produce the extreme male brain might have been useful in our evolutionary past, for tasks such as warfare or hunting large game that might demand a concentrated and unempathetic commitment to tracking down and then executing one’s prey. Baron-Cohen also suggests that boys might be more prone to what he terms
systemizing
, and this is seen in hobbies such as collecting things, bird-spotting, repairing cars and motorbikes, becoming a pilot, or sailing, but also in interest in mathematics and computer games and computer programming.

In our current environment, autism is an awkward condition and at its worst it can be disabling. The brilliant early twentieth-century physicist Paul Dirac is sometimes compared to Einstein for the intellectual depth of his discoveries. Dirac was also autistic, and some biographers speculate that his single-mindedness and ability to shut out or not even be aware of those around him might have benefitted his scientific work. Dirac was awkward and he would exasperate colleagues by not speaking for days. He would often go on long country bicycle rides with his daughter and not utter a word. One time after giving a lecture he agreed to take questions and a man raised his hand to say he didn’t understand the equation in one of Dirac’s slides. Dirac stood motionless for about a minute and a half, at which point the moderator asked him if he was going to answer the question. Dirac replied that it wasn’t a question.

THE PUSH OF OUR GENES AND THE GENTLE PULL
OF THE FUTURE

TO SOME,
the idea that cultural innovations unlock differences among us that quietly await their destinies in finding a task or role they are good at might suggest that we have been on a preordained trajectory, an unfurling, or inevitable march to modernity. Some social anthropologists see in this a tendency to believe there is an inherent superiority to modern society, it being further along the path of inevitable progress. But this is a view that confuses different senses of the idea of progress. Cultural evolution has produced increased technological complexity, and most would probably agree it has raised our standards of living, even if unequally so around the world. If improved health and well-being makes modern societies superior, then these social anthropologists are correct, but then again one would not wish to see this as a bad thing. Biological evolution has also been progressive in this sense of producing greater complexity. The first life, starting billions of years ago, comprised simple, single-celled organisms; only later did natural selection discover how to build big, complex things like elephants.

But neither cultural nor biological evolution has been progressive in the sense of working toward some predetermined or preordained goal. Both merely lumber along producing new varieties of things, some of which catch on and some of which don’t. Nevertheless, we might have to accept that there is at least some broad inevitability to the outcomes of both cultural and natural selection. Given the physical nature of our planet, were we to rerun the tape of biological evolution it is highly likely the plants would evolve again, and if they did, it is highly likely we would see things like birds, fish, and land animals evolving to make use of the oxygen they released. These new forms might not be identical to the ones we have now, but there is good reason to expect that the broad outlines would reemerge. We know this because evolution has already played the tape independently many times on the plants and animals we do have. Penguins, seals, otters, porpoises, and fish have all independently evolved similar streamlined shapes for coursing through water. Birds, insects, bats, and some fish have all evolved wings for flight. Consider that in any world that produced insects that flew in the air, it is highly likely something like a bat or insect-eating bird would evolve to catch them. And if trees evolved, things would evolve to climb them, or giraffelike, acquire long legs and necks to eat their upper leaves.

Whether another sentient being like ourselves would reappear is impossible to know, but we do know that there is no reason to rule it out. The sentient being that walks this planet is upright, bipedal, naked, has superb eye-hand coordination, good color eyesight, highly dexterous hands, and is capable of social learning. I suspect that were we able to replay our cultural evolution, we would get many of the same things we have now, because our cultures will always have had a tendency to come up with and retain innovations that we are good at using or good at exploiting. This is an obvious point, but it is easy to forget how much it determines the cultural innovations we see around us today and that we developed throughout our history. Wheels were invented several times independently in different parts of the world, as were stone tools, clothes, spears, bows and arrows, atlatls (spear throwers), boats, shelters, agriculture, and fishing technologies.

The nature of our physical world and of our bodies makes not just these inventions but even the forms they took nearly inevitable. For example, bicycles were invented sometime in the nineteenth century, and their principles have remained unchanged since. They were probably destined to be part of our societies from the moment we first emerged as modern humans, having only to await the equally inevitable accumulation of the metallurgical and other technologies that made them possible. So, too, perhaps were hammers, steam engines, airplanes, toasters, and computers. For the same reason there are probably also some things that, if we thought hard enough, we could rule out will ever be a part of our societies. Strap-on wings, telepathy machines, and color television programs in the ultraviolet spectrum have never caught on and probably never will because none exploits our innate abilities.

Uniquely in the case of our species, this interplay between our genes pushing us toward particular outcomes and our cultures producing technologies that respond to our talents means that the goalposts of our existence are constantly being shifted. But even the shifting is somewhat predictable because it must fit in with what we are disposed to want to do and are capable of doing, and so cultural developments merely reduce the demand for old skills, while raising it for others. Increasingly, there is little need for the backbreaking physical labor that might have built our modern societies, and so little need for the physiques that did this work. Instead, the modern world will call for a more domesticated set of abilities, among them mental agility, concentration, and communication skills. Culture has not yet finished sorting us by our talents.