Everyone Is African (17 page)

The most reliable compilations of data are those that identify major trends among exceptionally large numbers of people over decades of time. One such
trend is known as the
Flynn effect
, named after psychologist James R. Flynn of the University of Otago in New Zealand. His own words best describe it: “‘The Flynn Effect' is the name that has become attached to an exciting development, namely, that the twentieth century saw massive IQ gains from one generation to another.”
⁴²

These gains are evident in essentially every country where IQ tests have been administered long enough to detect a trend—thirty countries as of 2012.
⁴³
In countries that had been modernized by the beginning of the twentieth century, the gains have averaged approximately three IQ points per decade.
⁴⁴
Less developed countries have also almost universally experienced gains.
⁴⁵
These gains, however, appear to be peaking in the most highly developed countries, such as Sweden. According to the 2012 review article by Nisbett and colleagues (one of whom is Flynn), “If Sweden represents the asymptote that we are likely to see for modern nations' gains, the IQ gap between developing and developed nations could close by the end of the 21st century and falsify the hypothesis that some nations lack the intelligence to fully industrialize.”
⁴⁶

As psychologists and geneticists have pointed out, genetic changes over so short a period are insufficient to explain the Flynn effect, and, therefore, changing environments must be its principal cause. A number of environmental causes have been proposed, such as improvements in nutrition and education. Notably, the gains are not equivalent across the board but are, in most cases, greatest among groups of people who historically have scored lowest on IQ tests, and scores dramatically improve as economic and educational status improves. According to Nisbett and colleagues, “It seems likely that the ultimate cause of IQ gains is the Industrial Revolution, which produced a need for increased intellectual skills that modern societies somehow rose to meet.”
⁴⁷
Flynn, as a coauthor, agreed, but he also proposes a more specific explanation consistent with the Industrial Revolution and changes in education. He notes that gains are not evenly distributed across the subject areas that IQ tests measure but, instead, are greatest for analytical reasoning and pattern recognition and lowest for basic arithmetic. Education during the latter part of the twentieth century has placed greater emphasis on logic and abstract reasoning, mirroring the areas of IQ for which nations experienced
the greatest gains.
⁴⁸

Perhaps the most serious deficiency for arguments supporting hereditarianism, especially racial hereditarianism, is the fact that nearly all measurements of genetic variation for IQ have been indirect. Genetic variation has been assigned essentially by default, under the presumption that any variation unexplained by environment must be genetic. One of the greatest advances in human genetics in recent years is the ability to measure genetic variation
directly
by tracking variants in DNA. In previous chapters, we've already seen how direct detection of variants in DNA can explain genetic variation for skin, hair, and eye pigmentation; inherited conditions; and susceptibility to a wide range of diseases, both infectious and noninfectious.

The ultimate confirmation of the underlying genetic influence on variation for any human trait is identification of causal variants in DNA. In the late 1990s, a number of psychologists expressed hope that genes and variants governing variation for intelligence would soon be identified.
⁴⁹
However, in spite of much research, identification of such genes and variants has proven elusive. Robert Plomin of King's College London has contributed some of the most significant research on variation for IQ, particularly through large-scale and long-term twin studies in the United Kingdom. In a 2013 article, Plomin laments that predictions made in the late 1990s regarding gene identification were “overly optimistic.”
⁵⁰
He also refers to the problem of
missing heritability
, defined as failure to confirm heritability estimates with DNA analysis:

Genetic designs such as the twin method would no longer be needed if it were possible to identify all of the genes responsible for heritability. However, it has proven more difficult than expected to identify genes for complex traits, including
g
, which has led to the refrain of “missing heritability.”
⁵¹

During the first decade of the twenty-first century, a few genes and variants were identified as being associated with variation for intelligence. However, in 2011, a group of sixteen scientists representing institutions in the United States and Europe published a large-scale study that attempted to confirm these associations. They phrased the title of their article as a sentence, which aptly summarizes their main conclusion: “Most reported genetic associations with general intelligence are probably false positives.”
⁵²

Thus far, no single variant in any gene has been definitively associated with variation for IQ or
g
. However, when multiple variants are examined in the aggregate, a statistically detectable association with IQ and
g
has been identified. However, each variant appears to have no more than a very minor effect on variation for IQ or
g
. Only when many variants are examined in large numbers of individuals in the aggregate can a genetic influence on variation for IQ and
g
be detected.

Although large-scale studies on DNA variants and their relationship to IQ and
g
are relatively recent and few, a consensus on two major points appears to be emerging. First, variation for IQ and
g
is heritable to some degree, with heritability estimates differing among the populations studied.
⁵³
In this sense, direct estimates of genetic variation based on DNA studies are consistent with earlier studies relying on indirect estimates, which likewise produce varying heritability estimates. Second, no single gene or variant appears to have a major effect on variation for IQ or
g
. Instead, a large number of DNA variants, each with a very minor effect, combine in complex ways to influence variation for IQ and
g
. Adding to this complexity is the significant and often-changing influence of environmental variation.

That variation for intelligence is probably heritable to some degree has never been in question, even from the staunchest opponents of hereditarianism. Gould, for instance, wrote in
The Mismeasure of Man
,

The hereditarian fallacy is not the simple claim that IQ is to some degree “heritable.” I have no doubt that it is, though the degree has clearly been exaggerated by the most avid hereditarians. It is hard to find any broad aspect of human performance or anatomy that has no heritable component at all.
⁵⁴

Instead, the principal, and most controversial, question is whether average differences in IQ between so-called racial or ethnic groups can be attributed to genetic differences between these groups. DNA studies have thus far provided little clarification on this question. The vast majority of people who were the subjects of DNA-based studies were drawn from populations of predominantly European ancestry (mostly from the United Kingdom, Australia,
the Netherlands, and the United States).
⁵⁵
The failure to identify any variants with major effects makes it difficult to extend the results of these studies to more ancestrally diverse populations.

Much of human genetic variation consists of ancient African variation. The inference that genetic variants influencing human intelligence are numerous, each with a very small effect, further suggests that most of these variants are dispersed throughout humanity rather than concentrated in people with a particular ancestral background. The fact that DNA studies on IQ and
g
have yet to include large numbers of people with highly varied ancestry means there currently is no direct DNA evidence supporting the claim that average differences between ethnically defined groups have a genetic basis. And, given what
is
known about the predominantly ancient African nature of the majority of human genetic diversity, such evidence is unlikely to be discovered. Concurrently, there is abundant evidence that a host of nongenetic factors influence variation for IQ and
g
. The Flynn effect, in particular, provides definitive historical evidence that large gains are possible when overall economic and educational conditions improve.

Current scientific evidence fails to support hereditarian arguments against public investment in education and programs that benefit the economically disadvantaged. There is ample evidence that investment in education yields economic benefits that derive from a well-educated workforce. And there is no question that disparities for educational and economic opportunities have conferred substantial disadvantages to people in ethnic minorities—in the United States, especially African, Hispanic, and Native Americans—a fact readily acknowledged by even the most devout hereditarians.
⁵⁶

Yet, as I write this, disinvestment in public education has been underway for some time, from the preschool through higher-education levels. Head Start, a long-standing program in the United States to assist disadvantaged preschool children, suffered one of its largest cuts in 2013, depriving thousands of impoverished children of early educational intervention. Public schools have likewise suffered reductions in numbers of teachers, budgets for facilities and supplies, and educational programs. Public colleges and universities are especially hard hit as increasingly smaller proportions of their budgets come from public funding. As a professor and administrator at an open-enrollment
public university whose mission is to serve diverse groups of students, I have a firsthand sense of how seriously such disinvestment impacts student success.

These cuts cannot be attributed to the ideologies of hereditarians but, rather, the difficult choices politicians and government administrators must make when faced with competing demands for limited budgets. Nonetheless, the impact of educational disinvestment is the same regardless of the reason. Much of today's educational inequality is the legacy of historical racism. The affluence of one's family, the neighborhood in which one resides, and the educational background of one's parents all are major factors influencing educational opportunity and attainment. The historic roots of educational inequality lie in the history of racial segregation, and, inevitably, they continue to discriminate along socially defined lines of race, even if the intent to do so is a relic of the past. Recent trends of reversion to increased educational inequality prompted by budget woes disproportionally affect the disadvantaged, further exacerbate attainment gaps, and, tragically, erase gains that have started to close those gaps.

Not long ago, I had the privilege of traveling to northern Peru with a colleague who is a biological anthropologist. Our destination was the city of Lambayeque, where, at a nearby archaeological site, the remains of an elite woman who lived eight hundred years ago had been discovered and were being excavated. She was buried in a deep and elaborately decorated tomb near a colossal adobe pyramid. Her body had been draped in a blanket with dozens of copper medallions sewn into it. She wore layered pectoral necklaces on her chest: one made of copper ornaments, one of carved shell plates, another containing thousands of tiny colored beads meticulously fashioned from shell that had been strung together. Her arms bore bracelets of gold, and in one hand she held a gold scepter. A copper mask covered her face, and on her head was an ornate crown. Though her ears had long since decayed, it was apparent that the lobes had been gauged and stretched to hold exquisitely tooled gold earspools.

By then, all soft body tissue and fabric had deteriorated. All that remained were her teeth, the fragmented bones of her body, and the shell and metallic pieces of her ornamentation. On the forehead of her skull were traces of a bright vermilion pigment called cinnabar, a brilliantly colored but toxic mercury compound that had been smeared onto her face before burial. Accompanying her were six other skeletons: her consorts who had committed ritual suicide to join her in the afterlife. We do not know the name she had during her life; today, she is known as the
Sacerdotisa de Chornancap
(the Priestess of Chornancap).

At the time of our arrival, the rich ornamentation covering her body had been painstakingly removed and catalogued, exposing her fragmented skull (
figure 7.1
). I had the honor of reconstructing her facial features from the skull
fragments using forensic-sculpture methods. With the assistance of a student, I precisely replicated each fragment in three dimensions. Back in my studio in the United States, I assembled the replicated pieces and filled in missing sections with clay to reconstruct the skull. I placed prosthetic eyes in her eye sockets, then used colored clay to sculpt the muscles, tendons, ligaments, glands, fat, and skin. We then returned to Peru to complete the reconstruction with Peruvian colleagues from the museum that houses her remains. We gave her a wig of real human hair styled with bangs and braids, as women were depicted in the sculpted faces on pottery jars made during the time she lived. We dressed her with the ancient carved-shell beads of a pectoral necklace that had been restrung, along with her actual gold earspools (
figure 7.2
). A video of the process is at
https://www.youtube.com/watch?v=KxFBRFXxlmQ
.

Figure 7.1. Fragmented skull of an elite woman who governed the northern coastal region of what is now Peru approximately eight hundred years ago.
Photograph by Haagen Klaus; used with permission.

Figure 7.2. Forensic facial reconstruction of the Priestess of Chornancap, on display in the Hans Brüning National Archaeological Museum in Lambayeque, Peru.
Photographs by Daniel J. Fairbanks and Haagen Klaus; used with permission.

 

As I held the fragments of her skull in my gloved hands, I thought of my ancient kinship with her. Our shared ancestry was very distant, dating back at least thirty thousand years to people who lived probably somewhere near the Caucasus Mountains in west-central Asia. Our ancient ancestors diverged at that place long ago, hers migrating eastward, mine westward. People in her ancestral lineage traversed the continent of Asia over hundreds of generations to the ancient Isthmus of Beringia—connecting what are now northeast Russia and Alaska—and crossed into North America. Their descendants continued migrating southward through North America, some of them living probably no more than a day's drive of where I now live. Eventually, her still-distant ancestors reached the western shores of South America just south of the equator. Generations later, she was born and raised to be an elite ruler adored by her people. By then, my distant ancestors had migrated into Europe, where their descendants remained for millennia. When she was alive, all my ancestors were in northern Europe, many of them in England about the time when
the Magna Carta was written and sealed. They were entirely unaware the continent where she lived even existed. Eight centuries later, I was in Peru holding her remains, bringing her image back to life—my distant cousin separated by hundreds of years and thousands of generations.

Piecing together scientific information from ancient remains, historic accounts recorded during the Spanish conquest, and the native languages of modern people in the region, we now know much about her people and the civilizations that occupied that part of South America. The rich evidence reveals fascinating histories of people who migrated in and out of the region, prospered from agriculture and the sea, conducted mutually beneficial economic trade with other cultures, suffered from disease and climatic disasters, battled in war, and conquered or were conquered throughout millennia. The same can be said for ancient people in other parts of the world where abundant evidence has provided us with much information about their histories.

Today, we can add DNA analysis to the wealth of evidence from other sources to reconstruct the history of humanity. Most of the information from DNA comes from the modern descendants of people who lived long ago, although, in a few cases, DNA extracted from the remains of ancient people themselves has provided direct evidence of their genetic constitution. Moreover, DNA from the plant and animal species they domesticated and biogeographical information revealing how those species spread throughout the world offer additional evidence of ancient human history, migrations, and settlement. We are now at a point where we can combine information from Earth's climatic history, archaeology, anthropology, paleontology, plant and animal domestication, linguistics, and large-scale analysis of DNA to determine how humans populated the world and reconstruct the complexities of their ancient migrations. This history reveals how the ancestors of today's worldwide human population transitioned from hunter-gatherers to agriculturalists; how vast civilizations rose and fell; how some conquered others, taking over large regions; how factors such as climate change and infectious disease decimated certain populations, yet spared others; and how humans have moved (voluntarily or involuntarily) across and between continents, ultimately resulting in today's largest, most widespread, most mobile, most diverse, and most genetically complex population in human history.

An enormous amount of recent information became available with the development of laboratory methods that allow geneticists to examine hundreds of thousands of DNA variants simultaneously, generating massive data sets from which they reconstruct these histories. As a geneticist who has worked with these methods since the 1980s, I have experienced this astonishing progress firsthand.

Although the methods for analyzing these data sets are complex, the underlying premise is simple: All DNA variants originate as mutations that can happen in anyone at any time in any place. When a new variant originates, it is superimposed on a particular genetic background of nearby variants, and comparison of any variant with its background of nearby variants in DNA from people who are native to particular regions can help identify approximately when and where a particular variant originated.

The most advanced and comprehensive worldwide study of DNA variants to date was published in February 2014 by a group of geneticists and statisticians headed by Simon Myers of Oxford University. They examined 474,491 variants in 1,490 people from ninety-five populations sampled from around the world. Their analysis determined which human populations had contributed particular variants to other populations and approximately when those contributions happened on a worldwide scale. If one population contributes variants to another, the descendants in the recipient population are said to be
genetically admixed
, hence the title of their study: “A Genetic Atlas of Human Admixture History.”
¹

Both archaeology and DNA histories reveal that for most of human history, population sizes were relatively small, and migration events took hundreds to thousands of years, spanning many generations. Tens of thousands of years ago, human populations were slowly expanding into previously unoccupied parts of the world. Their weapons were crude, transportation was mostly by foot, and sustenance was from hunting and gathering. Skirmishes were relatively small and localized, without the wars and massive conquests typical of more recent human history. As new DNA variants arose, they accumulated in localized populations over many generations. Although older DNA variants had traveled far over tens of thousands of years and hundreds of generations, new DNA variants tended to remain localized to the regions where they originated, accumulating along with other variants against identifiable genetic backgrounds. To spread
far, they required long periods of time spanning numerous generations. These newer variants are the ancestry informative markers we've discussed in earlier chapters, each of which points to a particular part of the world as its ancestral source. Although most of human genetic variation is ancient African and is dispersed throughout humanity, by focusing on these more recent ancestry informative variants, scientists can decipher approximately when and where major human migration events took place.

According to these DNA studies, and congruent with recorded history, the localized distributions of these relatively recent variants began to change about four thousand years ago. Human mobility dramatically increased as the world's population size expanded, advanced civilizations emerged, long-range transportation technologies were invented, economic trade grew to an intercontinental scale, and large armies conquered people residing across vast regions. Newer variants that had previously been localized began spreading through major migration events, some dispersed to parts of the world very distant from their origins. As people who entered a distant region mated with those who were there, or took people from those regions back to their lands of origin, DNA variants became intermingled in their offspring and were permanently introduced into the offspring of people in different parts of the world.

“A Genetic Atlas of Human Admixture History,” together with several earlier studies focused on particular geographic regions, has uncovered strong evidence of more than a hundred of these genetic dispersal events, affecting the vast majority of the world's population, during the past four thousand years. One of the most significant is the Bantu expansion in sub-Saharan Africa, which intermingled variants carried by the migrating Bantu agriculturalists with the variants present in the highly diverse native populations of the African subcontinent. Another is the Mongol Empire, initiated by the conquests of Genghis Khan. At its peak in the thirteenth century, it spread from Asia's eastern shores to what is now Turkey in the west. Today, DNA variants carried by Mongol invaders remain intermingled with the variants that originated in these regions, along with ancient African variation. The Arab slave trade from the seventh through the nineteenth centuries brought slaves captured in Europe and Africa to the Middle East. The spread of variants went both ways: slave traders who lived in Europe and Africa left descendants, and
descendants of slaves taken to the Middle East were eventually integrated into the populations there. As a consequence, people from much of the Middle East carry African variants. The Arab conquest of north Africa began shortly after the death of Mohammed in 632 CE. Muslim armies consisting mostly of people from the Arabian Peninsula—but also converts to Islam from more distant regions, including Romans and Greeks—conquered Egypt and eventually spread into lands southward along the Nile River and westward along the Mediterranean coastline.
²
The genetic constitution of people throughout north Africa strongly bears the mark of this conquest. The Greek conquest of Alexander the Great during the fourth century BCE extended from Greece into Egypt in the south to what is now Pakistan in the east. The Roman Empire, at its peak in the second century CE, spread over nearly all of Europe and into the Middle East and north Africa, with the resulting dispersion of variants from Roman invaders throughout that empire. The Ottoman Empire, ruled from Constantinople (modern-day Istanbul), occupied much of what had been the eastern and southern Roman Empire, reaching its peak in the seventeenth century CE. And, last, European colonialism and the Atlantic slave trade were the most significant genetic dispersal events in modern times, spreading variants carried by European and African immigrants into distant parts of the world. The overwhelming majority of people on Earth have inherited a mix of variants tracing to major migration events such as these.