Unravelling Darwin’s ‘hunch’

Charles Darwin speculated that the origins of modern human beings may be traced to Africa. It took more than a century of hard research, exploration and scientific endeavour for his hunch to be vindicated.

Written in a gripping account that reads like a detective novel, Christa Kuljian provides a history of this validation of Darwin’s “hunch”. Kuljian is a writing fellow at the Wits Institute for Social and Economic Research. She took her first degree in the history of science at Harvard University, where prominent among her tutors was the world-renowned paleontologist, Stephen Jay Gould.

In addition to a master’s degree at Princeton, she has another from the University of the Witwatersrand in creative writing. Her superb academic training illuminates this book.

Kuljian deals insightfully with the interrelationship between politics and science, especially the science of paleontology. Politics and its kindred spirit, ideology, influenced not only the prevailing assumptions about human origins but also the ability of paleontologists to raise funds to enable them to undertake their research. Political support may result in direct grants from government, but also heightens general consciousness, facilitating generous donations from private foundations and other institutions.

Kuljian draws parallels and distinctions between Jan Smuts, statesman, all round academic and pre-apartheid prime minister, and post-apartheid president Thabo Mbeki. The intellectual curiosity of both was stimulated by the prospect that the origins of modern human beings may have begun in South Africa. Both thought that research in this regard would help to “put South Africa on the map”. Mbeki thought that it would give black South Africans a sense of self-pride. To this idea Smuts was impervious.

Under apartheid, the Nationalist government was indifferent, if not hostile, to the idea that “the cradle of humankind” may lie in South Africa. It was afraid of the effect science may have on the ideology of “difference” between and, correspondingly, the inherent “separateness” of races.

Apartheid prime minister and also an academic, Hendrik Verwoerd was afraid that science may implode his theory that, as the first white person came ashore at the Cape, the first black person crossed the Limpopo. In Verwoerdian ideology, South Africa, apart from a few politically irrelevant San and Khoi-Khoi, was a wilderness, awaiting possession by white people. Thus reasoned, there had been no colonial displacement of blacks.

Until fairly recent decades, racial prejudice in the great universities of the world impeded finding the location of the cradle. It was assumed that modern human beings must have originated in Europe or Asia. Raymond Dart, the “founding father” of paleontology in South Africa, was not unaffected by prejudicial thinking of a “racial hierarchy”.

Even Phillip Tobias, the internationally acclaimed paleontologist and an erstwhile doyen of South African liberalism, for a long time believed that there were different racial “types”, originating from a common ancestor who lived several millions of years ago.

The clinch came with the discovery, in the 1980s, from an analysis of mitochondrial DNA, which all human beings inherit from their mothers alone. The scientific deduction was that we all derive from a common maternal ancestor who lived some 200 000 years ago. This fact, together with the age-dating of fossil discoveries made in South Africa demonstrated, as conclusively as science is able to do, that the cradle of modern humanity was indeed in South Africa.

The implications were revolutionary. We are more closely related than science had hitherto imagined. Initially, Tobias was sceptical but once he accepted the scientific evidence, he came to the conclusion, professed publicly, that human beings were too closely related for it to make sense to talk of different human “races”.

“Mitochondrial Eve” was not the first woman to walk upon the earth. She would have had sisters and cousins and aunts, but their progeny died out. It is here that Kuljian is at her most brilliant. She grasps and explains well that evolution is not about mutation alone. It is genetic mutation, together with an ever-continuing process of reproductive “branching out” and dying out, that is at the core of the explanation for evolution.

Disappointingly, Kuljian does not deal with another genetic discovery that was no less significant. The rate of mutation of the Y-chromosome indicates that we all share a common male ancestor who lived about 60 000 years ago — perhaps even more recently. This, too, has revolutionary implications that extend beyond the knowledge of our close relatedness. It means that the first human migrations out of Africa could not have begun before he lived and that hominid remains found elsewhere in the world, dating from before then, could not be those of ancestors but of branches of human-like creatures that died out.

The explanation for the counter-intuitive fact that “Mitochondrial Eve” did not meet “Y-chromosome Adam” is that he would have had brothers and cousins and uncles whose male offspring died out. To an extent greater than females, mammalian males tend to reproduce either a lot or not at all. This explains not only why male lines of descent tend to die out more so than female ones but also why the ratio between the proportion of females to males remains more or less constant and equal.

The science behind this lies partly in the inherent fragility of the Y-chromosome, it being inherited in a straight line from father to son. The same permutations for recombination as the XX female chromosomes have, are therefore not possible. Recombination acts to mitigate genetic weakness.

Additionally, power, conquest and plunder made possible the abundant “sowing of the seed” by those males who were dominant. One in six males in Mongolia is a direct descendant of Genghis Khan.

Darwin’s Hunch contributes to a larger South African debate: What are we to make of “race”? It is scientifically irrelevant but is a “social construct”. How do we straddle the paradox? To make progress the truth of our shared humanity will matter. The solid foundation is that science has shown that there are no innate racial hierarchies.

The book is not without its humorous episodes. Kuljian records that persons prominent in public life in South Africa today have exclaimed or used expressions like: “No one is going to tell me that I am descended from a baboon!” No scientist ever has. We and monkeys and baboons descend from a common ape-like ancestor that lived many millions of years ago. That ancestor no longer exists. Monkeys and baboons are neither our brothers and sisters nor our ancestors, but are our evolutionary cousins.

Tobias had no interest in women as partners in romantic liaisons. When a fellow scientist signed off a letter to him “with love”, the curt formality of his response would have dispelled any illusions she may have had in this regard.

Kuljian paints the portraits of her heroes “warts and all”. For example, she recounts how Tobias let his personal preference cloud his judgment as to who should be appointed as his academic successor.

Beautifully and entertainingly written, Darwin’s Hunch adds pithiness to the aphorism that “truth is stranger than fiction”. The book is a literary dance with science.

Nigel Willis is a judge of the Supreme Court of Appeal. He writes in his personal capacity.

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