Contemplating the clock within

SINCE the invention of agricultural civilisations about 10,000 years ago, we humans have been inordinately proud of our varied "culture" and consider ourselves superior to all other creatures on earth. Ironically, at the same time, we try to dominate each other culturally through aggression all the time, a mission to which the best of our ingenuity and resources are devoted. Most such socio-cultural strife is rooted in notions of "biological superiority" of one human group over another. The Journey of Man: A Genetic Odyssey is a good antidote to such notions. Author Spencer Wells shows that human populations all over the world are pretty much alike in their genetic make up.

Using an illustrative metaphor, the author says that each human being alive on earth today is a "family recipe" of genes passed down through generations. Every one of us is an admixture resulting from the great genetic churning that followed the emergence of Homo sapiens (modern humans) out of Africa about 60,000 years ago. Any single human population, anywhere in the world today, is a cocktail that captures more than 85 per cent of all extant human genetic diversity.

Earlier scientific reconstructions of human origins depended on studies of old bones and cultural artefacts, trying to link them to geological, climatic and ecological changes to anchor events in time and space. With the emergence of the powerful new research tools based on modern molecular genetics, scientists can now track human evolution even more accurately. Genetic samples drawn from human populations in different parts of the world enable scientists to trace their lineages back all the way through an African origin and subsequent colonisation of remaining continents. Ironically, however, soon after scientists have gained this remarkable ability to read molecular clocks set within us, the window of opportunity to do so appears to be closing forever. Reason: the unprecedented rapidity with which the hitherto relatively sedentary human populations are inter-mixing across the globe.

In this scientific tour de force, geneticist Wells describes the rise of early hominids in Africa as an evolutionary consequence of global climate change, expansion of grasslands, and the consequent adaptive transformation of ape-like Ardiopithecenes into roaming bands of man-apes that stood erect and hunted cooperatively, thereby developing greater intellectual capacity. Originating from their African cradle nearly two million years ago, early hominids such as the Homo erectus soon spread all the way to Indonesia ("the Java man") and China ("the Peking man"). A later offshoot, the Neanderthals, reached Europe. However, these Homo lineages ultimately lost the evolutionary struggle manifested through environmental changes and competition with other creatures. They left no survivors on earth.

All modern humans trace their direct ancestry to hominids called Australopithcenes that inhabited Africa over 2 million years ago. Current DNA-based techniques can trace the lineage of Homo sapiens back 200,000 years ago to Africa. Although Wells marshals evidence from diverse fields of enquiry to his task of tracing human origins, he primarily writes about a stunning new array of genetic explorations in the last two decades. By tracking a genetic marker called M-168 that is present in the Y-chromosomes of men, Wells demonstrate how the first bands of modern humans, perhaps not unlike present-day African "bushmen", moved out of Africa and colonised the Arabian peninsula about 60,000 years ago. Almost immediately, a sub-group bearing the genetic marker M-130 rapidly moved along the resource-rich coastal fringe of southern Asia, populating Southeast Asia and Australia within a few thousand years. Because of lower sea level that prevailed, the Asian coastline was aligned very differently with far greater connectivity among landmasses, facilitating the rapid migration of M-130 lineage. These people were ancestors to the aboriginal human groups of Australia as well as in south and south-eastern Asia.

Another branch off the M-168 colonisers that bore the genetic marker M-89 moved into middle-east (45,000 years ago) and gave rise to lineage M-9 that moved into southern part of central Asia (40,000 years ago), following teeming herds of game in those vast grasslands. The M-9 lineage subsequently forked out in three directions: M-45 penetrated deeper into central Asia 35,000 years ago; M-175 moved into the Tibet-southern China region 30,000 years ago and a population bearing the genetic marker M-20 moved into the Indian subcontinent. This M-20 lineage intermixed with the earlier coastal migrant populations of M-130. Based on genetic evidence, Wells suggests the encounter between these groups may have been brutal and one-sided, with most men of the M-130 lineage being eliminated and their women being interbred with the more "advanced" (read aggressive) M-20 lineage. Thus, clearly all modern south Asians are a "genetic cocktail" of at least 30,000-year vintage, not withstanding notions of "superiority by birth" promoted by assorted swamis, acharyas, jagadgurus, and mullahs who proliferate in India, Sri Lanka, Pakistan and Bangladesh now. The biological evidence shows that their culturally inspired notions of "different blood" coursing through the veins of Hindus, Buddhists, Muslims, Dalits or whoever else, are absurd.

This human odyssey continued across the earth. The bearers of the marker M-242, descendants of M-45, advanced across the frozen north Asian continent, adapting to ice-age conditions to hunt woolly mammoths. They colonised the "new world" 20,000 years before Christopher Columbus "discovered" it. Within a few thousand years, these original Americans had spread all the way to the tip of South America. Around the same time, racing across China was a group of people bearing the marker M-122, descendants of M-175, who eventually populated much of Southeast Asia.

About 10,000 years ago, as ice-sheets retreated across Europe and Northern Asia, modern humans bearing genetic marker M-172 moved into Europe. The warm-moist climatic regime that we now live in emerged. The earth was already peopled, and ready for the next human revolution: discovery of agriculture and the consequent ability to modify the environment itself, unlike any other creature before.

Wells synthesises the genetic evidence with current research in geology, palaeontology, archaeology, anthropology and linguistics to make a robust case for his account of the human journey. A Harvard-trained expert on human evolution, Wells peppers his narrative with stories of major scientific breakthroughs along the way, ranging from insights of pioneers like Charles Darwin and Paul Broca to findings of modern-day scientists like Luigi Calvelli-Sforza, Richard Lewontin, Rebecca Caan and others. The book is nicely illustrated with a series of line drawings and range maps. Photographer Mark Reads' remarkable portfolio of human-cultures significantly enriches the text, although the numerically abundant and highly varied southern Asian cultures appear to be under-represented in it.

The Journey of Man explains how a single species came to dominate the earth so quickly (in evolutionary terms) through a series of steps: a vegetarian forest-edge ape that adapted to grassland habitats by standing upright — in the process, becoming a social carnivore capable of communicating complex thoughts — thus launching on an odyssey that peopled the entire planet in a mere 2000 generations. It provides a solid underpinning of evolutionary biology for those who want to explore ecology, anthropology and social evolution anywhere on earth.

The book also offers a sobering fact: every human alive on earth today is descended from a single flesh-and-blood man who stalked antelopes on the African plains about 60,000 years ago. This fact carries an important lesson for our strife-torn world: the urgent need to pull our political discourse back to the path of reason. And, thereby, to rescue our culture from the clutches of stealth-bombing crusaders, trishul-wielding sadhus, crazed terrorists and other self-proclaimed messiahs who are spilling blood. Blood that bears the same M-168 genetic marker all of us inherited from our single confirmed ancestor.

The Journey of Man: A Genetic Odyssey, Spencer Wells, Princeton University Press, 2003, p. 256.

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