杏吧原创

ONE of the iconic scientific images of our age is the saw-tooth curve that shows how global temperatures have changed over the last half-million years. Based on Antarctic ice cores, it reveals troughs of cold and peaks of warmth that succeeded each other in an approximately 100,000-year cycle, as ice sheets at high latitudes grew and then collapsed again. It was during those periodic ice ages that the genus Homo evolved in Africa. When modern humans dispersed over the globe from around 200,000 years ago on, that marked the beginning of the end for other types of human.

Reading Before the Dawn is like travelling along that ice-core curve. It has it all: peaks of superb science writing, followed by dramatic collapse into spurious assertions that left me cold.

Science journalist Nicholas Wade discusses how human genetics is transforming our understanding of human history. These days, any archaeologist or historian who neglects the clues buried in the genetic variability of populations and individuals is simply not doing their job properly. My advice to anyone with ambitions to be an archaeologist or historian is therefore to study genetics as well as artefact typologies and royal successions. And if they won鈥檛 take my word for it, they should read Before the Dawn 鈥� but read it cautiously.

The author is a huge fan of human genetics, but he has a dismal view of archaeology. His opening gambit is how entirely hopeless that discipline is for understanding the past. According to Wade, 90 per cent of human history is irretrievably lost, and archaeology is powerless to say anything about ancestral human populations. So what, I wonder, have I been doing with my career? And what of those generations of archaeologists who have meticulously discovered and interpreted the evidence that has provided us with the human story from the days when we scavenged for meat on the African savannah?

If I felt chilly reading Wade鈥檚 opening statement, I was left shivering by his arguments about the inherent aggressiveness of humans, especially those who lived as nomadic hunter-gatherers. He is correct to say that there has been a reluctance on the part of archaeologists to address the extent of violence and warfare in human history, but there is simply neither the evidence nor the theory to support his claims that 鈥渆ven in the harshest possible environments, where it was a struggle enough to keep alive, primitive societies still pursued the more overriding goal of killing each other鈥�.

Wade鈥檚 view of the past is one of continual violence. He writes about the Neanderthals 鈥渃rushing鈥� the initial attempt of anatomically modern humans to penetrate the eastern Mediterranean region, and about the 鈥渃ollision of peoples鈥� when those in northern latitudes had to migrate south as the ice sheets expanded. There is neither archaeological, fossil nor genetic evidence for any of this, yet Wade argues that for millions of years, people were unable to live in settled societies because they were too aggressive. According to him, it required genetic changes for them to acquire more peaceful dispositions, which in turn allowed agriculture and settled life in villages.

鈥淲ade鈥檚 view of the past is one of continual violence鈥�

Much of this claim is based on an analogy with the aggressive Yanomami people of Brazil, even though they are settled horticulturalists. If one wishes to make gross simplifications, and I don鈥檛, it would be more accurate to say that the introduction of a sedentary lifestyle and farming removed the reliance on cooperation within and between communities that is central to hunter-gatherer lifestyles, and resulted in a vast increase in aggression and warfare.

This trough in Wade鈥檚 erudition is followed by a series of informative chapters on how recent studies of human genetic variation are relevant to understanding issues of racial variation, language evolution and recent history. In general my feelings about the book thawed in these chapters.

Wade provides a masterful summary of recent research, especially about the evolution of linguistic diversity, and a number of fascinating case histories such as the discovery of the secret life of Thomas Jefferson. I finished the book agreeing with him that we are entering a new age of historical research: one that is informed by, if not dominated by, human genetics.