Anthropologist explores the dawn of human culture in new book

BY CHRISTIAN HEUSS

For millions of years human behavior and anatomy evolved hand in hand. But about 50,000 years ago human creativity and innovation exploded, while anatomical evolution stalled. The sudden appearance of novel tools, weapons and skillfully chiseled art objects indicate a radical change in human behavior. This process continues today. But what sparked this cultural leap remains one of the hottest debates in the modern anthropological sciences.

Richard Klein, professor of anthropological sciences, in his new book, The Dawn of Human Culture (John Wiley & Sons, April 2002), opens this absorbing discussion to a broader audience. Together with science writer Blake Edgar, Klein sifts through the key archeological clues and proposes a plausible theory for the latest stages of human evolution.

"Anthropology has more in common with a criminal trial than it does with a physics experiment," Klein says. It's a lineup of evidence and facts that allows researchers to arrive at a plausible conclusion.

In the 290-page book, Klein and Edgar present key archeological evidence in a light and accessible tone. Their book is illustrated by Klein and Kathryn Cruz-Uribe with maps and sketches of human fossils and art objects.

"The book is a general, nontechnical outline of human evolution," says Klein, who authored, among other books, the classic anthropology reference The Human Career.

Klein and Edgar start their evolutionary journey 5 million years back, when early humans still looked and behaved like apes. Only their upright two-legged gait pointed to an ongoing species separation from their chimpanzee ancestors. Over a period of 2.5 million years, these first humans grew taller and invented the first crude stone-flaking tools. More sophisticated tools, especially for hunting, and later the first hand axes transformed them into hunters who could complement their vegetarian diet with animal flesh and marrow.

Early humans migrated out of sub-Saharan Africa through what is now Egypt and Israel and spread throughout Europe and Asia. There, these early humans diverged into different subspecies of humans including the Neanderthals in Europe. For many hundreds of thousands of years, Neanderthals were the most advanced human species in Europe until a new wave of anatomically and behaviorally modern humans spread out from Africa and migrated to Europe and Asia.

This now widely accepted "Out-of-Africa-2" hypothesis is based on the appearance of anatomically and behaviorally modern humans on a small patch in Eastern Africa as recently as 50,000 years ago. All of a sudden these early modern humans developed a new repertoire of hunting skills, novel forms of social interaction and a sense of art. They became creative innovators expanding their mental and technical capabilities. These new achievements drove the early modern humans out of Africa to spread over Europe and Asia. Within a short period of only about 15,000 years they supplanted the Neanderthals in Europe and other nonmodern humans in other parts of the world.

The cause for the drastic change in behavior in the early modern humans is unknown. But the most plausible explanation for the success of modern humans is a sudden biological change. "A fortuitous mutation may have promoted the fully modern brain," Klein says. As human brains reached today's size hundreds of thousands of years earlier and skull size didn't change drastically, this mutation would have affected cognitive power rather than overall brain structure.

For Klein the neural mutation hypothesis is the most economical explanation of why anatomy and human behavior drifted apart. Fossilized skulls reveal little about the brain underneath. But a gene mutation may have changed critical neural processes such as speech and language.

Unfortunately, anthropology only demonstrates the radical nature and the consequences of the dawn of human culture. It says nothing about what prompted it, Klein says. Although the title of the book implies a focus on the last 50,000 years of evolution and Klein's mutation theory, it pushes the idea only tangentially. "It's a nontestable hypothesis," Klein admits. "The book is about human evolution as I understand the record. My genetic explanation for the major behavioral change 50,000 years ago is the most plausible one, but I can't prove it." SR