We're not finished yet. Even today, scientists say that human beings are continuing to evolve as our genes respond to rapid changes in the world around us.

In fact, the pressures of modern life may be speeding up the pace of human evolution, some anthropologists think.

Their view contradicts the widespread 20th-century assumption that modern medical practice, antibiotics, better diet and other advances would protect people from the perils and stresses that drive evolutionary change.