Traditional discussions of how humanity became the dominant form of life, with a population of more than seven billion and counting, have focused on competition. Our ancestors seized land, so the story goes, wiped out other species—including our brethren the Neandertals—and hunted big predators to extinction. We conquered nature, red in tooth and claw.
Overall, however, this is an unlikely scenario. Our forebears were too small and vulnerable to rule the savanna. They must have lived in constant fear of pack-hunting hyenas, 10 different kinds of big cats and other dangerous animals. We probably owe our success as a species more to our cooperativeness than our capacity for violence.