"I am become death, the destroyer of worlds." So said the physicist Robert Oppenheimer, who helped to invent the atomic bomb.

The two bombs dropped on Hiroshima and Nagasaki in 1945 killed around 200,000 Japanese people. No other species has ever wielded such power, and no species could.

The technology behind the atomic bomb only exists because of a cooperative hive mind: hundreds of scientists and engineers working together. The same unique intelligence and cooperation also underlies more positive advances, such as modern medicine.

But is that all that defines us? In recent years, many traits once believed to be uniquely human, from morality to culture, have been found in the animal kingdom (see part one in this two-part series). So, what exactly makes us special? The list might be smaller than it once was, but there are some traits of ours that no other creature on Earth can match.