Christopher Henshilwood

Archaeologists in South Africa have recently unearthed some of the earliest evidence of human behavior - a cache of ostrich eggs dating back 60,000 years, etched with intricate geometric designs. 

The abstract carvings are signs of what archaeologists call 'symbolic thinking,' a capacity particular to Homo sapiens. Unlike earlier hominids, our brains allow us to affix meaning to objects, to draw associations, to recognize and create symbols.  Symbolic thinking is the roots of writing, language and art; it is, to risk grandiosity, what makes us human. 

So when the team at Diepkloof Rock Shelter, led by prehistorian Pierre-Jean Texier, dug up the 60,000-year-old decorated ostrich eggs, they knew they'd found something special. The eggs suggest that we 'became human' - i.e. started creating art, decorating objects and thinking symbolically - 20,000 earlier than scholars had originally thought.