In the BCE (Before the Common Era) days of the Roman Empire, Legionnaires tore across the land aboard horse-powered chariots. These were driven by charioteers, who commonly held the reins in their right hand while wielding a whip to make the horses go faster in their left.
It’s a generally recognized fact that about 90% of humans are right-handed, with a mere 10% being lefties. This oddity of genetics can be attributed to the fact that the brain’s left hemisphere controls the right side of the body, while the right hemisphere controls the left.
One theory suggests that during the evolutionary process of making stone tools, which were “invented” more than once throughout history, homo sapiens used their right hands more because the cognitive force that drives tool-making comes from the left half of the brain. Another hypothesis states that, thanks to our basic need to survive, we knew on some deeper level that competition and cooperation needed balance in order for the species to coexist and flourish. A common denominator between most divergent groups was that everyone was right-handed, and to promote the sharing of ideas and resources, everyone stayed that way. Curiously, most primates don’t favor one side over the other as much as humans.
Given all that, the charioteer holding the whip in his left hand led to chariots passing on the right side to avoid getting smacked. Therefore, the Romans are credited with inventing the European model of driving on the left side of the road.
