The human body is often visualized as a symmetrical form: Picture the geometric precision of Leonardo da Vinci’s iconic drawing of a man’s proportions encased by a circle and square. In reality, we are actually quite lopsided. Most people have a dominant ear; the same is true for eyes, feet, and hands. Handedness is perhaps the most obvious of these asymmetries.
From the time most children first start picking up and using objects, they tend to favor one hand over the other. And in a majority of humans, the right side is dominant: About 85 percent of the modern human population on Earth is right-handed.
Is this a trait that our hominin ancestors also possessed? How long has right-handedness outweighed left-handedness?
The evolutionary anthropologist Natalie Uomini was unaware that she would be tackling these questions when she began her academic career studying the origins of language. Her interest was in the so-called technological hypothesis, which suggests that the origin of hominin language lies in the teaching of stone toolmaking. Uomini started to investigate such tools to see what she might glean about the details of how exactly they were made.
Uomini focused on a collection of Acheulean tools—a technological toolkit that lasted for nearly 1.5 million years and was the primary tool type made by early Neanderthals and their predecessor, Homo heidelbergensis. Many of these tools are characterized as hand axes: multiuse, teardrop-shaped tools crafted from a core of flint, chert, or other similar stone.