During the evolution of the human species, right-handedness has been a predominant trait among individuals. Evidence from stone tools and teeth showed that right-handedness was a dominant trait in hominids. “The human-animal appears to be the only species exhibiting a genetically based preference for the use of one forelimb over another” (Toth 1985:607). In almost all other species, the split between a preferred limb was nearly fifty percent.

Stone tools can show archaeologists the history of a favored limb. Stone flakes were examined, and showed a heavy bias towards “right-oriented flakes” (Toth 1985:610). Archaeologists have inspected many stone flakes and found that when the stone flakes are “struck from a core, the flakes will exhibit areas of the cortex. When such flakes are oriented with their striking platforms upward and the dorsal surface towards the viewer, those with cortex on the right side suggest that the blow came from the right side” (Toth 1985:610). Archaeologist Nicholas Toth studied stone tools in Kenya, and Ambrona, Spain. His results yielded strong evidence of a right-handed preference. In Kenya, the ratio was 57:43 in favor of right-handedness. In Ambrona, the ratio was 61:39 in favor of right-handedness (Toth 1985:611). Since right-handedness is associated with the left hemisphere of the brain, there is an interesting debate on when the human brain developed in different human species and how right-handedness can show that.

Figure 1. Characteristics of flaking stone. Hammerstone hits the cobblestone and Point X and creates a flake scar.

Tools were not the only thing that pointed to a hand preference. Different striations of anterior teeth were studied by scientists. They wanted to see if the anterior teeth were affected by different eating tools. “19 specimens from Atupuerca/Ibeas, constitute the sample of anterior teeth of this Anteneandteral site showing buccal striations” (Bermudez de Castro and Jalvo 1988:404). The striations on these teeth were examined by the naked eye first and then inspected under the microscope. They found “similar orientation in all hominid teeth recovered from… different sites” (Bermudez de Castro and Jalvo 1988:409). Scientists then mirrored the neanderthals by making a mouth guard that fits the mouth. Porcelain teeth were then melted onto the mouth guard to mimic the striations. Then they cut off bite-sized pieces of meat with flint flakes. They found a series of striations that matched with their fossil anterior teeth. When looking at “the location of the striations, orientation; and microscopic features of the striations…the results indicate that they were produced with sharp flint by hominids who normally preferred to use their right hand” (Bermudez de Castro and Jalvo 1988:411).

Figure 2. Striation patterns of right and left-handed users. “A and C indicate a right-handed operator; B and D indicate a left-handed operator” (Bermudez de Castro and Jalvo 1988:410).

Right-handedness can be seen as a predominant trait throughout the history of hominids. Stone tools and teeth are examples of how hominids evolved. Their left hemispheres developed over time for the ability of hand preference to become relevant.