Nine out of 10 people are right-handed, but most animals don't seem to have a preference for using one hand (or paw) over the other when manipulating objects and doing tasks. Exactly how handedness came about remains a mystery, but new research claims to have dated this tendency in the dawn of human evolution, and it wasn't during the time of the Homo sapiens.
A Homo habilis who lived in the current region of Tanzania approximately 1.8 million years ago seems to have been right-handed, according to a new study.
The paper, published Oct. 20 in the Journal of Human Evolution, dismisses the previous findings that suggested the earliest right-handed specimen to have walked the earth was a Neanderthal, who lived approximately 430,000 years ago.
"This is an exciting paper because it strongly suggests right-handed tool use in early Homo around 1.8 million years ago," noted Debra Guatelli-Steinberg, an anthropologist at the Ohio State University, who was not part of the research.
By analyzing bones and the structures of their remains, scientists were able to gather evidence of handedness in early humans.
David Frayer, a paleoanthropologist and professor emeritus at the University of Kansas, observed abnormal scratches on the teeth of an H. habilis fossil approximately a decade ago. Most of these seem to have been done by a scratch from left to right, as if an object was dragged down across the teeth from the right side.
A closer investigation suggested that the marks were similar to the ones on mouth guards in experiments where people used their teeth while cutting meat or another strong material.
There is a scenario that comes along with this hypothesis: the early human supposedly used a tool to cut tough meat into smaller pieces that could be easily eaten. The human used his or her teeth to hold the meat and the left hand to pull it away. Then, with the right hand, a sharp tool was used to cut the meat near the mouth. When the hand slipped, the tool would then have scraped across the front teeth to create the marks.
A total of 559 striation were identified on the frontal teeth, with less than 50 percent of the marks being right striations (46.5 percent, accounting for 260 from the 559 striations), according to the study.
"While [this] specimen indicates right-handed tool use, we will need larger samples from early Homo to assess the frequency of handedness in these hominins - that is the more interesting question from the standpoint of understanding how far back the modern human predilection for right-hand use can be pushed back into time," agreed Guatelli-Steinberg.
