Humans are the only primate to demonstrate handedness at the
species level and Anthropology professor Richard Lazenby believes that
understanding this phenomenon will lead to new answers concerning our
evolution.
About 90% of people are right-handed, but nobody really
knows why. We also don’t know when we developed a hand preference. Was it a few
thousand years ago or a few million? Answering the question goes far beyond simply
understanding hand preference. It may go to the core of human evolution and our
development of a sophisticated language. This is possible because fine motor
control and speech function have both gradually evolved in the left side of the
brain. “Handedness may be tied both to the development of fine manipulation for
tool production and to speech for the transmission of knowledge related to such
activities,” says Dr. Lazenby. “If this is an area where humans are different
from other primates, it begs a question: When in our evolutionary history did
our ancestors develop a right-hand bias?”
Thanks to funding from the Natural Sciences and Engineering
Research Council of Canada, Dr. Lazenby is answering the question together with
colleagues from the University of Calgary and the Caribbean Primate Research Centre at
the University of
Puerto Rico. Just as
exercising muscles makes them grow larger, bone size and shape are also determined
by their mechanical functions. Using 200-year old skeletons from an
archaeological dig in Ontario,
the research team is comparing the hand structures on the left and right sides.
State-of-the-art computing equipment is making it possible. Very high-resolution
images of both the outside and inside of the bone are providing information on
overall size, the density of the bone, and the internal microarchitecture.
“The equipment has helped us identify a pattern,” says Dr.
Lazenby. “Among some of our findings, we are seeing that the right-hand bones
are larger and there is a greater volume of bone per unit of mass.”
Tying their results to evolution, Dr. Lazenby and his fellow
researchers will extend the same techniques to studying the bone structures of
non-human primates that don’t prefer one hand over the other. Eventually, their
findings will be applied to the human fossil record in an attempt to answer Dr.
Lazenby’s initial question: When did our ancestors develop a right-hand bias
and what does it mean?
Contact the Office of Communications
Rob van Adrichem
Director, Media & Public Relations
