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Did our mammalian ancestors eat only vegetables, avoiding eggs and milk, or did
they hunger for meat as well? It’s hard for anthropologists to determine the
diet of early mammals because fossil analysis provides too little information.
But a new method that measures the size of chips in tooth fossils can help
determine the kinds of foods early humans consumed.
Prof. Herzl Chai of
Tel Aviv University’s School of Mechanical Engineering – in collaboration with
scientists from George Washington University (GWU) and the US National Institute
of Standards and Technology (NIST) – has developed an equation for determining
how the size of a chip found in tooth enamel relates to the bite force needed to
produce the chip.
With the aid of this information, researchers can
better determine the type of food that early humans consumed.
the only relevant fossils preserved over many thousands of years, Chai explains.
Made of hard, mineralized material, enamel teeth remain relatively intact. Teeth
that display a greater number of large chips indicate that animals like our
early ancestors were consuming harder foods such as nuts, seeds or meat with
bones. A lesser amount of small chips demonstrates that the diet more likely
consisted of softer foods such as vegetables. Chai’s findings were recently
reported in Biology Letters.
In his study, Chai combined his mechanical
engineering background with the expertise of GWU anthropologists and NIST
material scientists to develop a simple equation predicting the maximum bite
force used to create a tooth chip. The equation correlates well with a
commonly-used equation from jaw mechanics – a more complex approach for
determining the maximum bite force an animal can deliver.
fracture mechanics, which involves the formation of cracks in brittle materials,
Chai’s equation takes into account the dimensions of the chip and its distance
from the edge of the tooth – and from there solves for the bite force needed.
The maximum force an animal can apply, he writes, relates to the thickness of
the enamel and the size of the tooth itself.
“The bigger the tooth, the
bigger the area for chips to develop, and therefore, the more force the animal
can produce,” he says. The team surveyed tooth fossils from many types of
mammals, including six hominins, gorillas and chimpanzees.
A tooth chip
is a permanent signature of consumption, says maintains Chai. His method
demonstrates that the probable food sources of a given animal can be determined
from a small number of wellpreserved teeth. The fossils used for this particular
study were widely available at museums. This is an improvement over previous
methods, which relied solely on jaw mechanics and required an almost complete
skull to determine eating habits.
This moves researchers one step closer
to grasping the dietary habits of early mammals. Although the study of tooth
chips cannot, thus far, reveal exactly what food produced the chip, it allows
researchers to determine a range of foods, providing valuable information about
the animal’s life.LEONARDO’S MODEL FLIES
Mankind since Leonardo da Vinci
has long wanted to imitate the birds and fly with wings; fixed-winged aircraft
are just not the same. Now engineers at the University of Toronto have built and
successfully flown a “human-powered ornithopter” called Snowbird. UPI recently
reported that the craft, with flapping wings, looks similar to the da Vinci
design sketched in 1485.
It made history by being the first craft of its
kind to stay aloft, and its success was confirmed by observers from the
Federation Aeronautique Internationale, the world-governing body for air sports
and aeronautical world records.
Todd Reichert, an engineering doctoral
candidate at the university’s institute for aerospace studies, headed the team
that built the Snowbird, which remained aloft for 19.3 seconds and covered a
distance of 158 meters at an average speed of 25.7 kilometers per hour.
“Throughout history, countless men and women have dreamt of flying like a bird
under their own power, and hundreds, if not thousands have attempted to achieve
it,” said an enthused Reichert, who lost nine kilos to fly the craft. “This
represents one of the last of the aviation firsts.”
The plane has a wing
span of 35 meters (like a Boeing 737), but weighs less than the pillows on an
airliner – just 42 kilos.