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.

Teeth are 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.

Drawn from 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.

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