London: In a research, scientists have stated that an ancient human relative was "a primate equivalent of a cow who had huge teeth and liked to eat grass".

Scientists from University of Colorado Boulder say the hominid, known as Paranthropus boisei, ranged across the African landscape more than one million years ago and lived side-by-side with direct ancestors of humans.

Lead scientist Prof Matt Sponheimer said it was long assumed Paranthropus boisei ate nuts, seeds and hard fruit due to its powerful jaw muscles and the biggest and flattest molars of any known hominid in the anthropological record.

However, he said in recent years study of the wear marks of teeth from Nutcracker Man by other research teams has indicated it was likely eating items like fruit and grasses.

That evidence, combined with the latest study that measured the carbon isotopes embedded in fossil teeth to infer diet, indicates the rugged jaw and large, flat tooth structure may have been just the ticket for Nutcracker Man to mow down and swallow huge amounts of grasses or sedges at a single sitting, a daily newspaper reported.

Prof Sponheimer said, “Frankly, we didn't expect to find the primate equivalent of a cow dangling from a remote twig of our family tree. Fortunately for us, the work of several research groups over the last several years has begun to soften prevailing notions of early hominid diets.”

"If we had presented our new results at a scientific meeting 20 years ago, we would have been laughed out of the room,” Prof added.

For their study, the scientists removed tiny amounts of enamel from 22 Paranthropus boisei teeth collected in central and northern Kenya, each of which contained carbon isotopes absorbed from the types of food eaten during the lifetime of each individual.

In tropical environments, virtually all trees and bushes -- including fruits and leaves -- use the so-called C3 photosynthetic pathway to convert sunlight into energy, while savannah grasses use C4 photosynthetic pathway.

Prof Sponheimer said the isotope analysis indicated Nutcracker Men were much bigger fans of C4 grasses and sedges than C3 trees, shrubs and bushes.

The results indicated the collective diet of the 22 individuals averaged about 77 percent grasses and sedges for a period lasting at least 500,000 years.

The research team also compared the carbon isotope ratios of Paranthropus teeth with the teeth of other grazing mammals living at the same time and in the same area, including ancestral zebras, hippos, warthogs and pigs.

Paranthropus was part of a line of close human relatives known as australopithecines that are thought to have split into the genus Homo - which produced modern Homo sapiens - and the genus Paranthropus, that dead-ended.

(Agencies)