Paranthropus boisei - Ancient relative of humans dubbed Nutcracker Man may have preferred to eat grass


Ancient relative of humans dubbed Nutcracker Man may have preferred to eat grass

An ancient relative of humans dubbed 'Nutcracker Man' because of his powerful jaws and huge teeth may have actually preferred to eat grass, say scientists.

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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.

Anthropologist Professor Matt Sponheimer said it was long assumed Paranthropus boisei favoured nuts, seeds and hard fruit because of its huge jaws, powerful jaw muscles and the biggest and flattest molars of any known hominid in the anthropological record.

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

He said that evidence, combined with the new 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.

Prof Sponheimer, of the University of Colorado Boulder in the United States, 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."

For the new study, the researchers 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 and some sedges use the 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 per cent 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. The results indicated those mammals were eating primarily C4 grasses, virtually identical to Nutcracker Man.

Paranthropus was part of a line of close human relatives known as australopithecines that includes the famous three million-year-old Ethiopian fossil Lucy, seen by some as the matriarch of modern humans.

Roughly 2.5 million years ago, the australopithecines are thought to have split into the genus Homo - which produced modern Homo sapiens - and the genus Paranthropus, that dead-ended.

Prof Sponheimer added: "One key result is that this hominid had a diet fundamentally different from that of all living apes, and, by extension, favoured very different environments.

"And having a good idea of where these ancient creatures lived and what they ate helps us understand why some early hominids left descendants and others did not."

The first skull of an individual Nutcracker Man was discovered by co-author Meave Leakey's in-laws, Mary and Louis Leaky, in 1959 in Tanzania.

The study was published in the Proceedings of the National Academy of Sciences.