Featured Research

from universities, journals, and other organizations

New Findings Challenge Conventional Ideas On Evolution Of Human Diet, Natural Selection

Date:
April 30, 2008
Source:
University of Arkansas
Summary:
New findings suggest that the ancient human "cousin" known as the "Nutcracker Man" wasn't regularly eating anything like nuts after all. Researchers used a combination of microscopy and fractal analysis to examine marks on the teeth of members of an ancient human ancestor species and found that what it actually ate does not correspond with the size and shape of its teeth. This finding suggests that structure alone is not enough to predict dietary preferences and that evolutionary adaptation for eating may have been based on scarcity rather than on an animal's regular diet.

Researchers examined the teeth of Paranthropus boisei, also called the "Nutcracker Man," an ancient hominin that lived between 2.3 and 1.2 million years ago. The "Nutcracker Man" had the biggest, flattest cheek teeth and the thickest enamel of any known human ancestor and was thought to have a regular diet of nuts and seeds or roots and tubers. But analysis of scratches on the teeth and other tooth wear reveal the pattern of eating for the "Nutcracker Man" was more consistent with modern-day fruit-eating animals.
Credit: Nicolle Rager Fuller, National Science Foundation

New findings suggest that the ancient human "cousin" known as the "Nutcracker Man" wasn't regularly eating anything like nuts after all.

A University of Arkansas professor and his colleagues used a combination of microscopy and fractal analysis to examine marks on the teeth of members of an ancient human ancestor species and found that what it actually ate does not correspond with the size and shape of its teeth. This finding suggests that structure alone is not enough to predict dietary preferences and that evolutionary adaptation for eating may have been based on scarcity rather than on an animal's regular diet.

"These findings totally run counter to what people have been saying for the last half a century," said Peter Ungar, professor of anthropology in the J. William Fulbright College of Arts and Sciences. "We have to sit back and re-evaluate what we once thought."

Ungar and his colleagues Frederick E. Grine of Cambridge University and Stony Brook University and Mark F. Teaford of Johns Hopkins University School of Medicine reported their findings in the PLoS One.

The researchers examined the teeth of Paranthropus boisei, an ancient hominin that lived between 2.3 million and 1.2 million years ago and is known popularly as the "Nutcracker Man" because it has the biggest, flattest cheek teeth and the thickest enamel of any known hominin. Since the first specimen was reported by Mary and Louis Leakey in 1959, scientists have believed that P. boisei fed on nuts and seeds or roots and tubers found on the savannas throughout eastern Africa because the teeth, cranium and mandible appear to be built for chewing and crunching hard objects.

"The morphology suggests what P. boisei could eat, but not necessarily what it did eat," Ungar said.

Anthropologists have traditionally inferred the diet of this and other ancient human ancestors by looking at the size and shape of the teeth and jaws. However, by looking at the patterns of microscopic wear on a tooth, scientists can get direct evidence for what these species actually ate.

Ungar and his colleagues used a combination of a scanning confocal microscope, engineering software and scale-sensitive fractal analysis to create a microwear texture analysis of the molars of seven specimens of P. boisei. The specimens spanned a time frame of almost a million years and were found in Kenya, Tanzania and Ethiopia. Using these techniques, they were able to create three-dimensional "point clouds" that showed the pits and scratches on the teeth.

The researchers looked at complexity and directionality of wear textures in the teeth they examined. Since food interacts with teeth, it leaves behind telltale signs that can be measured. Hard, brittle foods like nuts and seeds tend to lead to more complex tooth profiles, while tough foods like leaves lead to more parallel scratches, which corresponds with directionality.

They compared the dental microwear profiles of P. boisei to the microwear profiles of modern-day primates that eat different types of diets -- grey-cheeked mangabeys and brown capuchins, which eat mostly soft items but fall back on hard nuts or palm fronds, and the mantled howling monkey and silvered leaf monkey, which eat mostly leaves and other tough foods. They also compared the microwear analysis to analyses of teeth from some of the fossil's more contemporary counterparts -- Australopithecus africanus, which lived between 3.3 million and 2.3 million years ago, and Paranthropus robustus, which lived between 2 million and 1.5 million years ago.

The P. boisei teeth had light wear, suggesting that none of the individuals ate extremely hard or tough foods in the days leading up to death. It's a pattern more consistent with modern-day fruit-eating animals than with most modern-day primates.

"It looks more like they were eating Jell-o," Ungar said.

This finding, while contradictory to previous speculation on the diet of P. boisei, is in line with a paradox that has been documented in fish. Liem's Paradox states that animals may actively avoid eating the very foods they have developed adaptations for when they can find other food sources.

It appears that this paradox may hold true for P. boisei and for some modern-day primates as well.

"If you give a gorilla a choice of eating a sugary fruit or a leaf, it will take the fruit every time," Ungar said. "But if you look at a gorilla's skull, its sharp teeth are adapted to consuming tough leaves. They don't eat the leaves unless they have to."

This finding represents a fundamental shift in the way researchers look at the diets of these hominins.

"This challenges the fundamental assumptions of why such specializations occur in nature," Ungar said. "It shows that animals can develop an extreme degree of specialization without the specialized object becoming a preferred resource."

This project was funded in part by grants from the National Science Foundation.

Citation: Ungar PS, Grine FE, Teaford MF (2008) Dental Microwear and Diet of the Plio-Pleistocene Hominin Paranthropus boisei. PLoS One 3(4): e2044. doi:10.1371/journal.pone.0002044


Story Source:

The above story is based on materials provided by University of Arkansas. Note: Materials may be edited for content and length.


Cite This Page:

University of Arkansas. "New Findings Challenge Conventional Ideas On Evolution Of Human Diet, Natural Selection." ScienceDaily. ScienceDaily, 30 April 2008. <www.sciencedaily.com/releases/2008/04/080429204255.htm>.
University of Arkansas. (2008, April 30). New Findings Challenge Conventional Ideas On Evolution Of Human Diet, Natural Selection. ScienceDaily. Retrieved April 20, 2014 from www.sciencedaily.com/releases/2008/04/080429204255.htm
University of Arkansas. "New Findings Challenge Conventional Ideas On Evolution Of Human Diet, Natural Selection." ScienceDaily. www.sciencedaily.com/releases/2008/04/080429204255.htm (accessed April 20, 2014).

Share This



More Health & Medicine News

Sunday, April 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Nine-Month-Old Baby Can't Open His Mouth

Nine-Month-Old Baby Can't Open His Mouth

Newsy (Apr. 19, 2014) Nine-month-old Wyatt Scott was born with a rare disorder called congenital trismus, which prevents him from opening his mouth. Video provided by Newsy
Powered by NewsLook.com
'Holy Grail' Of Weight Loss? New Find Could Be It

'Holy Grail' Of Weight Loss? New Find Could Be It

Newsy (Apr. 18, 2014) In a potential breakthrough for future obesity treatments, scientists have used MRI scans to pinpoint brown fat in a living adult for the first time. Video provided by Newsy
Powered by NewsLook.com
Little Progress Made In Fighting Food Poisoning, CDC Says

Little Progress Made In Fighting Food Poisoning, CDC Says

Newsy (Apr. 18, 2014) A new report shows rates of two foodborne infections increased in the U.S. in recent years, while salmonella actually dropped 9 percent. Video provided by Newsy
Powered by NewsLook.com
Scientists Create Stem Cells From Adult Skin Cells

Scientists Create Stem Cells From Adult Skin Cells

Newsy (Apr. 17, 2014) The breakthrough could mean a cure for some serious diseases and even the possibility of human cloning, but it's all still a way off. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins