Featured Research

from universities, journals, and other organizations

Tooth development and weaning in chimpanzees not as closely related as once thought

Date:
January 28, 2013
Source:
Harvard University
Summary:
Using a first-of-its-kind method, scientists have used digital photographs to show that, after the eruption of their first molar tooth, many juvenile chimps continue to nurse as much, if not more, than they had in the past. The research challenges earlier studies that linked juvenile chimps' tooth development with their weaning as a rough proxy for understanding similar developmental landmarks in the evolution of early humans.

For more than two decades, scientists have relied on studies that linked juvenile primate tooth development with their weaning as a rough proxy for understanding similar developmental landmarks in the evolution of early humans. New research from Harvard, however, is challenging those conclusions by showing that tooth development and weaning aren't as closely related as previously thought.
Credit: malexeum / Fotolia

For more than two decades, scientists have relied on studies that linked juvenile primate tooth development with their weaning as a rough proxy for understanding similar developmental landmarks in the evolution of early humans. New research from Harvard, however, is challenging those conclusions by showing that tooth development and weaning aren't as closely related as previously thought.

Related Articles


Using a first-of-its-kind method, a team of researchers led by professors Tanya Smith and Richard Wrangham and Postdoctoral Fellow Zarin Machanda of Harvard's Department of Human Evolutionary Biology used high-resolution digital photographs of chimps in the wild to show that after the eruption of their first molar tooth, many juvenile chimps continue to nurse as much, if not more, than they had in the past. Their study is described in a January 28 paper in the Proceedings of the National Academy of Sciences.

"When these earlier studies were published about 20 years ago, they found a very tight relationship between the eruption of the first molar and certain developmental milestones, particularly weaning," Smith explained. "A number of researchers have tried to extrapolate that relationship to the human fossil record, but it now appears that our closest living relative doesn't fit that pattern. That suggests we should be more cautious if we want to infer what juvenile hominins were like."

Getting an inside view of chimpanzee childhood, however, is no easy task.

Most prior studies of tooth development in juvenile chimps relied on two methods of collecting data -- observing captive animals or studying skeletal remains of wild primates. Both, however, also came with challenges for researchers.

Studies have shown that captive chimps grow dramatically faster -- often reaching adult size by age 10 or 11, compared to 13 to 15 for wild chimps. That early development means the milestones researchers rely on as proxies for understanding early human species likely occur earlier than they normally would. Researchers studying skeletal remains of wild primates face a similar challenge. To properly understand those developmental landmarks, remains must be properly identified and aged, a notoriously difficult process for primates in dense tropical forests.

To solve those problems, Smith, Wrangham and Machanda developed a unique method for studying juvenile chimps in the wild. Researchers studying the Kanyawara chimpanzee community in Kibale National Park in Uganda teamed up with wildlife photographers who snapped photos of juvenile chimp's teeth whenever they opened their mouths. The detailed photos, some of which captured the same individuals over months, allowed researchers to track precisely when molars erupted, and to correlate that information with chimp's behavior more closely than ever before.

What the images revealed, Smith and Machanda said, came as a surprise.

Where earlier studies suggested that juvenile primates were weaned shortly after their first molar erupts, their study showed that, in addition to eating more solid food, chimps continued to "suckle as much, if not more, than they had before," Smith said. "They were showing adult-like feeding patterns while continuing to suckle, which was unexpected."

While questions of why juvenile chimps continue to nurse -- in some cases for months -- have yet to be answered, Machanda said those questions will likely be the subject of future studies.

"We're now working on a project that's focused on body size and growth, but we're also planning future studies that will look at their energetic condition so we can understand what they're trying to get from the mother by continuing to nurse," she said. "What's interesting, however, is that there can be conflict surrounding this where the juveniles are trying to get as much as possible from the mother and the mother is actually covering up her nipples and moving around. Sometimes they'll even throw these temper tantrums that look exactly like human babies."

"I think there are two bottom lines here," Smith said. "One, I think, is a cautionary tale. The findings in this paper are going to challenge us to find other proxies for weaning and the spacing between offspring, but the other aspect that's exciting is that we have some suggestion that we should start looking at how feeding behaviors develop in the wild.

"No one has looked at how infants become more adult-like, both in their food choice and in the time they spend feeding," she continued. "This actually appears to correlate fairly well with dental development, so, while this is a preliminary finding, we may have a new anatomical proxy for when juvenile primates begin eating like adults."


Story Source:

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


Journal Reference:

  1. Tanya M. Smith, Zarin Machanda, Andrew B. Bernard, Ronan M. Donovan, Amanda M. Papakyrikos, Martin N. Muller, and Richard Wrangham. First molar eruption, weaning, and life history in living wild chimpanzees. PNAS, January 28, 2013 DOI: 10.1073/pnas.1218746110

Cite This Page:

Harvard University. "Tooth development and weaning in chimpanzees not as closely related as once thought." ScienceDaily. ScienceDaily, 28 January 2013. <www.sciencedaily.com/releases/2013/01/130128151926.htm>.
Harvard University. (2013, January 28). Tooth development and weaning in chimpanzees not as closely related as once thought. ScienceDaily. Retrieved December 21, 2014 from www.sciencedaily.com/releases/2013/01/130128151926.htm
Harvard University. "Tooth development and weaning in chimpanzees not as closely related as once thought." ScienceDaily. www.sciencedaily.com/releases/2013/01/130128151926.htm (accessed December 21, 2014).

Share This


More From ScienceDaily



More Plants & Animals News

Sunday, December 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Researchers Test Colombian Village With High Alzheimer's Rates

Researchers Test Colombian Village With High Alzheimer's Rates

AFP (Dec. 19, 2014) In Yarumal, a village in N. Colombia, Alzheimer's has ravaged a disproportionately large number of families. A genetic "curse" that may pave the way for research on how to treat the disease that claims a new victim every four seconds. Duration: 02:42 Video provided by AFP
Powered by NewsLook.com
Monarch Butterflies Descend Upon Mexican Forest During Annual Migration

Monarch Butterflies Descend Upon Mexican Forest During Annual Migration

Reuters - Light News Video Online (Dec. 19, 2014) Millions of monarch butterflies begin to descend onto Mexico as part of their annual migration south. Rough Cut (no reporter narration) Video provided by Reuters
Powered by NewsLook.com
The Best Protein-Filled Foods to Energize You for the New Year

The Best Protein-Filled Foods to Energize You for the New Year

Buzz60 (Dec. 19, 2014) The new year is coming and nothing will energize you more for 2015 than protein-filled foods. Fitness and nutrition expert John Basedow (@JohnBasedow) gives his favorite high protein foods that will help you build muscle, lose fat and have endless energy. Video provided by Buzz60
Powered by NewsLook.com
Birds Might Be Better Meteorologists Than Us

Birds Might Be Better Meteorologists Than Us

Newsy (Dec. 19, 2014) A new study suggests a certain type of bird was able to sense a tornado outbreak that moved through the U.S. a day before it hit. 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:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

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