Featured Research

from universities, journals, and other organizations

Big Brains Arose Twice In Higher Primates

Date:
July 9, 2008
Source:
American Museum of Natural History
Summary:
After taking a fresh look at an old fossil, researchers determined that the brains of the ancestors of modern neotropical primates were as small as those of their early fossil simian counterparts in the Old World. This means one of the hallmarks of primate biology, increased brain size, arose independently in isolated groups -- the platyrrhines of the Americas and the catarrhines of Africa and Eurasia.

Fossil Chilecebus from South America.
Credit: John Weinstein, The Field Museum

After taking a fresh look at an old fossil, John Flynn, Frick Curator of Paleontology at the American Museum of Natural History, and colleagues determined that the brains of the ancestors of modern Neotropical primates were as small as those of their early fossil simian counterparts in the Old World. This means one of the hallmarks of primate biology, increased brain size, arose independently in isolated groups--the platyrrhines of the Americas and the catarrhines of Africa and Eurasia.

"Primatologists have long suspected that increased encephalization may have arisen at different points in the primate evolutionary tree, but this is the first clear demonstration of independent brain size increase in New and Old World anthropoids," says Flynn of the paper that appeared in the Museum's publication Novitates this June. Encephalization is the increase in brain size relative to body size. Animals with large encephalization quotients (E.Q.'s) are those with bigger brains relative to their body size in comparison to the average for an entire group. Most primates and dolphins have high E.Q.'s relative to other mammals, although some primates (especially apes and humans) have higher E.Q.'s than others.

At the heart of the new paper is the development of more accurate equations for estimating body size in platyrrhines, or New World "monkeys." Most fossils are fragments of skulls or teeth so, to help in estimating their body size (and then E.Q.), Flynn and colleagues collected 80 measurements of the skulls, jaws, and teeth of 17 different species of living New World monkeys that ranged across the full spectrum of body sizes. This study is one of the first to estimate body size with platyrrhines instead of their better-studied counterparts from the Old World, and this detailed analysis uses new statistical approaches to tease out which characteristics correlate best with body size. The goal is to apply this equation to fossilized specimens.

Chilecebus, found high in the Andes and described by Flynn and collaborators in 1995 in Nature, is one such fossil. The skull dates to 20 million years ago and is the oldest and most complete well-dated primate skull from the New World. In the Novitates paper, Flynn and colleagues more accurately estimate that Chilecebus weighed about 583 grams and had an E.Q. of only 1.11--a much smaller relative brain size than any living New or Old World anthropoid, which have E.Q.'s ranging from 1.39-2.44 (and even higher for humans).

"The result is clear: early fossil members of both the New World and Old World anthropoid lineages had small brain sizes, thus the larger brain sizes seen in both groups today must have arisen independently," says Flynn. "Documenting that large brains evolved separately several times within Primates will enhance understanding of the timing and pathways of brain expansion and its effects on skull growth and shape, and may lead to new insights into the genetic controls on encephalization."

Eric Delson, the Chair of Anthropology at Lehman College, City University of New York and a Research Associate at the Museum, concurs. "This work confirms that brain size increase may be one of the common characteristics of all primates," he says. "The relatively small brain of Chilecebus contrasts with that of the slightly younger (16.5 million years ago), larger brained fossil Killikaike found in Argentina and described two years ago. It is probable that brain size also increased independently in the lemurs of Madagascar, as well as in the apes (of which humans are the extreme case) and the cercopithecid monkeys of Africa and Asia."

Other researchers on the study include lead author Karen E. Sears of the Department of Animal Biology at The University of Illinois at Urbana-Champaign, John A. Finarelli of the Department of Geological Sciences at the University of Michigan, and Andre R. Wyss of the Department of Geological Sciences at the University of California at Santa Barbara. This research was supported by the National Science Foundation, the John S. Guggenheim Memorial Foundation, and fellowships from The Field Museum, the University of Chicago and the University of Michigan.


Story Source:

The above story is based on materials provided by American Museum of Natural History. Note: Materials may be edited for content and length.


Cite This Page:

American Museum of Natural History. "Big Brains Arose Twice In Higher Primates." ScienceDaily. ScienceDaily, 9 July 2008. <www.sciencedaily.com/releases/2008/07/080709110839.htm>.
American Museum of Natural History. (2008, July 9). Big Brains Arose Twice In Higher Primates. ScienceDaily. Retrieved September 20, 2014 from www.sciencedaily.com/releases/2008/07/080709110839.htm
American Museum of Natural History. "Big Brains Arose Twice In Higher Primates." ScienceDaily. www.sciencedaily.com/releases/2008/07/080709110839.htm (accessed September 20, 2014).

Share This



More Plants & Animals News

Saturday, September 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: San Diego Zoo Welcomes Cheetah Cubs

Raw: San Diego Zoo Welcomes Cheetah Cubs

AP (Sep. 20, 2014) The San Diego Zoo has welcomed two Cheetah cubs to its Safari Park. The nearly three-week-old female cubs are being hand fed and are receiving around the clock care. (Sept. 20) Video provided by AP
Powered by NewsLook.com
Chocolate Museum Opens in Brussels

Chocolate Museum Opens in Brussels

AFP (Sep. 19, 2014) Considered a "national heritage" in Belgium, chocolate now has a new museum in Brussels. In a former chocolate factory, visitors to the permanent exhibition spaces, workshops and tastings can discover derivatives of the cocoa bean. Duration: 01:00 Video provided by AFP
Powered by NewsLook.com
Could Grief Affect The Immune Systems Of Senior Citizens?

Could Grief Affect The Immune Systems Of Senior Citizens?

Newsy (Sep. 19, 2014) The study found elderly people are much more likely to become susceptible to infection than younger adults going though a similar situation. Video provided by Newsy
Powered by NewsLook.com
Jury Delivers Verdict in Salmonella Trial

Jury Delivers Verdict in Salmonella Trial

AP (Sep. 19, 2014) A federal jury has convicted three people in connection with an outbreak of salmonella poisoning five years ago that sickened hundreds of people and was linked to a number of deaths. (Sept. 19) Video provided by AP
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