Featured Research

from universities, journals, and other organizations

The Secret To Chimp Strength

Date:
April 8, 2009
Source:
University of Chicago Press Journals
Summary:
An evolutionary biologist argues that humans may lack the strength of chimps because our nervous systems exert more control over our muscles. Our fine motor control prevents great feats of strength, but allows us to perform delicate and uniquely human tasks.

Research suggests that humans may lack the strength of chimps because our nervous systems exert more control over our muscles.
Credit: iStockphoto/Jeryl Tan

February's brutal chimpanzee attack, during which a pet chimp inflicted devastating injuries on a Connecticut woman, was a stark reminder that chimps are much stronger than humans—as much as four-times stronger, some researchers believe. But what is it that makes our closest primate cousins so much stronger than we are? One possible explanation is that great apes simply have more powerful muscles.

Indeed, biologists have uncovered differences in muscle architecture between chimpanzees and humans. But evolutionary biologist Alan Walker, a professor at Penn State University, thinks muscles may only be part of the story.

In an article published in the April issue of Current Anthropology, Walker argues that humans may lack the strength of chimps because our nervous systems exert more control over our muscles. Our fine motor control prevents great feats of strength, but allows us to perform delicate and uniquely human tasks.

Walker's hypothesis stems partly from a finding by primatologist Ann MacLarnon. MacLarnon showed that, relative to body mass, chimps have much less grey matter in their spinal cords than humans have. Spinal grey matter contains large numbers of motor neurons—nerves cells that connect to muscle fibers and regulate muscle movement.

More grey matter in humans means more motor neurons, Walker proposes. And having more motor neurons means more muscle control.

Our surplus motor neurons allow us to engage smaller portions of our muscles at any given time. We can engage just a few muscle fibers for delicate tasks like threading a needle, and progressively more for tasks that require more force. Conversely, since chimps have fewer motor neurons, each neuron triggers a higher number of muscle fibers. So using a muscle becomes more of an all-or-nothing proposition for chimps. As a result, chimps often end up using more muscle than they need.

"[A]nd that is the reason apes seem so strong relative to humans," Walker writes.

Our finely-tuned motor system makes a wide variety of human tasks possible. Without it we couldn't manipulate small objects, make complex tools or throw accurately. And because we can conserve energy by using muscle gradually, we have more physical endurance—making us great distance runners.

Great apes, with their all-or-nothing muscle usage, are explosive sprinters, climbers and fighters, but not nearly as good at complex motor tasks. In other words, chimps make lousy guests in china shops.

In addition to fine motor control, Walker suspects that humans also may have a neural limit to how much muscle we use at one time. Only under very rare circumstances are these limits bypassed—as in the anecdotal reports of people able to lift cars to free trapped crash victims.

"Add to this the effect of severe electric shock, where people are often thrown violently by their own extreme muscle contraction, and it is clear that we do not contract all our muscle fibers at once," Walker writes. "So there might be a degree of cerebral inhibition in people that prevents them from damaging their muscular system that is not present, or not present to the same degree, in great apes."

Walker says that testing his hypothesis that humans have more motor neurons would be fairly straightforward. However, he concedes that testing whether humans have increased muscle inhibition could be a bit more problematic.


Story Source:

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


Journal Reference:

  1. Alan Walker. The Strength of Great Apes and the Speed of Humans. Current Anthropology, 2009; 50 (2): 229 DOI: 10.1086/592023

Cite This Page:

University of Chicago Press Journals. "The Secret To Chimp Strength." ScienceDaily. ScienceDaily, 8 April 2009. <www.sciencedaily.com/releases/2009/03/090330200829.htm>.
University of Chicago Press Journals. (2009, April 8). The Secret To Chimp Strength. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2009/03/090330200829.htm
University of Chicago Press Journals. "The Secret To Chimp Strength." ScienceDaily. www.sciencedaily.com/releases/2009/03/090330200829.htm (accessed July 28, 2014).

Share This




More Plants & Animals News

Monday, July 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Deadly Ebola Virus Threatens West Africa

Deadly Ebola Virus Threatens West Africa

AP (July 28, 2014) West African nations and international health organizations are working to contain the largest Ebola outbreak in history. It's one of the deadliest diseases known to man, but the CDC says it's unlikely to spread in the U.S. (July 28) Video provided by AP
Powered by NewsLook.com
Traditional African Dishes Teach Healthy Eating

Traditional African Dishes Teach Healthy Eating

AP (July 28, 2014) Classes are being offered nationwide to encourage African Americans to learn about cooking fresh foods based on traditional African cuisine. The program is trying to combat obesity, heart disease and other ailments often linked to diet. (July 28) Video provided by AP
Powered by NewsLook.com
Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Newsy (July 28, 2014) The asteroid that killed the dinosaurs struck at the worst time for them. A new study says that if it hit earlier or later, they might've survived. Video provided by Newsy
Powered by NewsLook.com
Raw: Sea Turtle Hatchlings Emerge from Nest

Raw: Sea Turtle Hatchlings Emerge from Nest

AP (July 27, 2014) A live-streaming webcam catches loggerhead sea turtle hatchlings emerging from a nest in the Florida Keys. (July 27) 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