Featured Research

from universities, journals, and other organizations

What evolved first, a dexterous hand or an agile foot?

Date:
October 6, 2013
Source:
RIKEN
Summary:
Resolving a long-standing mystery in human evolution, new research indicates that early hominids developed finger dexterity and tool use ability before the development of bipedal locomotion.

Shape of the hand and foot in two primate species. The fingers are represented independently (colour coded) in the primate somatosensory cortex (SI). By contrast, the representations of the toes are fused, with the exception of the big toe in humans.
Credit: Image courtesy of RIKEN

Resolving a long-standing mystery in human evolution, new research from the RIKEN Brain Science Institute indicates that early hominids developed finger dexterity and tool use ability before the development of bipedal locomotion.

Combining monkey and human behavior, brain imaging, and fossil evidence, a research team led by neurobiologist Dr. Atsushi Iriki and including Dr. Gen Suwa, an anthropologist from the University of Tokyo Museum, have overturned the common assumption that manual dexterity evolved after the development of bipedal locomotion freed hominid hands to use fingers for tool manipulation.

In a study published today in Philosophical Transactions of the Royal Society, the researchers employed functional magnetic resonance imaging in humans and electrical recording from monkeys to locate the brain areas responsible for touch awareness in individual fingers and toes, called somatotopic maps. With these maps, the researchers confirmed previous studies showing that single digits in the hand and foot have discrete neural locations in both humans and monkeys.

However, the researchers found new evidence that monkey toes are combined into a single map, while human toes are also fused into a single map, but with the prominent exception of the big toe, which has its own map not seen in monkeys. These findings suggest that early hominids evolved dexterous fingers when they were still quadrupeds. Manual dexterity was not further expanded in monkeys, but humans gained fine finger control and a big toe to aid bipedal locomotion.

"In early quadruped hominids, finger control and tool use were feasible, while an independent adaptation involving the use of the big toe for functions like balance and walking occurred with bipedality," the authors explained.

The brain study was supported by analysis of the well-preserved hand and feet bones of a 4.4 million year-old skeleton of the quadruped hominid Ardipithecus ramidus, a species with hand dexterity that preceded the human-monkey lineage split.

The findings suggest that the parallel evolution of two-legged locomotion and manual dexterity in hands and fingers in the human lineage were a consequence of adaptive pressures on ancestral quadrupeds for balance control by foot digits while retaining the critical capability for fine finger specialization.

"Evolution is not usually thought of as being accessible to study in the laboratory," stated Dr. Iriki, "but our new method of using comparative brain physiology to decipher ancestral traces of adaptation may allow us to re-examine Darwin's theories."


Story Source:

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


Journal Reference:

  1. T. Hashimoto et al. Hand Before Foot? cortical somatotopy suggests manual dexterity is primitive and evolved independently of bipedalism. Philosophical Transactions of the Royal Society B, 2013 DOI: 10.1098/rstb.2012.0417

Cite This Page:

RIKEN. "What evolved first, a dexterous hand or an agile foot?." ScienceDaily. ScienceDaily, 6 October 2013. <www.sciencedaily.com/releases/2013/10/131006204157.htm>.
RIKEN. (2013, October 6). What evolved first, a dexterous hand or an agile foot?. ScienceDaily. Retrieved August 21, 2014 from www.sciencedaily.com/releases/2013/10/131006204157.htm
RIKEN. "What evolved first, a dexterous hand or an agile foot?." ScienceDaily. www.sciencedaily.com/releases/2013/10/131006204157.htm (accessed August 21, 2014).

Share This




More Fossils & Ruins News

Thursday, August 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Neanderthals Probably Died Out Earlier Than We Thought

Neanderthals Probably Died Out Earlier Than We Thought

Newsy (Aug. 21, 2014) — A new study is packed with interesting Neanderthal-related findings, including a "definitive answer" to when they went extinct. Video provided by Newsy
Powered by NewsLook.com
Disquieting Times for Malaysia's 'fish Listeners'

Disquieting Times for Malaysia's 'fish Listeners'

AFP (Aug. 19, 2014) — Malaysia's last "fish listeners" -- practitioners of a dying local art of listening underwater to locate their quarry -- try to keep the ancient technique alive in the face of industrial trawling and the depletion of stocks. Duration: 02:29 Video provided by AFP
Powered by NewsLook.com
Mother And Son Find Woolly Mammoth Tusks 22 Years Apart

Mother And Son Find Woolly Mammoth Tusks 22 Years Apart

Newsy (Aug. 15, 2014) — A mother and son in Alaska uncovered woolly mammoth tusks in the same river more than two decades apart. Video provided by Newsy
Powered by NewsLook.com
Fossils Reveal Ancient Flying Reptile With 'Butterfly Head'

Fossils Reveal Ancient Flying Reptile With 'Butterfly Head'

Newsy (Aug. 14, 2014) — Newly found fossils reveal a previously unknown species of flying reptile with a really weird head, which some say looks like a butterfly. 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