Featured Research

from universities, journals, and other organizations

How 2-million-year-old ancestor moved: Sediba's ribcage and feet were not suitable for running

Date:
April 11, 2013
Source:
University of Zurich
Summary:
Researchers have described the anatomy of a single early hominin in six new studies. Australopithecus sediba was discovered near Johannesburg in 2008. The studies demonstrate how our 2-million-year-old ancestor walked, chewed and moved.

Reconstruction of Au. sediba.
Credit: Lee Berger; University of Witwatersrand

Researchers at Wits University in South Africa, including Peter Schmid from the University of Zurich, have described the anatomy of a single early hominin in six new studies. Australopithecus sediba was discovered near Johannesburg in 2008. The studies in Science demonstrate how our 2-million-year-old ancestor walked, chewed and moved.

The fossils discovered four years ago in Malapa near Johannesburg show a mixture of primitive features of australopiths and advanced features of later human species. The researchers led by Prof Lee Berger of Wits University are therefore of the opinion that the new species is currently the best candidate for a direct ancestor of our own genus Homo. Researchers are now presenting new studies, including those of Peter Schmid, who taught and did research at the University of Zurich until he retired. Also involved were UZH students Nakita Frater, Sandra Mathews and Eveline Weissen.

Schmid has described the remains of Au. sediba's thorax. "They show a narrow upper ribcage, as the large apes have such as orangutans, chimpanzees and gorillas," says Peter Schmid. The human thorax on the other hand is uniformly cylindrical. Along with the largely complete remnants of the pectoral girdle, we see the morphological picture of a conical ribcage with a raised shoulder joint, which looks like a permanent shrug. The less well-preserved elements of the lower thorax on the other hand indicate a slim waist, similar to that of a human being.

Conical ribcage makes it difficult to swing arms when walking

The narrow upper thorax of apes enables them to move the shoulder blade, which is important for climbing and brachiation in trees. Its conical shape makes it difficult, however, to swing their arms when walking upright or running, plus they were a similar length to an ape's. This is why Schmid assumes that Au. sediba was not able to walk or run on both feet as well as humans. "They probably couldn't run over longer distances, especially as they were unable to swing their arms, which saves energy," says Schmid.

An examination of the lower extremities shows a heel, metatarsus, knee, hips and back, which are unique and unprecedented. Sediba must have walked with feet turned sharply inwards. This inward turn distinguishes it from other australopiths. The conclusion to be drawn is that our early ancestors were able to move around in a different way.

Arms for climbing and brachiation

Au. sediba was an experienced climber. This is shown by the remains of the upper arm, radius, ulna, scapula, clavicle and fragment of sternum found in Malapa. These clearly belong to a single individual, which is unique in the entire previously known fossil record of the earliest hominins. With the exception of the hand bones described above, the upper extremity is exceptionally original. Au. sediba, like all the other representatives of the Australopithecus genus, had arms that were suitable for climbing as well as possibly for brachiation. Perhaps this capability was even more pronounced than has been assumed for this genus hitherto.

Differences from Australopithecus afarensis

Based on the dental crowns the researchers assume that Au. sediba does not belong phylogenetically to the eastern African australopiths but is closer to Au. africanus and thus forms a southern African sister group. This has an impact on our modern understanding of the evolution of early hominins from the late Pliocene. As such, Au. sediba and maybe even Au. africanus were not descended from Au. afarensis.

The lower jaw of the female skeleton was also examined along with previously unknown incisors and premolars. As noted already on the skull and other areas of the skeleton, the mandibular remains show similarities with other australopiths. They differ, however, in size and shape as well as in ontogenetic growth changes of Au. africanus. These results support the hypothesis that Au. sediba is taxonomically different from Au. africanus. In the relevant differences the parts of the lower jaw appear most to resemble those representatives of early Homo.

An analysis of the cervical, thoracic, lumbar and sacral region of the spinal column shows that Au. sediba had the same number of lumbar vertebrae as modern man. The strong hollow back suggests that he was more advanced in this area than Au. africanus and may be more likely compared with Homo erectus.

The new studies show a unique image of a human species with a mosaic-like physique. Some body parts are similar to those of earlier and others to those of later hominins. "The numerous similarities with Homo erectus suggest that Au. sediba represents the most appropriate early form of the genus Homo," says Peter Schmid. The previous candidates are too fragmentary to be capable of occupying this position.


Story Source:

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


Journal Reference:

  1. P. Schmid, S. E. Churchill, S. Nalla, E. Weissen, K. J. Carlson, D. J. de Ruiter, L. R. Berger. Mosaic Morphology in the Thorax of Australopithecus sediba. Science, 2013; 340 (6129): 1234598 DOI: 10.1126/science.1234598

Cite This Page:

University of Zurich. "How 2-million-year-old ancestor moved: Sediba's ribcage and feet were not suitable for running." ScienceDaily. ScienceDaily, 11 April 2013. <www.sciencedaily.com/releases/2013/04/130411142942.htm>.
University of Zurich. (2013, April 11). How 2-million-year-old ancestor moved: Sediba's ribcage and feet were not suitable for running. ScienceDaily. Retrieved September 23, 2014 from www.sciencedaily.com/releases/2013/04/130411142942.htm
University of Zurich. "How 2-million-year-old ancestor moved: Sediba's ribcage and feet were not suitable for running." ScienceDaily. www.sciencedaily.com/releases/2013/04/130411142942.htm (accessed September 23, 2014).

Share This



More Fossils & Ruins News

Tuesday, September 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Ice Age Wooly Mammoth Remains for Sale

Raw: Ice Age Wooly Mammoth Remains for Sale

AP (Sep. 23, 2014) A rare, well-preserved skeleton of a woolly mammoth is going on sale at Summers Place Auctions hope the 11.5-foot tall, almost intact specimen will fetch between $245,000 to $409,000. (Sept. 23) Video provided by AP
Powered by NewsLook.com
Dinosaur With Mysteriously Large Nose Discovered In Utah

Dinosaur With Mysteriously Large Nose Discovered In Utah

Newsy (Sep. 23, 2014) Rhinorex condrupus had a nose so big it was dubbed "King Nose," but scientists aren't sure what purpose it served. Video provided by Newsy
Powered by NewsLook.com
Iconic 'Easy Rider' Chopper Bike to Go on Auction Block

Iconic 'Easy Rider' Chopper Bike to Go on Auction Block

AFP (Sep. 19, 2014) The iconic Harley-Davidson motorbike ridden by Peter Fonda in the 1969 classic "Easy Rider" is to go under the hammer in California, and auctioneers predict it will make at least $1 million. Duration: 01:09 Video provided by AFP
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

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