East African grasslands influenced human evolution

Grasslands dominated the cradle of humanity in east Africa longer and more broadly than thought, says a study published Thursday, bolstering the idea that the rise of such landscapes shaped human evolution.

According to the so-called "savannah hypothesis", the gradual transition from dense forests into grasslands helped drive the shift toward bipedalism, increased brain size and other distinctively human traits.

First outlined in the 1920s, the theory suggests that our most ancient upright ancestors learned to walk on two feet, in part, to peer over tall grass in search of prey and predators.

Rather than simply plucking fruit from trees, they had to become shrewd hunters and move longer distances in order to survive.

The notion has been debated for more than a century, however, with some scientists saying other forces were more important in driving humans to assume their signature posture.

They also point to studies showing that the landscapes of the two regions of east Africa richest in hominid fossils -- the Awash Valley and The Omo-Turkana Basin, both in Ethiopia -- were in fact quite diverse in terms of tree cover.

One of the most complete early hominin species yet discovered, Ardipithecus ramidus, for example, may have lived primarily inside woodlands and patches of forest, they argue.

Hominins include early humans and pre-humans, along with the early ancestors of chimpanzees andgorillas.

The new study, published in Nature, will not settle the debate, but it offers evidence that savannahs -- with their limited tree cover -- stretched back even beyond the five million-year boundary widely assumed up to now, especially in areas populated by our distant forebear.

"There have been open habitats for all of the last six million years in the environments in eastern Africa where some of the most significant early human fossils were found," said Thure Cerling, a professor at the University of Utah and lead researcher of the study.

"Wherever we find human ancestors, we find evidence for open habitats similar to savannahs -- much more open and savannah-like than forested," he said in a statement.

Combining an analysis of soil samples and satellite photos of tropical regions around the world, the researchers created vegetation chronologies for the regions home to many hominin fossils, including Ardipithecus, Australopithecus, Paranthropus and our own genus, Homo.

During the past 7.4 million years woody cover has ranged from 75 to five percent, they found.

But significant areas of savannah -- below 40 percent wood cover -- were consistently present "all the time for which we have hominin fossils in the environments where the fossils were found during the past 4.3 millions years," thus including the oldest human ancestors, Cerling said.

Up to now, many scientists believe that East Africa was forested up until two million years ago, he added.

"This study shows that during the development of bipedalism -- about four million years ago -- open conditions were present and even predominant," Cerling said.

Ardi, your 4.4 million year old ancestor

The archaeological world was rocked this week when scientists announced the discovery of a 4.4 million year old fossil skeleton; the oldest prehuman remains ever discovered.  Ardi, short for Ardipithecus ramidus represents an exciting piece of our evolutionary past by possessing both human and primate traits. "She's not a chimp. She's not a human. She shows us what we used to be," said paleoanthropologist Tim White of the University of California-Berkeley. Before Ardi's discovery, Lucy, a 3.8 million year old Australopithecus afarensis, was the oldest early human skeleton yet discovered. Experts believe this new discovery is very, very close to the 'missing link' common ancestor of humans and chimps, thought to have lived 5 to 7 million years ago.

The fossils were found in what is known as the Middle Awash, a site in Ethiopia's Afar Rift, northeast of the capital city of Addis Ababa. The rift is a large triangular depression, where sediments have been accumulating for millions of years. Now parched desert, the landscape was once wet and heavily wooded, with fresh water springs and forests teeming with wildlife.

The first glimpse of Ardi came in 1992 when a former UC Berkeley grad student discovered a tooth among desert pebbles. In 1994, two pieces of a bone from the palm of a hand were discovered by another student. It snowballed from there, leading to the discovery of 110 other skeletal fragments, as well as 150,000 specimens of fossil plants and animals. But the bones were in terrible condition, trampled and scattered so bad that what remained of the skull measured a mere two inches in height. So entire blocks of fossil-rich rock were moved to the National Museum of Ethiopia in Addis Ababa. It took years to remove the clay from the fragile fossils. Ardi's fossilized remains were very fragile, sometimes disintegrating when they were touched.

No doubt the coming months will be filled with much debate over the theories behind this new discovery.  In the meantime, bask in the glow of that which is sexy archaeology!

All of the exciting research can be found in the October 2nd edition of the journal Science.

Not a subscriber?  No worries.  Head over to the AAAS website where all 11 papers pertaining to this new discovery are available online for free.

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Here's what you need to know about Ardi:

• Full name Ardipithecus ramidus.


• The remains were discovered in Ethiopia's harsh Afar desert.


• Volcanic layers around the fossil were used to date it from 4.4 million years ago.


• Ardi's upper canine teeth are more similar to stubby human teeth than sharp chimpanzee teeth.


• Tooth enamel analysis revealed they ate fruit, nuts and leaves.


• Ardi's brain was positioned in a similar way to that of humans.


• The pelvis and hip show the gluteal muscles were positioned so she could walk upright.

The Spaz Speaks: Seeeexxxaaaayyy....

Check this stuff out. Look at that long coat. Those beautiful eyes. Sexxxxxaaaayyy! Darn, if she were any hotter I'd be climbing trees.

Now that that is out of the way, I just wanted to take this break from reading Erich von Daniken's... riveting... book to bring to you "The Missing Link." Or maybe not, but we're at least a step closer.

Personally, I've always been more attracted to those habilis ladies. Mmmmm.... love me some prognothism and brow ridge.