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Ardi, shown here in an artist's sketch, is a recently discovered ancestor of man which lived 4.4 million years ago in African woodland. The discovery is the closest to a "missing link" found yet.  (Source: Time Magazine)

Ardi's skeleton graces the cover of the journal Science. While it may not look like much, the skeleton is among the most complete hominid skeletons found to date and an appealing find.  (Source: Science)
Newly discovered species is close to "missing link" and provides more compelling proof of human evolution

If there's one thing that recent paleontological discoveries have taught us, it's to expect the unexpected.  A recently discovered miniature T. Rex predecessor cast doubt on many theories, including the idea that T. Rex evolved its bizarre proportions (small arms, huge legs) over time (its ancestor had them too) and that it was a scavenger (the mini-Rex was fast and ideally suited for hunting).

Now an equally appealing discovery had been made.  Scientists excavating in the dusty Middle Awash region of Ethiopia have unearthed an amazingly complete skeleton of a new species of hominid -- an ancestor to modern man -- which they have named Ardipithecus ramidus, nicknamed "Ardi".

The find began in 1994 with the unearthing of a hominid hand. One and a half decades later, Ardi was revealed in her full form, a skeleton consisting of over 125 bone pieces.  Among the most complete hominid skeletons found to date, Ardi is approximately 4.4 million years old, 1.2 million years older than the famous "Lucy" (Australopithecus afarensis) skeleton.  Ardi is in fact the oldest hominid found to date.

Ardi is an irresistibly appealing find to most.  It provides unprecedented insight into how humans and apes diverged from a common ancestor approximately 7 million years ago -- closer to Ardi's time than we are to Ardi's.  And the discovery reveals a shocking revelation -- Chimpanzees and other close ape relatives might actually have evolved more radically than humans did over that 7 million years.

Kent State University anthropologist C. Owen Lovejoy, a member of the Middle Awash team, states, "This skeleton flips our understanding of human evolution.  It's clear that humans are not merely a slight modification of chimps, despite their genomic similarity."

Ardi is closer to humans than chimps.  Measuring in at 47 in. (120 cm) tall and 110 lb. (50 kg), Ardi likely walked with a strange gait, lurching side to side, due to lack of an arch in its feet, a feature of later hominids.  It had somewhat monkey-like feet, with opposable toes, but its feet were not flexible enough to grab onto vines or tree trunks like many monkeys -- rather they were good enough to provide extra support during quick walks along tree branches -- called palm walking.

However, most of Ardi's time was spent upright on the ground.  Long dexterous fingers showcase Ardi's humanlike characteristics; its wrists were also more flexible than apes.  These features helped it to catch things on the ground and carry objects.

Another surprise comes in Ardi's environment.  Ardi lived in a lush grassy African woodland, with creatures such as colobus monkeys, baboons, elephants, spiral-horned antelopes, hyenas, shrews, hares, porcupines, bats,  peacocks, doves, lovebirds, swifts and owls.  Fig trees grew around much of the area, and it is speculated that much of Ardi's diet consisted of these figs.

The surprise about the environment is that it lays to rest the theory that hominids developed upright walking when Africa's woodland-grassland mix changed to grassy savanna.  Under this now theory, hominids began standing and walking upright as a way of seeing predators over the tall grasses.  The discovery of Ardi -- an earlier upright walker that lived in woodland -- greatly weakens this theory.

Scientists have theorized that Ardi may have formed human-like relationships with pairing between single males and females.  Evidence of this is found in the male's teeth, which lack the long canines that gorillas and other non-monogamous apes use to battle for females.  Describes Professor Lovejoy, "The male canine tooth is no longer projecting or sharp. It's no longer weaponry."

There's still debate over parts of the creature's skeleton.  In particular, the pelvis was smashed and had to be extensively reconstructed using digital technology.  According to Penn State paleoanthropologist Alan Walker, who was not involved in the discovery, "Tim [White] showed me pictures of the pelvis in the ground, and it looked like an Irish stew."

Still, with over 110 remnants discovered from over 35 other Ardi's and a complete skeleton, the find is undeniably exciting.  States Professor Walker, "[Ardi is] a lovely Darwinian creature.  It has features that are intermediate between the last common ancestor and australopithecines."

And Professor Lovejoy adds, "When we started our work [in the Middle Awash] the human fossil record went back to about 3.7 million years.  This isn't just a skeleton; we've been able to put together a fantastic, high-resolution snapshot of a period that was a blank."





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