LONG-HELD assumptions about the evolution of humans have been challenged following a detailed analysis of a fossil skeleton dating back 4.4 million years.
The ape-like creatures from which we evolved most likely did not learn to walk on two legs by hiking across the open African savannah. Nor can we make assumptions about what our “missing link” ancestor looked like by studying modern apes, the new research suggests.
An astounding amount of new data and theories have flowed from an extensive study of the partial skeleton of a human-like or hominid creature called Ardipithecus ramidus. The first detailed analysis of what the fossils revealed is published this morning in the journal Science.
Nicknamed “Ardi” for short, the skeleton and assorted bits from another 35 individuals were found during the mid-1990s. All came from the Afar Rift of northeast Ethiopia.
Ardi stood about 1.2 metres high and weighed a chunky 50kg. She predates the celebrity hominid “Lucy”, who dates to only 3.2 million years.
Apish Lucy was assumed to be an intermediate link between modern humans and ancient apes, but Ardi has so many “modern” characteristics that scientists have had to rethink their views on the progress of hominid evolution.
Ardi is an older fossil with plenty of “primitive” ape-like characteristics, but also a number of uniquely hominid features shared only with others like ourselves.
It walked upright and without the side-to-side gait seen in modern apes. And even though its arms were long it wasn’t a “knuckle-walker”.
It didn’t hang or swing in the trees like today’s apes, and while its feet did retain an opposable big toe, the foot itself was stiffer and better suited for walking. “It is so rife with anatomical surprises that no one could have imagined it without direct fossil evidence,” the authors write.
Particularly noteworthy were Ardi’s canine teeth, not big and sharp like an ape but short and stubby like our own canines. The authors believe this shows A. ramidus males did not battle for access to fertile females but formed male-female pair bonds.
Ardi lived in a cool, humid woodland rather than the hot savannah, an analysis of plant fossils showed. And this afforded plenty of fruit, nuts, insects and small mammals and birds for Ardi and her kind to gather, either in the trees or on the ground.
Scientists are now re-examining human origins in light of Ardi. The long-standing view was that we could look to chimps and gorillas to understand what our last common ancestor with apes must have looked like.
Ardi “nullifies these presumptions” because it shows the anatomy of living apes is not primitive but the result of extensive evolutionary adaptation since the hominid and ape lines finally split about six million years ago.