Scientists found fossils
that are 4.4 milion years old and were able to reconstruct the skeleton of a 4-foot
female hominid, or member of the primate family, that they named "Ardi," short
for Ardipithecus ramidus.
Ardi predates the famous 3.2
million year old "Lucy," a skeleton of the human-like genus Australopithecus.
The new find, published by the journal Science, gives more
evidence to the theory that chimps and humans evolved from a common ancestor.
Lucy prompted scientists to believe that the shared ancestor of humans and apes
looked like a chimp, but Ardi has many human-like features.
"This is not
that common ancestor, but it's the closest we have ever been able to come," said
leader of the excavation team Tim White, of the University of California, Berkeley.
is a landmark, said Dean Falk, an evolutionary anthropologist according to Wired
Magazine. "The field will go into a frenzy."
Who was Ardi?
Ardi was found in Ethiopia, and fossils found with the skeleton suggest it lived
in the forest.
Scientists have spent 17 years
studying the significance of Ardi's bones before publishing their first complete
analysis of the specimen.
Over 125 pieces of Ardi's skeleton were found
in Ethiopia, including important bones like the skull, arms, hands and legs.
study of the bones shows that Ardipithecus ramidus lived in forest and
could walk upright, but also use all four limbs to climb tree branches. Her brain
was about the size of a modern-day chimps and her feet had no arches, unlike Lucy
and today's humans.
Ardi's face had an ape-like appearance, but a close
examination of her skull shows that her brain was positioned similarly to humans,
paving the way for growth in areas associated with visual and spatial perception
in the brain.
The discovery changes perceptions about the environment
that ancient human ancestors might have inhabited. Soil deposits and other plant
and animal fossils collected at the site suggest that Ardi lived in the forest,
while Lucy was a creature of the savanna desert plains.
When did humans
and chimps separate?
Before the discovery of Ardi, scientists thought human ancestors looked like Lucy,
and before that, a chimpanzee. That conclusion was incorrect.
According to the researchers,
the discovery sheds light on many unresolved questions about "the initial stage
of evolutionary adaptation" after the hominid group separated from chimps.
While Ardi is not believed to be humankind's last common ancestor with
chimps, scientists believe that they are getting closer to that find, a species
that could have existed as far back as nine million years ago.
"Lucy" represents another key stage with the genus Australopithecus because of
her sophisticated walking ability. Her genus is then followed by the group Homo
- the genus of the modern-day human - over two million years ago.
search for the last common ancestor
Scientists have long sought for a species that served as the last common ancestor
between apes and humans.
Since Darwin first theorized
that humans and apes shared a common lineage, the scientific community has been
on the hunt for physical evidence of that last common ancestor, sometimes referred
to as the LCA.
Charles Darwin became the first scientist to provide an
explanation for similarities between all of earth's living creatures with his
seminal work, "On the Origin of Species," in 1859. He was the first to argue
that all living things come from a shared ancestor from which species evolved
over millions of years.
At the time of its publication, Darwin’s
book was considered radical because his theories contradicted the biblical belief
that God created man in six days. To this day, many people continue to challenge
Darwin’s basic premise that human beings evolved from other animals, specifically