Who Was Ardipithecus Ramidus (ARDI)?
The completeness of Ardi's remains, as well as the more than 150,000 plant and animal fossils collected from surrounding sediments of the same time period, has generated an unprecedented amount of intelligence about one of our earliest potential forebears.
The path of just such a discovery began in November 1994 with the unearthing of two pieces of bone from the palm of a hominid hand in the dusty Middle Awash region of Ethiopia.
Within weeks, more than 100 additional bone fragments were found during an intensive search-and-reconstruction effort that would go on for the next 15 years and culminate in a key piece of evolutionary evidence revealed this week: the 4.4 million–year–old skeleton of a likely human ancestor known as Ardipithecus ramidus (abbreviated Ar. ramidus).
Ardi is the earliest and best-documented descendant of that common ancestor. But despite being "so close to the split," says White, the surprising thing is that she bears little resemblance to chimpanzees, our closest living primate relatives. The elusive common ancestor's bones have never been found, but scientists, working from the evidence available — especially analyses of Australopithecus and modern African apes — envisioned Great-Great-Grandpa to have looked most nearly like a knuckle-walking, tree-swinging ape. But "[Ardi is] not chimplike," according to White, which means that the last common ancestor probably wasn't either.
"This skeleton flips our understanding of human evolution," says Kent State University anthropologist C. Owen Lovejoy, a member of the Middle Awash team. "It's clear that humans are not merely a slight modification of chimps, despite their genomic similarity." (TIME magazine »)
Protein - Darwinian Evolution Theory In Reverse
In 2009, Thornton’s group ruled out evolution in reverse, discovering that once a protein supposedly arrives, no natural processes can morph it back to a prior version. That’s because the stepwise changes required to convert the current functional version of a protein back to its supposedly ancestral protein rendered the “transitional proteins” useless in the group’s lab experiments.
Biochemist Michael Behe, who was not involved in the study, wrote for Evolution News, “To the extent that a pre-existing system had to pass through improbable, unselected, or even detrimental states—unguided by natural selection or any other unintelligent factor—to reach a rare new function, then to that extent we can say Darwinian evolution does not explain life." And if Darwinian evolution does not explain as small a step as evolving a new version of a single protein, then why would anyone expect it to explain the evolution of all the new proteins required to transform a protozoan into a person?