After 15 years of rumors, researchers in the U.S. and Ethiopia on Thursday made public fossils from a 4.4-million-year-old human forebearer they say reveals that our earliest ancestors were more modern than scholars assumed and deepens the evolutionary gulf separating humankind from today’s apes and chimpanzees.
The highlight of the extensive fossil trove is a female skeleton a million years older than the iconic bones of Lucy, the primitive female figure that has long symbolized humankind’s beginnings.
[Click to continue reading Fossils Shed New Light on Human Origins – WSJ.com]
Documented in 11 research papers to be published Friday in the journal Science, the fossils offer a detailed look at a species of sturdy, small-brained creatures that dwelled in an ancient African glade of hackberry, fig and palm trees, by a river that long ago turned to stone. Despite their antiquity, their bodies were already starting to presage humanity, the scientists said.
Indeed, unlike apes and chimps, they had supple wrists, strong thumbs, flexible fingers and power-grip palms shaped to grasp objects like sticks and stones firmly. They were primed for tool use, even though it would be another two million years or so before our ancestors began to fashion the first stone blades, choppers and axes.
But they were still evolving the ability to walk upright, with a big toe better suited for grasping branches than stepping smartly along, an analysis of their anatomy shows. They made their home in the woods, not on the open savannah grasslands long considered the main arena of human development. Yet their upright posture, distinctive pelvis and other toes suggest they walked easily enough. Most importantly, they showed no sign they walked on their knuckles, as contemporary chimps and apes do.
“They are not what one would have predicted,” said anthropologist Bernard Wood at George Washington University. Although the differences between humans, apes and chimps today are legion, we all shared a common ancestor six million years or so ago. These fossils suggest that creature–still undiscovered–resembled a chimp much less than researchers have always believed.
Note, these photos are mine, and have nothing to do with the new fossil discoveries.
From the Ann Gibbons article at Science:
Researchers have unveiled the oldest known skeleton of a putative human ancestor–and it is full of surprises. Although the creature, named Ardipithecus ramidus, had a brain and body the size of a chimpanzee, it did not knuckle-walk or swing through the trees like an ape. Instead, “Ardi” walked upright, with a big, stiff foot and short, wide pelvis, researchers report in Science. “We thought Lucy was the find of the century,” says paleoanthropologist Andrew Hill of Yale University, referring to the famous 3.2-million-year-old skeleton that revolutionized thinking about human origins. “But in retrospect, it was not.”
Researchers have long argued about whether our early ancestors passed through a great-ape stage in which they looked like protochimpanzees, with short backs; arms adapted for swinging through the trees; and a pelvis and limbs adapted for knuckle-walking (Science, 21 November 1969, p. 953). This “troglodytian,” or chimpanzee, model for early human behavior (named for the common chimpanzee, Pan troglodytes) suggests that our ancestors lost many of the key adaptations still found in chimpanzees, bonobos, and gorillas, such as daggerlike canines and knuckle-walking, which those apes were thought to have inherited from a common ancestor.
[Click to continue reading Ancient Skeleton May Rewrite Earliest Chapter of Human Evolution — Gibbons 2009 (1001): 1 — ScienceNOW]
- the Creationists [↩]