Newly Discovered Ape Fossil May Explain How Early Humans Started Walking Upright On Two Feet

The 21 bones of the most complete partial skeleton of a male Danuvius. Christoph Jäckle

The fossilized remains of an ancient ape that lived more than 11 million years ago during the Miocene may help us understand how and when early humans began walking on two legs, shaping the course of evolution for generations to come.

The complete preserved limbs of Danuvius guggenmosi were found in the mountainous Allgäu region of Bavaria in southern Germany. Writing in Nature, researchers characterize the remains as a “broad thorax, long lumbar spine and extended hips and knees, as in bipeds, and elongated and fully extended forelimbs, as in all apes. Danuvius combines the adaptations of bipeds and suspensory apes, and provides a model for the common ancestor of great apes and humans.”

Their unique physiological makeup suggests D. guggenmosi would have been able to hang from branches by its arms like an orangutan, while its legs would have allowed them what researchers have termed “extended limb clambering”. Unlike modern apes such as orangutans or gibbons, which use their arms more than legs for movement, this species had hindlimbs that were held straight for walking on as well as a grasping big toe that indicates it would have walked on the soles of its feet.

“Many ideas have been proposed to explain the origin of bipedalism in hominins and suspension in great apes (hominids); however, fossil evidence has been lacking,” write the authors in Nature. Two overarching theories generally dominate the evolution of bipedalism. Either two-legged hominids evolved from four-legged primates that put their feet down on the ground like modern monkeys to eventually adapt upright, or early hominids were similar to a species of now-extinct chimpanzees that were suspensory quadruped.

If the new theory is accepted, an accompanying article written in Nature notes that D. guggenmosi will contribute to our understanding of the course of early human evolution. The 4.4-million-year-old remains of a female Ardipithecus ramidus walked on two feet and was more closely related to early humans than apes. Other bipedalism has been seen between 6 and 7 million years ago, and humans and modern chimpanzees diverged around the same time. D. guggenmosi suggests that bipedalism may have shown up before hominins split from modern chimpanzees and bonobos.

“What makes things really complex now is, what defines hominins if not habitual bipedalism?” study author and palaeoanthropologist Madelaine Böhme told the publication. “Our paper may create a dilemma for the definition of hominins.”

But not everyone is convinced. Other researchers contest the theory, arguing that bone shape alone is not enough to determine how an ape moved. Furthermore, they argue that not enough of the lower spine is preserved to understand if the lower back was long and flexible – requirements needed for walking upright.

Bones from the hand of a male Danuvius. Christoph Jäckle

 

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