Foot fossils suggest hominins walked on two feet earlier than thought

Aug. 15 (UPI) -- Ancient forefoot joints suggest bipedalism emerged among hominins earlier than paleontologists previously thought.

Apes are really good at grasping objects with their feet. They can even use them to peel and eat bananas. But as hominin transitions from the tree tops to the flat savannah surface, the benefits of walking upright outweighed the ability to grasp, and forefoot joints evolved.

Recently, scientists at Stony Brook University analyzed dozens of fossil forefoot joints belonging to hominins, apes, monkeys and humans.

They researchers showed a structural shift among the fossils, essential for bipedalism, emerged earlier than previously thought. Scientists pinpointed the dorsal head expansion and "doming" of the metatarsal heads that differentiate hominin toe joints from those of apes.

Paleontologists detailed their analysis in the journal PNAS this week.

"We have identified novel bony shape variables in the forefoot across extant anthropoids and extinct hominins that are linked functionally to the emergence of bipedal walking," researchers wrote.

Previous research by scientists at Stony Brook showed that an adoption of bipedalism precipitated other skeletal shifts, including changes in skull design.

An earlier study found hominins developed a forward-shifted foramen magnum, the hole in the bottom of the skull through which the spinal cord passes. Scientists believe the adaptation ensured the brain remained centered over the spine.