Early hominins' walk was as energetic as modern humans: study

The walk of hominins in the Pleistocene era was no less efficient energetically than that of present-day humans, a study has found.

Researchers analysed the influence of body proportions on the cost of locomotion by means of an experimental energetic study with 46 subjects of both sexes.

The results, published in the American Journal of Physical Anthropology, indicate that the walk of hominins in Pleistocene - which lasted from about 2,588,000 to 11,700 years ago - was no less efficient energetically than that of present-day humans.

Researchers at Centro Nacional de Investigacion sobre la Evolucion Humana (CENIEH) in Spain used the relationship between the width of the hip, the length of the femur and the body mass to model this cost in a large number of extinct hominins.
 

Traditionally, it was thought that the leaner skeletons of modern humans reflected biomechanical advantages which made locomotion a more efficient activity.

The slimmer pelvis of our species entails greater difficulty for childbirth, but it reduces the force the abductor muscles of the hip have to exert to maintain the stability of the pelvis while walking.

"That does not imply that the hominins with wider pelvises expend more energy walking," said Marco Vidal Cordasco, lead author of the study.

"In fact, the results obtained show that wider pelvises, at the height of the iliac crest, allow the energy cost of locomotion to be significantly lower," said Cordasco.

Since two million years ago, with the appearance of the species Homo ergaster, the body mass and the brain size of the hominins have risen considerably, researchers said.

These changes have entailed an important readjustment at the metabolic level, with greater demand for energy to maintain these larger organs, they said.

"However, our results show that the greater efficiency of locomotion was not a mechanism to compensate for this increase in size," Cordasco said.

"That is to say, the changes observed in the width of the pelvis and the length of the lower limbs did not reduce the cost of walking sufficiently to offset the rise in energy cost caused by the increased body mass," he said.