Key Genetic Changes in Human Pelvis Enabled Upright Walking

The ability to walk upright on two legs is a defining characteristic of humans, setting us apart from other primates. Recent research has shed light on the evolutionary changes in the human pelvis that made bipedalism possible.

A study published in Nature identified two significant genetic changes that reshaped the human pelvis. The first change involved a 90-degree reorientation of the ilium, the largest bone in the pelvis, during embryonic development. This alteration transformed the ilium from a tall, narrow structure to a short, wide one, providing attachment points for gluteal muscles essential for upright walking .

The second change was a delay in the ossification process of the pelvis, allowing it to maintain its shape as it grew. This adaptation not only facilitated bipedal locomotion but also accommodated the passage of larger-brained infants during childbirth .

These evolutionary modifications were driven by over 300 genes, with three—SOX9, PTH1R, and RUNX2—playing pivotal roles. Mutations in these genes can lead to skeletal disorders affecting the pelvis and walking ability .

The study’s findings suggest that these genetic shifts occurred between 5 and 8 million years ago, coinciding with the divergence of the human lineage from other primates . Fossil evidence, such as the pelvis of Ardipithecus ramidus dating back 4.4 million years, indicates that these pelvic changes were present in early human ancestors .

Understanding these evolutionary changes provides insight into how our ancestors adapted to bipedalism and the challenges of childbirth, highlighting the intricate relationship between anatomy, genetics, and evolution.

Featured image: The hominoids are descendants of a common ancestor. (Public Domain)