Uncovering the Genes That Let Our Ancestors Walk Upright

        Charles Darwin is widely known for developing ideas of evolution by natural selection, and he extended his ideas in relation to humans in his book. He released "The Descent of Man", in 1871, where he argued the cause of humans evolving from our ancestors, the ape. He argued one of the biggest changes being upright walking in humans. This bipedalism is now known as one of the most defining characteristics of humanity.

    However, since Darwin's monumental discovery, there's been some more breakthroughs in how exactly this happened on a molecular level. It was hypothesized that it was not because new genes arose, but because old genes began doing new things, meaning some genes became active in humans.

                   Comparison of skeletons from "Evidence as to Man's Place in nature," by Thomas Henry Huxley, 1863.

    A key feature to humans walking upright is the ilium bone. The bone is responsible for walking, supporting organs, and childbirth. The bone is fused to the base of the spine, goes around the waist, and in front of the belly. The development of the ilium is a mystery still though, very little is known about its origin. After much in depth research on 18 different primate species, it has been found that in human embryos, the ilium begins as a single rod that forms perpendicular to the spine. But for most species studied, the ilium begins as two cartilage rods parallel to the spine. Humans have the same gene to form the bone, but in humans it activates in a different manner. This change in bone structure is what has allowed for humans to develop a pelvis that is strong enough and suitable for bipedalism. 

    Another discovery involved a second evolutionary change, being that the ilium turns from cartilage to bone much later than the rest of the human skeleton, by about 15 weeks. It is hypothesized that this evolved about 1 million years ago following the growth of the human brain, which required a larger birth canal to support the larger babies' heads.

    This discovery about the origin of bipedalism in humans is a huge milestone in the understanding of human evolution. It is so awesome that it was seen that the same gene in humans was also found in other apes, but those same genes became active in new ways that led to bipedalism in humans.

References:

Wobser, A. M. (2023, July 24). Anatomy, abdomen and pelvis: Bones (ilium, ischium, and pubis). StatPearls [Internet]. https://www.ncbi.nlm.nih.gov/books/NBK519524/

Zimmer, C. (2025, August 27). Uncovering the genes that let our ancestors walk upright - The New York Times. https://www.nytimes.com/2025/08/27/science/human-evolution-ilium-bipedal.html