Scientists Explain: If We Evolved from Apes, Why Do Humans Stand Upright?

If humans evolved from apes, then why do humans stand upright, while they still use four legs? First off, humans and apes evolved from a common ancestor millions of years ago, and not from each other. Apes and chimpanzees, along with other primates, are more of our evolutionary cousins, but our paths diverged a long time ago.

So, why do we stand upright, while the majority of apes and closely related species still walk using their four legs? The simple and quick answer would be because of evolution and the unique path that ancient humans took. In other words, bipedalism was naturally selected millions of years ago, slowly progressing over time, because it helped our ancestors adapt to meet their needs to survive.

Bipedalism Began Millions of Years Ago

Although the modern human species, Homo Sapiens, has only existed for approximately 300,000 years, early hominins like Sahelanthropus and Orrorin, living 6–7 million years ago, already began walking upright. That is even before our brains developed to become larger, showcasing just how much nature and evolution favored this characteristic.

The first time a hominin species was recorded to have fully walked upright was about 3.7 million years ago, from fossil footprints in Laetoli, a paleoanthropological site in Tanzania. This tells us that our current human species was not the first one to adopt bipedalism.

Read more: Human Origins

Energy Efficiency and Survival Benefits

The Seven-Million-Year-Long Journey - Why Humans Stood Upright ~ with JEREMY DESILVA

So, now that we know that bipedalism began even before modern humans existed, it still begs the question as to why we started doing that in the first place. Some of the leading theories are our transition from living in the forest to various parts of the world, like open savanna and grasslands.

Studies suggest that the challenges and opportunities provided by such environments pressured our ancestors to walk upright and develop bigger brains, because of increased travel distances and a diet that involves hunting quick and fast animals.

Walking on two legs uses about 75% less energy than using all four, and this benefit allowed us to hunt persistently until we outrun other fast animals due to their exhaustion.

Freed Hands, Bigger Brains

After we learn to walk upright, our hands are freed to do other necessary tasks, such as carrying resources and using tools for hunting and daily activities. This evolutionary process led to the invention of technological innovations and new ways to gather food.

This is commonly referred to as provisioning, which pertains to the act of providing resources. Charles Darwin and other scientists believe this is a big part of why our brains developed to be bigger.

Over time, some more changes solidified in our anatomy, such as a wider pelvis, shortened arms, and better foot structure, which further refine our ability to walk and run on two legs.

Read more: National Library of Medicine

Evolutionary Trade-offs and Modern Cost

Bipedalism was crucial for our ancestors, and one could argue that if we had not learn it, we would not become who we are today. Without the ability to walk upright, our hands would not have been freed, provisioning would have changed, and our brains might not have developed to be bigger and better.

A typical evolutionary process where one thing led to another. However, it did not come without a cost. The trade-offs are still problems we face today, such as back pains, spinal diseases, and more issues that rarely occur in apes of today. Our bipedalism, although very efficient and necessary, placed a heavier pressure and stress on our spine and lower limbs.

Still, the benefits outweigh the cost as it has led us to this moment. Despite some of our population experiencing bad back pains and other trade-offs of bipedalism, we have reached the top of the food chain, and it has given rise to culture and civilization.

Why Do We Walk Upright? The Evolution Of Bipedalism

Author's Final Thoughts

Humans did not learn how to walk upright in just one or a few generations. It took us millions of years and countless different types of hominin species to perfect bipedalism. This trait gave us efficiency, environmental adaptation, and freed our hands, which all eventually set us on a path toward the humans of today.

Read more: Why Do Humans Have Back Pain? Evolution Left Us With a Problem We Still Carry Today

References & Further Reading

Lovejoy, C. O. (2009). Reexamining human origins in light of Ardipithecus ramidus. Science. https://doi.org/10.1126/science.1175834

Sockol, M. D., Raichlen, D. A., & Pontzer, H. (2007). Chimpanzee locomotor energetics and the origin of human bipedalism. PNAS. https://doi.org/10.1073/pnas.0703267104

Wheeler, P. E. (1991). The thermoregulatory advantages of hominid bipedalism in open equatorial environments. Journal of Human Evolution. https://doi.org/10.1016/0047-2484(91)90002-D

Leakey, M. D., & Hay, R. L. (1979). Pliocene footprints in the Laetolil Beds at Laetoli, northern Tanzania. Nature. https://doi.org/10.1038/278317a0

Ward, C. V. (2002). Interpreting the posture and locomotion of Australopithecus afarensis: Where do we stand? American Journal of Physical Anthropology (Yearbook). https://doi.org/10.1002/ajpa.10185