Back pain is the largest contributor to disability worldwide, according to the most recent Global Burden of Disease study. This comes as no surprise to health practitioners, but why do so many of us suffer from back pain? Researchers suggest that evolutionary biology can help us to unravel the mysteries of lower back pain.
Lower back pain affects people of all ages, but according to the World Health Organization (WHO), the cause of the onset of lower back pain remains “obscure.” Kimberly Plomp, a human evolution researcher in the Department of Archaeology at Simon Fraser University, tells IFLScience that there are many different factors, including human evolution “that could influence whether someone is going to develop pathologies that would lead to back pain.”
“Evolution is not perfect. A big misconception about evolution is that it’s continuing along a line that has an aim or a goal and it’s not like that at all,” Plomp adds.
The human ancestors walked on all fours, which helped them to climb trees and get around diverse habitats, according to the Smithsonian’s National Museum of Natural History. Over time that behavior gradually changed, and fossils show us that by around four million years ago, early human species were “mostly bipedal,” which allowed them to take advantage of both near open areas and dense woods. By around 1.9 million years ago, when the environment was “fluctuating wildly between moist and dry,” early humans had become “fully bipedal” and had evolved a uniquely human curved spine. The timeline of the evolution of upright walking is, however, much better understood than why bipedalism evolved.
Plomp explains that the “rapid” evolution of humans' ability to walk on two legs may have a significant impact on human health. The gain of humans walking upright might have come with its own set of pain – namely in the lower back. Our knuckle-walking ape cousins are thought to suffer less from back pain as they don't have the extra stress placed on their back from upright walking.
In a recent study, published in BMC Evolutionary Biology, Plomp studied the spine shapes of chimpanzees, orangutans and both modern and ancient humans. She found that people whose spines were most similar to chimps were more likely to have a small lesion that forms in the disc between vertebrae in the lower back, causing pain.
Plomp is quick to point out that the study was small, but says that it adds to a growing school of thought that our upright posture could be placing more stress on our spine, making it a contributing factor to lower back pain. Plomp also explains that those with spines more similar to chimpanzees still had spines “well within the range of normal human variations.”