Our bones are much lighter and weaker than those of our Paleolithic ancestors (11,000 to 33,000 years ago), but it's not our spoiled modern day lifestyle that's to blame. Instead, a new study which closely compared homo sapiens bones, both ancient and modern, found that the most significant changes occurred once the paradigm shift from hunter-gatherer to agriculture took place, some 10,000 years ago. Humans started forming permanent settlements, worked the land and tended to flocks. Consequently, the lifestyle became more sedentary.
One might argue that's nothing compared to we're seeing in modern society. Today, one third of the population is obese, so it would seem reasonable to believe that our bones should have became even frailer in the meantime. However, according to lead researcher Christopher Ruff, professor in the center for functional anatomy and evolution at the Johns Hopkins University School of Medicine, the differences in bone strength between Mesopotamian farmers and 20th century humans are minimal to negligible. To gives to show just how strong our hunter-gatherer ancestors were, especially in the lower limbs.
Ruff and colleagues analyzed bones from 1,842 people collected from all over Europe from the Paleolithic period to the 20th century. The focus was on the long bones in the arms and legs, while arm strength was gauged for control. The differences in arm bones between hunter-gatherers and Mesopotamians weren't at all noticeable. However, when it came to lower limb bone strength that was another story. The front-to-back bending strength of the leg bones was considerably greater during the Paleolithic, while side-to-side strength changed very little. Since the front-to-back bending strength is a prime indicator of mobility, and considering arm bone strength stayed more or less constant across the ages, the researchers reason that any loss of bone strength resulted from foregoing a migrating lifestyle. If a change in diet caused a change in bone structure or strength, we should had seen this across all bones - both arm and leg bones. This drop in bone strength in the lower limbs remained constant throughout the Iron Age and the Roman era, as well as in the 20th century.
“By the medieval period, bones were about the same strength that they are today,” the researchers note in Proceedings of the National Academy of Sciences.
This suggests that cars, airplanes and even TV dinner had minimal effects on changing leg bone density. Of course... maybe it's still too early to see the differences.
The research is important for its medical insights. For instance, bones became increasingly thinner and prone to fractures and osteoporosis almost 7,000 years ago during the last part of the Stone Age. It would have been interesting if the researchers also looked at contemporary leg bones coming from modern day hunter-gatherer people, like those still living as they have for thousands of years in Congo or the Australian outback. Maybe in the next installment.
In any event, the researchers note that these changes aren't genetic. In other words, you too could have leg bones as strong as Paleolithic hunter-gatherer, if you exposed yourself to the same stresses and lifestyle. True enough, it's enough to look at athletes today to see this happening.