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Scientists Say the Future Looks Bleak For Our Bones
HughPickens.com writes Nicholas St. Fluer reports at The Atlantic that according to researchers, our convenient, sedentary way of life is making our bones weak foretelling a future with increasing fractures, breaks, and osteoporosis. For thousands of years, hunter-gatherers trekked on strenuous ventures for food with dense skeletons supporting their movements and a new study pinpoints the origin of weaker bones at the beginning of the Holocene epoch roughly 12,000 years ago, when humans began adopting agriculture. "Modern human skeletons have shifted quite recently towards lighter—more fragile, if you like—bodies. It started when we adopted agriculture. Our diets changed. Our levels of activity changed," says Habiba Chirchir. A second study attributes joint bone weakness to different levels of physical activity in ancient human societies, also related to hunting versus farming.
The team scanned circular cross-sections of seven bones in the upper and lower limb joints in chimpanzees, Bornean orangutans and baboons. They also scanned the same bones in modern and early modern humans as well as Neanderthals, Paranthropus robustus, Australopithecus africanus and other Australopithecines. They then measured the amount of white bone in the scans against the total area to find the trabecular bone density. Crunching the numbers confirmed their visual suspicions. Modern humans had 50 to 75 percent less dense trabecular bone than chimpanzees, and some hominins had bones that were twice as dense compared to those in modern humans. Both studies have implications for modern human health and the importance of physical activity to bone strength. "The lightly-built skeleton of modern humans has a direct and important impact on bone strength and stiffness," says Tim Ryan. That's because lightness can translate to weakness—more broken bones and a higher incidence of osteoporosis and age-related bone loss. The researchers warn that with the deskbound lives that many people lead today, our bones may have become even more brittle than ever before. "We are not challenging our bones with enough loading," says Colin Shaw, "predisposing us to have weaker bones so that, as we age, situations arise where bones are breaking when, previously, they would not have."
The team scanned circular cross-sections of seven bones in the upper and lower limb joints in chimpanzees, Bornean orangutans and baboons. They also scanned the same bones in modern and early modern humans as well as Neanderthals, Paranthropus robustus, Australopithecus africanus and other Australopithecines. They then measured the amount of white bone in the scans against the total area to find the trabecular bone density. Crunching the numbers confirmed their visual suspicions. Modern humans had 50 to 75 percent less dense trabecular bone than chimpanzees, and some hominins had bones that were twice as dense compared to those in modern humans. Both studies have implications for modern human health and the importance of physical activity to bone strength. "The lightly-built skeleton of modern humans has a direct and important impact on bone strength and stiffness," says Tim Ryan. That's because lightness can translate to weakness—more broken bones and a higher incidence of osteoporosis and age-related bone loss. The researchers warn that with the deskbound lives that many people lead today, our bones may have become even more brittle than ever before. "We are not challenging our bones with enough loading," says Colin Shaw, "predisposing us to have weaker bones so that, as we age, situations arise where bones are breaking when, previously, they would not have."
... what we get in weaker bones, we get in more refined minds (aka sitting and reading, researching, etc). Now some may laugh at this idea in the modern era, but you have to remember you only have so much time and energy as an organism. It'd be interesting to know whether bones needing lower maintenance/energy has some pro's instead of just cons.
Have gnu, will travel.
Humans regularly lived to their 50s and 60s as far back as the paleolithic. Average life expectancy numbers are misleading because the high rate of infant mortality and death during childhood. A hunter-gatherer who can survive long enough to be a teenager is quite likely to live to old age, but it's getting that far that's the tricky part.
That is not how averages work. Yes, the average age was 20-30 years but that includes lots of children, newborns, and possibly war deaths (depending on which statistics you are looking at). Generally speaking if you lived to puberty then you had a reasonable chance to hit 60+ just like modern humans.
Also consider the introduction and increasing consumption of alcohol. It has significant calcium reducing properties.
Classic nerds vs. geeks. Nerds are happy to be sacks of goo because exercise is not interesting to them. For geeks, everything is an optimization problem - the meatsuit gets no pass.
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Modern human skeletons have shifted quite recently towards lighter—more fragile, if you like—bodies.
Sweet! Maybe we will also start evolving wings and finally be able to fly without manufactured air foils! I for one intend to sit on the couch more and make this happen faster!
If humans could fly, we'd consider it exercise and never do it.
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"pinpoints the origin of weaker bones at the beginning of the Holocene epoch roughly 12,000 years ago, when humans began adopting agriculture". This doesn't have anything to do with tractor farming.
But it does raise a serious issue - they're studying changes that don't necessarily reflect the selective pressures of present-day life.
Think about it: what are the leading causes of death for people in the prime breeding age (15-34)? Car accidents - by a good margin. So isn't this significant selective pressure to beef up the neck against whiplash, the skull against forehead impact, survival during significant blood loss, etc?
#2 is suicide. I don't know how this rate has changed over time or whether the methods modern humans choose for attempts are more effective than would have been chosen in the past. For example, while men commonly turn to firearms, which are a very effective way to commit suicide, women more often turn to prescription medication overdoses as a method, which overwhelmingly fails.
#3 is poisoning. While humans have always been around poisons, the sheer number that we keep in our houses, most of types that we didn't evolve to, suggests that this may be a stronger selective factor now than it was during our agrarian days, perhaps comparable to that when we were hunter-gatherers or worse.
#4 is homicide. We've definitely gotten a lot better at that, a person is far more likely to die from an intentional gunshot wound than a beating or stabbing. Selective pressures: surviving blood loss, mainly. Stronger, thicker bones may help in against low velocity penetrations.
#5 is other injuries. Again, we're not as likely to suffer from, say "crushed by a mastodon" as an injury, but we've developed plenty of new ways to get killed or maimed in our modern lives.
Then it gets more complicated on the basis that the issue isn't just about survival of the individual, but their social group as a whole, so even nonbreeding members can have a major impact...
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