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Bone is an organ with multiple functions beyond structural support. It creates a reservoir for calcium and phosphate homeostasis and of course contains bone mar
by Gatsky 9y ago
Bone is an organ with multiple functions beyond structural support. It creates a reservoir for calcium and phosphate homeostasis and of course contains bone marrow. It also has attachments for muscles and connective tissue, and adapts to environmental conditions (eg see a tennis player's forearm). A titanium bone could do none of these things. The question should really be why are bones not reinforced with metal or metal composites. In general if greater strength is needed it can be achieved with thicker bone, which has a far lower evolutionary barrier than eg metal composite bones. Additionally, the material properties of the whole biomechanical apparatus need to be considered. A super strong skinny thigh bone isn't much good if the area available for ligamentous attachment is so small that the tendons keep tearing. Most injuries involve connective tissue and muscle rather than bone.
- agumonkey 9y agoGood point, although there could be some strands of metallica alloy through the bone matrix to reinforce it, breaking your bones is so rare for most people, it's no surprise nature spent budget on other places.
- matt4077 9y agoIt's sometimes underestimated at what level of detail evolution operates. Consider this: there must have been quite a lot of prehistoric humans who died, or otherwise suffered reproductive failure, because they lacked eyebrows. Breaking major bones, especially in times before modern medicine, was without a doubt a life-threatening event. And considering the prevalence of fractures today, with our largely sedentary lives, it must have happened fairly often
- masklinn 9y ago> Breaking major bones, especially in times before modern medicine, was without a doubt a life-threatening event. And considering the prevalence of fractures today, with our largely sedentary lives, it must have happened fairly often They're not that prevalent, and they may not have been more prevalent in the past, sedentary life likely contributes to some form of osteoporosis by providing less continuous stress and it adds "extreme" sports as discrete high-risk events. And of course just because it's life threatening does not mean it's going to be weeded out, selection is an important part of evolution.
- toasterlovin 9y agoI think many people greatly underestimate the degree to which the body is an adaptive system and, specifically, the degree to which a sedentary lifestyle interacts poorly with this aspect of our bodies. The thing that brought this into full relief for me was the story of Brian Jones, a member of the Starting Strength community. He fell off of a roof and shattered both legs. Doctor told him he would never walk again, etc., etc. But he did. And then he start lifting weights. Of course, his body adapted to the increasing load he was placing on it. Specifically, his body responded by growing muscle and making his bones more dense. His bones got so dense that the metal pins which were inserted into his leg bones after his accident started getting pushed out into the surrounding flesh and he had to have surgery to remove them (links to his story below). I would bet good money that the majority of bone breaks (excluding things like car crashes and obvious stupidity), even in children, are a result of our largely sedentary lifestyles interacting with our body's evolved tendency to not engage in metabolically expensive activity like growing muscle and denser bone unless it receives signals indicating that they are actually demanded by our environment. Brian Jones' story: Video form: https://startingstrength.com/resources/forum/articles-and-platform-videos/40189-barbell-training-rehab-brian-jones-story.html https://startingstrength.com/resources/forum/articles-and-pl... Written form: https://startingstrength.com/article/barbell_training_as_rehab https://startingstrength.com/article/barbell_training_as_reh...
- fjsolwmv 9y agoBrian Jones is an extreme person. Prehistoric man couldn't replicate his level of executive
- toasterlovin 9y agoOn the contrary: that Brian Jones (along with many other men) possesses a body which is capable of getting strong enough to lift 600+ lbs off the floor is pretty strong evidence that our evolutionary past often required humans to get pretty damned strong.
- 9y ago
- toasterlovin 9y ago> There must have been quite a lot of prehistoric humans who died, or otherwise suffered reproductive failure, because they lacked eyebrows A bit pedantic, but: there doesn't need to be a direct line between a morphological feature, like eyebrows, and death and/or inability to reproduce. Evolution is a statistical process that operates over an entire population of organisms. So, a feature like eyebrows can evolve even if they have a relatively minor impact on organisms with eyebrows, like, say, by making them 3% better at hunting or whatever. Because if you have a population of thousands or millions of organisms, that 3% hunting advantage will make a difference.
- falcor84 9y agoI'd argue that being 3% worse at hunting than one's competitors can definitely become a reproductive failure.
- toasterlovin 9y agoAgree, but only at the margins. That one thing, in and of itself isn't a reproductive failure. But over a population with varying levels of, say, hunting proficiency, there will be enough people who are already not very good at hunting and a gene that makes you 3% worse will result in them having less or no children.
- lurquer 9y agoIs there a correlation between reproduction and eyebrows? Seems like a simple thing to study. I doubt anyone has. (And, I doubt anyone will.) It's easier to simply conjure up stories about how eyebrows must have had some beneficial effect and then hand-wave while muttering 'millions and millions.' Given the assumed population levels, the timescales involved, and the minuscule statistical effect of something like eyebrow-ness on survival, I expect 'survival of the fittest' had nothing to do with eyebrows. Rather, it's just a random bit of 'noise' in our DNA.
- toasterlovin 9y ago
- agumonkey 9y agoOh it surely was a life threatening event, but it was solved long before humans were upright. After that it was mostly tweaking. About sedentary lives, I'm fairly convinced that nomadism made for stronger everything, bones, tendons, muscles (coordination too) so their lifestyle (granted you're not living near cliffs and have enough food) didn't increase the % of fracture.
- stcredzero 9y agoIt's sometimes underestimated at what level of detail evolution operates. Of course human minds would tend to underestimate this. Evolution harnesses the parallelism inherent in reality and atoms. Natural selection operates at all levels of detail at once.
- corey_moncure 9y agoNot to mention the role of bone in blood cell synthesis! The bone is a fascinating organ and sadly misunderstood by most people. They are, essentially, living rocks. Our bones are innervated, full of living cells, and constantly engaging in a chemical equilibrium with the body on CaPO4 as you point out. Furthermore, the bone needs to grow along with the creature. It has to be soft enough to accommodate childbirth but allow growth and hardening as the organism matures. The process by which this occurs in natural bone is complex and remarkable. Metal bones can't do any of this stuff.
- deleted 9y ago[deleted]
- homero 9y agoIt's also where white blood cells are made. Marrow is most of the job of a bone.
- jcoffland 9y ago> Marrow is most of the job of a bone. Holding our bodies erect is a pretty important job too.
- magice 9y agoExtra functions of the bones cannot explain fully his question. If it is possible to for the body to synthesize whatever material, it can create a frame for the bones, then wrap that frame in bio-active layers. Basically, a skeleton for the skeleton. Given the intricacies of other body organs (think the sizes and complexity of the eyes, says), such is not too hard of the task. In fact, this probably answers all other concerns raised here. Corrosion and electric-conductive? A bio-compatible wrap (similar to enameled steel) solves that. Grinding between different bones? The ends of the bone can be built out of different material than the fragile length. Furthermore, none of these concerns matter for, says, horns, especially the tips. Evolutionary speaking, it makes complete sense for animal to evolve steel-tipped horns: these steel parts hurt no one but their enemies. (also note, carbon fiber avoids a lot of these bio compatibility issues). In other words, animal kingdom did not have metal parts because synthesis is impossible, rather than because of disadvantages of metals per se.
- jcoffland 9y ago> Evolutionary speaking, it makes complete sense for animal to evolve steel-tipped horns: these steel parts hurt no one but their enemies. Lightning might be an important consideration here. An animal's chances of getting zapped would go up significantly if they were waving around metallic horns in a storm.
- bdamm 9y agoGiven that you're only talking about centimeters of metal at best, which in a thunderstorm could be covered in water anyway, and still need to interface to other tissues to achieve conductivity to the earth, then would the animal's chances of getting zapped go up significantly?
- WalterBright 9y agoReminds me of The 6 Million Dollar Man. His super strength bionic limbs would have just torn the rest of his body apart. Strength has to be in balance with the rest of the body.
- solotronics 9y agocomposite bones with kevlar skin and electromechanical muscles?
- WalterBright 9y agoPut a much stronger engine in your car, and you'll also need to upgrade the brakes, suspension, frame, transmission, driveline, tires, etc. Nothing like dropping the clutch on your new 800 hp motor and having the rear axles snap. Or have the flywheel disintegrate and saw through the bell housing and your feet.
- TheSpiceIsLife 9y ago> The question should really be why are bones not reinforced with metal or metal composites. They are! Calcium is a metal.
- jaggederest 9y agoI think what people mean when they say "reinforced with metal" is "reinforced with substances in metallic form". From that point of charity we can start to say things like "Organic environments cause corrosion in commonly-available pure metals", or "Pure metals can be toxic to animal cells in large amounts".