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Surprised that this totally blows past the chemical reasons why not. There's an excellent answer by shigeta on the Biology Stack Exchange[1] to this very quest

Surprised that this totally blows past the chemical reasons why not. There's an excellent answer by shigeta on the Biology Stack Exchange[1] to this very question. His major answers are that electrical conductivity is likely to be a huge problem for the nervous system, and that iron and aluminum readily oxidize (aka rust). Iron oxidization is useful in hemoglobin but would be problematic in your bones, and while a body could be designed with conductivity in mind, it would at minimum also take a reworking the nervous system. 1: https://biology.stackexchange.com/q/9419/4101 https://biology.stackexchange.com/q/9419/4101

jstanley 9y ago
If conductive bones are problematic, why do Titanium pins etc. not cause problems?
- Amorymeltzer 9y ago
  For one, the pins are small and hopefully don't touch nerves. More to the point, Titanium: — Is nontoxic. — Is biocompatible, and can semi-integrate into bones, a process called osseointegration[1], which makes for much better implants. — Isn't ferromagnetic, so you can use MRI to examine and maintain implants safely. — Is less conductive than many other metals. 1: https://en.wikipedia.org/wiki/Osseointegration https://en.wikipedia.org/wiki/Osseointegration
  - epmaybe 9y ago
    As an aside, there was a professor of mine in college that had a startup to apply an electric current through some rods and pins to stimulate osteoblast formation and therefore better osseointegration.
gilleain 9y ago
Another problem is breaking/remaking these metal bones. Biomineral structures can be reformed - bones break mechanically, and have to be repaired. While biomineralization is mentioned, I'm not sure how easy it would be to 'digest' pure metal in order to repair it. Also, related : https://biology.stackexchange.com/questions/60780/how-to-form-biological-metallic-tissue https://biology.stackexchange.com/questions/60780/how-to-for...
- tootie 9y ago
  He talked about that in the article. His point being that metal bones would be effectively indestructible for typical loads placed on them by organisms and if they ever received damage, they would bend instead of break.
  - gilleain 9y ago
    Ok, sure, but later on the question is : "So it seems that there are no fundamental reasons why animals could not evolve a metal skeleton" The main reason is that most multicellular organisms (especially vertebrates) go through developmental stages where they grow in size. Mineral bones can be grown like this, while metal ones probably could not.
    - Momquist 9y ago
      How about a change in diet only when reaching mature size (the rock eating suggested in the article)? Doesn't seem too farfetched, and I think it would allow for growth when still developing.
  - jsmthrowaway 9y ago
    Is that better? Imagine a bent leg. It seems like one would want it to break and heal, no?
    - fjsolwmv 9y ago
      A big break pokes a big infected hole in muscle and skin
matt4077 9y ago
I'm not sure if conductivity matters. Bodily fluids are also conductive, yet don't seem to interfere. More importantly, neurons use ion gradients across their membranes to conduct signals. It's not electrons flowing along, as it is for wires. While the magnetic field created by thousands of neurons firing in concert can be picked up using wires (EEG, ECG), and neurons can be induced to fire with electric shocks, I actually doubt anything would happen if you were to connect two neurons by wire. At the very least, the wires would need to have contact with the axons (neuron terminals). A neuron can be a meter long, but it is isolated by a fatty membrane along its body.
- fjsolwmv 9y ago
  Wouldn't a conductor interfere with the in channels, by moving electrons and thereby cancelling the gradient?
nitwit005 9y ago
Isn't the temperature of the chemistry the issue? Your body can't heat up to forge temperatures without catching fire.
- neolefty 9y ago
  The article addresses that, albeit with some hand-waving: > The activation energies for oxidation and reduction of iron are of the order of 30-60KJ/mole, comparable to the figure of 57KJ/mole for ATP, a molecule which is commonly used for delivering energy around our bodies. We normally make iron from its ore at very high temperatures, because the rate-limiting process is diffusion in the solid state. But the body makes materials in a very different way, from the bottom up, atom by atom, molecule by molecule. And of course the fact is that you are already oxidizing and reducing iron inside your body all the time.
x2398dh1 9y ago
What you pointed out is a very astute answer, but comes from a creationist perspective rather than an evolutionary perspective. His main answer is: > Firstly, fully reduced (oxidation state 0) metal has a high energetic cost to create in reduced form. Basically, it takes a ton of energy to make steel. We are literally burning gigagallons of over a billions years worth of pressurized organic matter to have made all of the steel we have made in the past century and a half or so. We could make a super inaccurate but somewhat plausible estimation that we have used something like 150 million years worth of the entire earth's lifeforms at the time's dead bodies and converted that into 150 years worth of steel. So if my orders of magnitude are correct...it would be something like a million times more difficult energy-wise for an organisms to create steel from scratch than calcium-based hardened material. That's assuming we have burned through 15% of a billion years worth of oil from bacteria, that 100% of the bacteria converted into oil and then converted directly into steel, and that there was only a billion years of bacteria to oil creation. I am sure these numbers are off, but maybe that means it's only 100,000 times or 10 million times more difficult for organisms to make steel rather than bones.
- jotm 9y ago
  Well that's interesting, it seems we've got the next few centuries to start colonizing the solar system, or we're going to go extinct at this rate of usage... Who was it that made the theory, a next civilization may never happen because we used up all the easily available resources...
- Dylan16807 9y ago
  You are vastly overestimating the efficiency of turning life into oil, and vastly overestimating how much has gone into steel. The article even addresses the energy needed to reduce iron, and it's not that much. The high number of 60kJ/mole/reduction comes out at about 500 food calories per kg to reduce twice. Industrial molten iron production is only around 5000 food calories per kg. So it's really no big deal to produce a few kilograms per lifetime. (Mixing in other elements to get steel is a minor cost per kg.)
- fjsolwmv 9y ago
  How is it Creationist? Creationism is just a metaphor for evolution plus a fictional goal of evolving toward specific human form.

jstanley 9y ago

If conductive bones are problematic, why do Titanium pins etc. not cause problems?

Amorymeltzer 9y ago
For one, the pins are small and hopefully don't touch nerves. More to the point, Titanium: — Is nontoxic. — Is biocompatible, and can semi-integrate into bones, a process called osseointegration[1], which makes for much better implants. — Isn't ferromagnetic, so you can use MRI to examine and maintain implants safely. — Is less conductive than many other metals. 1: https://en.wikipedia.org/wiki/Osseointegration https://en.wikipedia.org/wiki/Osseointegration
- epmaybe 9y ago
  As an aside, there was a professor of mine in college that had a startup to apply an electric current through some rods and pins to stimulate osteoblast formation and therefore better osseointegration.

gilleain 9y ago

Another problem is breaking/remaking these metal bones. Biomineral structures can be reformed - bones break mechanically, and have to be repaired. While biomineralization is mentioned, I'm not sure how easy it would be to 'digest' pure metal in order to repair it. Also, related : https://biology.stackexchange.com/questions/60780/how-to-form-biological-metallic-tissue https://biology.stackexchange.com/questions/60780/how-to-for...

tootie 9y ago
He talked about that in the article. His point being that metal bones would be effectively indestructible for typical loads placed on them by organisms and if they ever received damage, they would bend instead of break.
- gilleain 9y ago
  Ok, sure, but later on the question is : "So it seems that there are no fundamental reasons why animals could not evolve a metal skeleton" The main reason is that most multicellular organisms (especially vertebrates) go through developmental stages where they grow in size. Mineral bones can be grown like this, while metal ones probably could not.
  - Momquist 9y ago
    How about a change in diet only when reaching mature size (the rock eating suggested in the article)? Doesn't seem too farfetched, and I think it would allow for growth when still developing.
- jsmthrowaway 9y ago
  Is that better? Imagine a bent leg. It seems like one would want it to break and heal, no?
  - fjsolwmv 9y ago
    A big break pokes a big infected hole in muscle and skin

matt4077 9y ago

I'm not sure if conductivity matters. Bodily fluids are also conductive, yet don't seem to interfere. More importantly, neurons use ion gradients across their membranes to conduct signals. It's not electrons flowing along, as it is for wires. While the magnetic field created by thousands of neurons firing in concert can be picked up using wires (EEG, ECG), and neurons can be induced to fire with electric shocks, I actually doubt anything would happen if you were to connect two neurons by wire. At the very least, the wires would need to have contact with the axons (neuron terminals). A neuron can be a meter long, but it is isolated by a fatty membrane along its body.

fjsolwmv 9y ago
Wouldn't a conductor interfere with the in channels, by moving electrons and thereby cancelling the gradient?

nitwit005 9y ago

Isn't the temperature of the chemistry the issue? Your body can't heat up to forge temperatures without catching fire.

neolefty 9y ago
The article addresses that, albeit with some hand-waving: > The activation energies for oxidation and reduction of iron are of the order of 30-60KJ/mole, comparable to the figure of 57KJ/mole for ATP, a molecule which is commonly used for delivering energy around our bodies. We normally make iron from its ore at very high temperatures, because the rate-limiting process is diffusion in the solid state. But the body makes materials in a very different way, from the bottom up, atom by atom, molecule by molecule. And of course the fact is that you are already oxidizing and reducing iron inside your body all the time.

x2398dh1 9y ago

What you pointed out is a very astute answer, but comes from a creationist perspective rather than an evolutionary perspective. His main answer is: > Firstly, fully reduced (oxidation state 0) metal has a high energetic cost to create in reduced form. Basically, it takes a ton of energy to make steel. We are literally burning gigagallons of over a billions years worth of pressurized organic matter to have made all of the steel we have made in the past century and a half or so. We could make a super inaccurate but somewhat plausible estimation that we have used something like 150 million years worth of the entire earth's lifeforms at the time's dead bodies and converted that into 150 years worth of steel. So if my orders of magnitude are correct...it would be something like a million times more difficult energy-wise for an organisms to create steel from scratch than calcium-based hardened material. That's assuming we have burned through 15% of a billion years worth of oil from bacteria, that 100% of the bacteria converted into oil and then converted directly into steel, and that there was only a billion years of bacteria to oil creation. I am sure these numbers are off, but maybe that means it's only 100,000 times or 10 million times more difficult for organisms to make steel rather than bones.

jotm 9y ago
Well that's interesting, it seems we've got the next few centuries to start colonizing the solar system, or we're going to go extinct at this rate of usage... Who was it that made the theory, a next civilization may never happen because we used up all the easily available resources...
Dylan16807 9y ago
You are vastly overestimating the efficiency of turning life into oil, and vastly overestimating how much has gone into steel. The article even addresses the energy needed to reduce iron, and it's not that much. The high number of 60kJ/mole/reduction comes out at about 500 food calories per kg to reduce twice. Industrial molten iron production is only around 5000 food calories per kg. So it's really no big deal to produce a few kilograms per lifetime. (Mixing in other elements to get steel is a minor cost per kg.)
fjsolwmv 9y ago
How is it Creationist? Creationism is just a metaphor for evolution plus a fictional goal of evolving toward specific human form.