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It seems that life is really good at assembling carbon into extremely complicated molecules (e.g. DNA). Graphene is stronger than any materials currently used by biology. Diamond is harder than any biological materials. Do we know about some inherent difficulty that prevents this? Is there any reason to think that humans will never be able to genetically engineer say, bacteria/fungi/ourselves, to produce diamond, graphene, carbon nanotubes, etc?

I'm looking for specific metabolic hurdles that would make this difficult or impossible. (For example, enzymes/proteins can't do that for this reason, or ATP metabolisms don't have enough energy to form the needed bond.)

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    $\begingroup$ well, life, meaning humans, are capable of producing artificial diamonds, i.e. en.wikipedia.org/wiki/Synthetic_diamond I would suggest you look into energy required for creating diamonds (3000 deg C, 3.5 GPa) versus energy biology is able to apply in biochemical reactions $\endgroup$ – aaaaaa Mar 20 '17 at 4:02
  • $\begingroup$ Possible duplicate of Why do some bad traits evolve, and good ones don't? $\endgroup$ – James Mar 20 '17 at 5:30
  • $\begingroup$ as aaaaaa stated, diamond require high heat/pressure to create. Zoological bodies/tissues can't do that. Also, you should review production techniques for creating graphene and try to imagine how a biological organism could accomplish a similar task $\endgroup$ – theforestecologist Mar 21 '17 at 14:14
  • $\begingroup$ Although your post is interesting, your main question, " Is there any reason to think..." qualifies this question as being primarily opinion-based (i.e., "answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise."). I would suggest editing your question to avoid closure. $\endgroup$ – theforestecologist Mar 21 '17 at 14:17
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Biology does not have too many uses for super hard but brittle materials like a diamond. The hardest biological materials are also very tough as well since they need to form complex shapes for maximum utility. Limpet teeth are the hardest biological material known but are also incredibly strong, stronger than steel, not super brittle like diamond1.

As for graphene, the big problem there is reactivity; graphene is a great substance except it is pure carbon and has a huge surface area. If you put it in a solution full of carbon reactive chemicals, it starts doing weird things, and it has particularly weird interactions with cell membranes. Structurally, it is far more trouble than it is worth in something made of cells2.

You also have to remember that, in evolution, it is generally about "good enough", not perfection. Making a pure carbon structure would be an incredibly costly process in a biological (and thus aqueous) environment.

References:

  1. Extreme strength observed in limpet teeth

  2. Exploring the Interface of Graphene and Biology

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  • $\begingroup$ Good answer, but could I also suggest the problem of breaking it down again. If a biological structure is damaged, or the organism needs to grow, it has to be able to break down its structure - this could be difficult for a substance as stable as graphene or diamond $\endgroup$ – gilleain Mar 20 '17 at 10:42
  • $\begingroup$ I think there are plenty of uses for diamonds. Rodent teeth are composed of a hard, brittle face with a softer, tougher backing structure. The hard face could be replaced with diamond. Grass grows phytoliths which would be a perfect application of even highly brittle diamonds. Composite materials are usually combinations of hard, brittle materials with high tensile strength fibers (e.g. reinforced concrete, epoxy fiberglass). Diamond reinforced by carbon nanotubes would seem to be the ultimate expression of this strategy. $\endgroup$ – hexagon Mar 21 '17 at 0:26
  • $\begingroup$ considering rodents can already chew through concrete with teeth made of a salt composite diamond is not going to gain them a whole lot. and far more costly to make while not necessarily showing better wear resistance.phytoliths are made from silica which is basically free (the plant absorbs some by accident as it tries to dissolve other useful minerals out of soil. daimond would compete for cellulose and sugar for carbon usage. $\endgroup$ – John Mar 21 '17 at 2:28
  • $\begingroup$ diamond by their very structure do not bond well with anything, they are all but useless for composites. $\endgroup$ – John Mar 21 '17 at 2:35
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    $\begingroup$ @gilleain: Breaking down a structure isn't the only solution. Many animals (sharks, for instance) shed worn teeth and grow new ones. Many arthropods shed their carapaces and grow new ones, snakes shed their skin, and (as I am all to well aware of right now) dogs & horses shed their winter coats. $\endgroup$ – jamesqf Mar 21 '17 at 4:12
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Biology is way ahead of us in producing stuff with useful properties. Nanotubes are nothing new, some structures in your body are made out of nanotubes, take e.g. your tooth enamel. The nanotubes there can become depleted of minerals after eating foods containing acids, but they'll refill in about an hour's time. This is why your dentist will tell you to not brush your teeth immediately after eating a meal. Empty nanotubes are easily damaged, they won't be replaced so you'll have permanent mineral loss.

Diamonds crystals have no known use for ling organisms and they are also hard to grow in a biological setting. You have to keep in mind here that humans are used to build structures on a macroscopic scale. Machines that we build will have smallest functional parts that are still enormously large when viewed at the atomic scale. This then means that our machines are prone to degradation due the system accumulating damage at scales that are smaller than the smallest accessible scale.

Biological systems don't have this problem because the relevant machine parts here are at the molecular scale. Damage at smaller scales requires bonds between atoms to be broken which requires very high energies. Also the systems themselves are small enough to intervene at that scale. So, the reason why we want to use diamond (a strong material that doesn't degrade) is not relevant for biological systems.

Here we also need to keep in mind that biological systems are constantly at work to maintain themselves. So, it's not like any machine that we build that only very occasionally will need downtime for maintenance and still we'll take it for granted that it will degrade over time. A biological system will almost immediately fall apart if the internal self maintenance processes were to stop. It's the equilibrium between breakdown and rebuilding that keeps your body in shape. Increasing the demand for rebuilding by exercising will shift the balance such that your body becomes stronger.

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  • $\begingroup$ If hard materials weren't useful for biological organisms, they wouldn't make them. Biological organisms do make hard materials - teeth (as you mentioned), scales, bones, claws, pincers, exoskeletons, bivalve shells, diatom shells, beaks, phytoliths, etc. Diamond is highly resistant to acid, which would prevent cavities. Its hardness would greatly reduce tooth wear in herbivores ingesting phytoliths or digging rodents. Diamond faces on compound eyes would reduce scratching. $\endgroup$ – hexagon Apr 16 '17 at 23:12
  • $\begingroup$ @hexagon Yes, I agree here, but do note that in biology the stuff that is used is also being manufactured at the same time. So, you're bones are constantly being broken down and also build up. For diamonds to be used would require the machinery to make the stuff from diamonds to be there at work too. We tend to think of the building phase as being separate from just having that stuff after it's being build, it's then a static thing. To appreciate that biology is different, you should watch these videos youtube.com/watch?v=SNiiLfB8s0s and youtube.com/watch?v=zkGb12xBKlM $\endgroup$ – Count Iblis Apr 16 '17 at 23:25
  • $\begingroup$ Bones are created that way, yes, but I don't believe that is the case for all hard materials. Exoskeletons are molted. Snail and bivalve shells are shaped to grow indefinitely. I suspect phytoliths never shrink. $\endgroup$ – hexagon Apr 26 '17 at 0:57

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