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This question is based on another question that I asked last year: How to Give an Ordinary Man Vampire Strength

That question was on the basis on one overlooked trait of Bram Stoker's Count Dracula, that he possessed the strength of twenty men. In the only answer I got was this one crucial sample:

A chimp is two to five times stronger than a human per unit weight, but doesn't have the same level of fine motor control.

In other words, while a chimpanzee does have enough strength to be considered "superhuman", it lacks the finer nuances of dexterity needed for the finer things of life, like holding a pencil long enough to write an old-fashioned essay on the meaning of life. That is the price to pay for having denser nerve fibers, but this has left me asking: Is this sort of extra nerve fiber density monolithic among the entire body? Or can certain parts of the body have differences in nerve fiber densities?

In this scenario, the nerve density of a human hand and fingers are the same, but the nerve fibers on the arms are far denser. Is this sort of differentiation possible, much less feasible?

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  • $\begingroup$ What exactly do you mean by “denser nerves?” More nerve endings? More nerves in general? $\endgroup$
    – Topcode
    Dec 31 '21 at 4:25
  • $\begingroup$ @Topcode More like the brain of a corvid songbird in comparison to an ape's brain. $\endgroup$ Dec 31 '21 at 5:28
  • $\begingroup$ /That is the price to pay for having denser nerve fibers/ - is the chimp stronger because it has denser nerve fibers? $\endgroup$
    – Willk
    Dec 31 '21 at 20:13
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The 3 Things are Independent

There are 3 things at play for each muscle:

(1) The power of the muscle. This is controlled by the arrangement of bones, muscles and tendons.

(2) The fine control. This is controlled by the type of motor neurons that connect to the muscle.

(3) The sensitivity. This is controlled by the density of sensory neurons that connect to or nearby the muscle.

You can in principle have a powerful and highly sensitive muscle with fine motor control, by just having more or better neurons. For example the jaw is very powerful and has fine control. Ie I can chew through a bone and stop my jaw just in time to not break my own teeth against each other.

The reason chimps have powerful but clumsy muscles is the evolutionary tradeoff. It is biologically expensive to have sensitive and dextrous muscles, since you need a bigger brain to coordinate them, and the brain uses a lot of energy. Better to have powerful but clumsy arms, with dextrous fingers, and sensitive fingertips.

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Or can certain parts of the body have differences in nerve fiber densities?

It is totally possible, and it already happens in humans, too.

For a notorious example, look at human genitalia: the nervous system forms before the sexual diversification of the embryo, meaning that the number of nerves is the same between the sexes. Then, when the sexual diversification happens and the anatomy follows, we get that the same number of nerves which in a male become located in the penis, in a female become concentrated in the penis anatomical homologous, the clitoris.

Considering the difference in size between the two, the clitoris has a much higher nerve density than the penis, which also accounts for its higher sensitivity.

Same difference in nervous density happens with tactile sensitivity: our hands are way more sensitive than our backs, due to the higher concentration of nervous termination, as it is depicted in the homunculus mapper

enter image description here

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  • $\begingroup$ So if the nerves on the arms are denser than on the fingers, would that guarantee both strength AND dexterity? $\endgroup$ Dec 31 '21 at 5:29
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    $\begingroup$ I think the above illustration is missing a few parts. Of course, enlargement of these parts could be inappropriate for WB, but for completeness you could edit them in. Stylized.. $\endgroup$
    – Goodies
    Dec 31 '21 at 15:24
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    $\begingroup$ @JohnWDailey Higher nerve density does not lead to dexterity. For example the genitals are more sensitive than the hands but it is still easier to thread a needle with the fingers than the genitals. $\endgroup$
    – Daron
    Dec 31 '21 at 15:51
  • $\begingroup$ I imagine high nerve density is required to make proper use of fine motor control. But they are still separate things. $\endgroup$
    – Daron
    Dec 31 '21 at 15:52
  • $\begingroup$ Upvoted because Dutch promised to use the homunculous as his new icon. $\endgroup$
    – Willk
    Dec 31 '21 at 20:15

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