In this question, we were provided a look at what would happen if a human-like species was capable of moving faster than the speed of sound. The consequences of such a modification seem rather disastrous, so I'd like to propose something different: modifying the human nervous system.

If humans, or at least a subset of humans, had some quality that increases their ability to process and react to external stimuli (e.g., see it, know what it is, and react to it), covering the brain, muscles, sensory organs, and nervous system, how would general life be different for the altered human? At what point would the difference between a regular human and this altered human be ultimately noticeable and beneficial: 5% better reaction times, 10%, 30%, more? Would the body need to be altered in any further way to support this mutation?

Bonus points if you can provide a purely biological method to support this mutation.

To head off anyone pointing out another related question: This question remarks on a species with a much-accelerated nervous system. Note that I am not looking to make a human have a noticeable lag time between thought process and physical activity, as the accepted answer concludes, but rather to give a human a sufficient edge in hand-to-hand combat to be able to easily predict an opponent, to have a better chance to dodge a bullet, and otherwise have extraordinary ability.

  • $\begingroup$ Can't think of anything biological that wouldn't require radically non-human DNA. Various ideas with cybertech and nanotech...and of course non-science based such as the Jedi and Sith who have human biology, but also prescience and so start reacting before the event happens. $\endgroup$
    – Zan Lynx
    Feb 16, 2015 at 2:05

4 Answers 4


So, faster reaction times? Like Miles Teg in the later Dune novels?

Without techno-magic? That's going to be tough.

To speed up a nervous system you'd have to do one of two things:

  • Make each neuron faster
  • Make the length of the neuron perception->computation->reaction chain shorter.

Making neurons faster

Neurons, especially outside your brain, are pretty slow, as this video beautifully demonstrates. The speed of transmission depends on the quality of the cabling. For fast long distance communication with distant parts of the body the Nervous system has its axonic cabling covered with a myelin sheath, which speeds up nerve impulses by a factor of 10, via saltatory conduction. Within the computational centers in the brain where the neuron-body to neuron-body distances are much shorter, myelinization is less of an issue, and more lossy communication can occur.

It is tempting to think that after 400 million years of multicellular evolution, neurons are about as fast as they can get. That's actually not the case. Evolution optimized for the best combination of speed and low energy consumption it could, and if you look at the actual process, it seems a bit of a kludge.

It's not inconceivable that if we were to redesign a human body under our no-energy-constraints current situation, we could get significantly faster conduction, bounded upward by the electromagnetic propagation speed of $c$. Significant upgrades could be achieved at the neurotransmitter bottleneck, for instance. Of course, we don't need a million-fold speed increase to have merely faster reaction times, so relatively minor tweaks could work. Some of them could even evolve biologically as we move away from the food-being-an-issue as a species, but genetic engineering is a faster way to get there.

Making loops shorter

The other way to make reaction times faster is to cut down the number of layers of communication and processing between sensory activation and action. To act real-time, a perception-to-action loop can be about 100 neurons long, with the slow axonic Na+ K+ based electric conduction, the even more inefficient axon terminals where neurotrasmitters are sloshed around. Ugh. Let's try to chop some of that off.

A real-world example is the spine-based instinctual reflex reaction (such as the command directing your hand to move away from a hot surface). Imagine you were able to program a reflex reaction to Kalashnikov rifles, or to people wearing the wrong kind of uniform, of whatever fits your criteria of enemy. No thought required, just a pre-recorded action shortcut. It is suspected that grandmaster samurai swordsmen, for instance, through decades of practice, were able to enter such a reflexive state at the start of 1-on-1 combat, acting without thought or hesitation.

If you're willing to add some cyber components on top, you can have all sorts of fancy sensors, computing substrata and then action directed by cartilage, muscle and bone upgrades to allow for high-speed actions far beyond the capabilities of mere flesh-humans.

  • 1
    $\begingroup$ From what I remember from 9th grade bio, the major limiting factor in reaction time is not the time it takes for the electrical signal to propagate along the length of a nerve, but the time it takes the chemical neurotransmitters to diffuse across the space between neurons. If you could transmit a nerve impulse electrically from one neuron to the next, then you could cut down your reaction times by more than half. (Someone please fact-check me here: I'm an engineer, not a doctor!) $\endgroup$ Feb 15, 2015 at 19:24
  • 2
    $\begingroup$ @2012rcampion, Yup, that's what i said "with the slow axonic Na+ K+ based electric conduction, the even more inefficient axon terminals where neurotransmitters are sloshed around" $\endgroup$ Feb 15, 2015 at 20:29
  • $\begingroup$ Whoops, I didn't quite catch that on the first read... I would add some conjunctions to that sentence to make it easier to parse. $\endgroup$ Feb 16, 2015 at 0:55
  • $\begingroup$ Cybernetic ganglia, nice +1 $\endgroup$
    – Samuel
    Feb 16, 2015 at 1:13
  • $\begingroup$ Your link to "seems a bit of a kludge." seems to be broken, do you have any replacements because it sounded like a good video to watch $\endgroup$
    – Ferrybig
    Mar 28, 2017 at 16:39

The Problem:

In order to produce a significant advantage in combat as a result of faster reaction times, it is necessary to either operate inside of the opponent's decision/action loop (i.e achieve tactical surprise), thus requiring the opponent to think about reacting to a situation that you have already thought about, or to significantly decrease the opponent's physiological reaction time. Cutting a few percent off the reaction time won't be sufficient, you'd need to have a quite significant reduction in reaction time to observe any significant combat advantage. We're looking at about a 15-20% reduction in reaction time at minimum.

Genegineering Solution:

If you had no limits as to the sophistication of your genetic engineering other than the practical limits of the materials you're working with, have a look at my answer to the second question referenced. To summarise, neural conduction could be accelerated by precipitating metals (or graphene) and neural connections could be accelerated by using mechanical rather than neurotransmitter-mediated gates.

It would be rather more difficult, but not impossible, to dramatically improve the speed of muscle contraction, but by dramatically reducing reaction times at least, it would be possible for a human so enhanced to out-think and out-react any unenhanced human, with or without higher muscle contraction speeds.

Human eyes are not the fastest eyes in the animal kingdom either, so it would not be too difficult to make the necessary changes to speed them up either.

Given all these advantages engineered into a single individual, including faster musculature, it would be possible to see bullets in flight and to have a chance to dodge or deflect them, though the chances would probably be on the order of an unenhanced human dodging or deflecting an arrow from a bow - very difficult, but not impossible at sufficient range.

If it came to combat of any sort between enhanced and unenhanced humans, the outcome would be heavily skewed in favour of the enhanced human, regardless of the training of the unenhanced human and any lack of training of the enhanced human. Unenhanced humans would have to rely on attacking unobserved or using heavy weaponry to have any certainty of defeating such an opponent.

However, this would come with certain disadvantages.

Unless the genetic engineering was done very carefully and cleverly, such a 'human' would not actually be human in anything but appearance. The most likely outcome is that they would not be sufficiently genetically human to be able to successfully interbreed with unenhanced humans, and even in the unlikely event that they could, their offspring would be far closer to the unenhanced parent than the enhanced parent.

Secondly, during pregnancy and childhood, if metal precipitation was used to accelerate axonal pulse transmission, it would be necessary to supplement the diet with the metal in question, probably silver due to its low resistance, as the levels of metal required would not naturally occur in an unenhanced human's diet. However, graphene precipitation would not have this drawback.

Thirdly, as speed increases, so too do metabolic costs. Enhanced humans would have a higher basal metabolism simply due to their more active neurology, and acting more rapidly would have a similarly higher metabolic cost. Put simply, these people would have to regularly eat the sorts of meals that for the most part only morbidly obese unenhanced humans would choose to eat.

Fourthly, were such enhanced humans engineered, and they constituted a separate species as is most likely (and even if not), there would be a strong impetus for active competition between the groups to occur, as slower or not, unenhanced humans are still smart and quick enough to see how they are outclassed. This could quite quickly descend into a war between the enhanced minority and the unenhanced majority a-la the Marvel X-Men universe.

Fifthly, enhanced humans would not obtain the same enjoyment from the movies that unenhanced humans watch without software enhancement: since we are talking about enhanced humans having faster eyes, this would increase the fusion frequency. Our movies are typically shot at around 25 Frames Per Second (FPS). However, this would be below the fusion frequency of enhanced humans, who would see a series of static images. Enhanced humans may have a fusion frequency requiring frame rates of 50-100 FPS or even more. This may be able to be compensated for by inter-frame interpolation, but would require a lot of computing power.

Evolutionary Solution:

From an evolutionary perspective, it would be very difficult to evolve these adaptations, even in the presence of an evolutionary stimulus. Sodium-gate neurotransmission is so heavily tied into the viability of organisms that any mutations which affect this would be highly likely to result in a non- or less- viable organism. Evolution is far more likely to produce iterative improvements on the current theme, not a wholesale cut and replace solution such as the genegineered solution above. Creatures have been evolving side-by-side for millions of years in an attempt to out-react one another, and the current neurology is the best that has occurred naturally. Any significant improvements would have to come as a series of individually viable steps, each of which provided some advantage, whereas geneginering can implement a whole lot of steps at once without requiring incremental advantage.

Evolution is limited in that in a solution space with multiple uneven peaks, solutions will tend to move up the current gradient to the top of the closest peak, and to jump across to an adjacent, higher peak is effectively impossible, as this would involve a reduction in fitness before there could be an effective improvement in fitness.

This means that when starting from a different evolutionary point, it might be quite easy to evolve a faster system such as this, but we can't get there from here, since we can't go backwards.

Hybrid solution:

From a certain point of view, genegineering is an evolutionarily valid solution to this problem: your species, (humans in this instance) have evolved high intelligence, and have used that to accumulate a cultural store of knowledge which can be used to develop techniques of genetic engineering, hence it can be said that humans are in the process of evolving the ability to produce game-changing advantages in future generations in a very short timespan. By evolving high intelligence, we are in the process of gaining the ability to potentially jump to an adjacent, higher peak of fitness without the necessity to suffer generations of lower fitness first. Why say that evolution always has to be unintelligent? We're becoming quite capable of our own intelligent design, no prehistoric creator needed.

  • $\begingroup$ Fascinating. Thanks. But I notice you approach this from an engineering perspective. Would there be a possibility that such a mutation could occur naturally (not necessarily the metal precipitate)? $\endgroup$
    – Frostfyre
    Feb 15, 2015 at 23:33
  • $\begingroup$ Have a look at my edits. $\endgroup$
    – Monty Wild
    Feb 16, 2015 at 0:18
  • $\begingroup$ Well, my setting was intended to be modern day Earth, so not much in the field of bioengineering. Still, my character works for a non-Earth company and so need not be entirely human, I suppose. $\endgroup$
    – Frostfyre
    Feb 16, 2015 at 1:59

Selective breeding would do it.

There is more variation in human reaction times than most people expect. I happen to have unusually fast reactions. Very handy for a a gunsel, or twitch video gaming.

Years ago in drivers ed, there was a reaction test. My teacher accused me of cheating because "no-one" could be that fast -- of course, he could not think of any way that cheating was even possible (nor can I). He had been teaching drivers ed for about 30 years, giving the same test to everyone and no-one was ever close to my reaction speed.

Check out the reaction time dollar bill test video. The person attempting to catch the dollar bill, should have their fingers near the bottom of the bill, even then few people can catch the bill. When I was 20, I could catch the bill about the middle of the bill. I tried this on my 70 year old mother a few years ago, she could still catch the bill. Genetics play a part.

My sister, however has extra slow reaction speeds, almost 3 times as slow as me.

Given the natural variation, with selective breeding alone (either eugenics, or making gunfighting very common would do it) you could get a 50% speedup in reaction times (a bit less improvement than I had at age 20).

Some CNS stimulants also speed up reaction times, but caffeine alone does not make you more than a small amount faster.


I think the best thing to do is in play at the body in certain joints in spots on the body with reaction sensors that electrically heat the nerves to allow quicker movement and stimulate blood flow. If your eyes could see something bad was about to happen then the implants heat the right nerves in the right muscles in the body to move quicker.

  • $\begingroup$ This wouldnt work. The OP seems to focus on a biological/evolutional method. Nerves dont work on heat. If nerves did work on heat the implant would need to receive a signal from the nerves before it works. Nerves work along the entire length of the body, the joints would only accelerate a tiny portion of the nerve signal. Muscles are positioned around joints not in/on them. Bloodflow is already stimulated at its maximum during excercise especially considering muscle contraction squeezes the veins tighter hampering Bloodflow and pumping some of it out. $\endgroup$
    – Demigan
    Apr 25, 2018 at 6:47

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