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Disclaimer: By human-like, I am referring mostly to limb proportions similar to ours.

Would it be reasonable for the average member of a bipedal species with proportions similar to those of humans to be stronger than the average chimpanzee?

The species I am working on in particular is a semi-arboreal species that reentered the forest after evolving efficient bipedal walking. Unlike chimpanzees, the legs are quite long as the legs of humans are. The average height of this species is about 196 centimeters, and the individuals are rather lean with a body fat content of around 12%. The diet of this species contains many energy rich fruits and some meat with other foods such as eggs when the opportunity arises. Currently, I am thinking of a catlike build for individuals of this species, and by this I mean increased flexibility and the ability to react very quickly.

Some things in particular I am wondering about are:

  • If the bones would need to be more dense
  • If tool use would be hindered
  • An approximate weight (would this species be very heavy or light?)
  • If this would take away from intelligence
  • Would endurance be decreased
  • Around what weight could be lifted
  • Would this species be able to react quickly
  • Would the jump height be very high

During my research on the comparative musculature of humans and chimpanzees, I have found claims that involve the chimpanzees having fewer larger muscles and humans having more small muscles. I have had trouble with considering how this would work on a spindly human frame.

Overall, I am wondering what limitations or possibilities there are if this was applied to a human frame. I do not at all expect an exact answer.

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    $\begingroup$ Aren't chimpanzees relatively humanlike to begin with? $\endgroup$ – sphennings Feb 14 '18 at 23:19
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    $\begingroup$ They are. I changed the question to clarify that I meant human-like by body proportion. $\endgroup$ – Cas Feb 14 '18 at 23:26
  • $\begingroup$ Have you researched gorilla anatomy as well? $\endgroup$ – Renan Feb 15 '18 at 0:12
  • $\begingroup$ @Renan I have, but I chose chimpanzees because they are even more closely related to humans than gorillas. Also, gorillas have quite heavy frames and do not spend as much time in trees as chimpanzees. While researching gorillas, I did find some very interesting information on primate musculature and bone structure. $\endgroup$ – Cas Feb 15 '18 at 0:52
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    $\begingroup$ humans are already one of the best jumpers for our size, being bipedal makes for very good jumping ability. you might want to look in to ardipithecus and some of the recent work on early hominids, chimps might have evolved from a bipedal ancestor. ardipithecus is a better designed climber than humans but still bipedal. $\endgroup$ – John Feb 15 '18 at 7:09
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A recent study I read here states that the reason chimpanzees are comparatively stronger than humans is because their muscles sacrifice control for efficiency. I don't know if the whole fewer but larger muscles element is relevant to this but it would make sense. If you replaced human musculature with equivalent chimpanzee musculature, your questions would have the following answers:

  • Greater bone density isn't a necessity but would be a benefit.
  • Like I said, chimpanzee musculature would sacrifice control for power.
  • The difference in weight would probably be negligible without denser bones.
  • I have no idea what role muscle plays in the brain, but I'm guessing intelligence would be about the same.
  • Humans are actually among the most endurant animals in the world and replacing our muscle structure with that of a chimpanzee would definitely reduce that endurance.
  • The World Record for most weight lifted by a human goes to Paul Anderson when he lifted 2.85 tonnes with a back lift. Chimpanzees are supposedly at least twice as strong per-weight as humans so, while your species doesn't sound like it could produce a Paul Anderson, the possibilities are incredible, especially in fist fights.
  • Likely, since this is more down to the capacity of the nerves than that of the muscles.
  • They would definitely be good jumpers. In fact, I would argue that jumping should be a very normal way of getting into trees.

One more thing, for an arboreal species, shorter is actually better. Why do you think chimps are half the size of humans?

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    $\begingroup$ keep in mind the shape of the torso and limbs is a factor, chimps are stronger in some ways and poorer in others, a human can beat a gorilla in a dead lift just becasue our anatomy is better for lifting things over our head. likewise we are way better jumpers becasue we have long muscular legs. $\endgroup$ – John Feb 15 '18 at 7:13
  • $\begingroup$ re brain: cbsnews.com/news/gene-mutation-divided-man-ape "[...]researchers say they may have discovered the mutation that caused the earliest humans to branch off from their apelike ancestors - a gene that led to smaller, weaker jaws and, ultimately, bigger brains. [...] The change would have allowed the cranium to grow larger and led to the development of a bigger brain capable of tool-making and language." $\endgroup$ – Real Subtle Feb 15 '18 at 12:16
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lets answer in order.

  1. not significantly, bone density is not a really good measure of strength.
  2. tool use will be hindered by a climbing anatomy, you can have a hand optimized for climbing or for tools not both, it may be hindered if you make the muscles stronger as fine motor control may be affected.
  3. since the only information we have is "stronger" their weight is kinda up to you. I will say with that height they will not be great climbers, humans are already too heavy for it.
  4. intelligence and climbing do not appear to be related so no.

  5. Yes endurance will suffer, human endurance is so good becasue we evolved for long distance bipedal travel, these have evolved in the opposite direction.

  6. Again with just "stronger" this is up to you.

  7. reaction time is not related to any of this so they will reacts as fast as humans which is normal for animals our size, size is the major factor as it controls the length of the nerve signal, smaller animals react quicker becasue the signal has a shorter distance to travel. of course they will be a bit slower in the limb but that is a fairly minor thing unless they a throwing something, and will not impact reaction time.

  8. this depends entirely on how much you change them to be better climbers, long legs are not good for chimp style climbers but good for jumpers. Humans are good jumpers, chimps are not, so if they still have human like legs they will be good jumpers. Likely around the same as a humans.

"Stronger" is not much help you would have ot say how they are stronger (greater muscle recruitment, larger muscles, better leverage, etc.)

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  • $\begingroup$ So by what means the chimp's muscles are stronger? Is it simply a stronger nerve signal? $\endgroup$ – Christmas Snow Feb 15 '18 at 19:14
  • $\begingroup$ Sort of, since they are signalling the whole muscle instead of just a small part like we can they get more out of their muscles at the cost of worse control, all or nothing, but that also might make their endurance poorer, since they will fatigue the muscles much faster. humans basically never recruit the entire muscle so we never get full strength out of them, oddly it also appears we do get more speed out of muscles this way as well, becasue we recruit muscle groups continuously instead of all at once. so a chimp may be stronger but a human can probably throw a rock of spear faster. $\endgroup$ – John Feb 15 '18 at 21:53
  • $\begingroup$ so chimps have strength humans get speed and control. ncbi.nlm.nih.gov/pubmed/19817225 $\endgroup$ – John Feb 15 '18 at 21:53
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The only thing I'd consider in terms of how strength would affect intelligence would be the size of the jaw muscles. The major difference between humans' and other primates' muscles and bones of the head and neck is a larger cranium that sacrifices muscle volume in the jaw area. This led to our much weaker bite but gave us room to develop a very large forebrain. Hope this helps!

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