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For my world, a group of humans have went and lived underground and set up their own community, my question is what would be their adaptions?

The underground they live in consists of multiple dirt tunnels that connect to large big giants cave systems. There is a water system where water comes down from the top of the Earth and there are big caverns that have water in them.

My biggest concern is whether they would become feral or still continue to evolve regular human intelligence

AOS1981 Leader Of The 1981 Arm
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  • Almost certainly they will be too numerous to list in anything short of a small library. – Ash Oct 16 '18 at 15:46
  • Could you give more details about what this underground world is like? is it a a whole sub-terranian ecosystem? a labyrinth of caves? totally artificial? is it ventilated or not, does it have any light sources, what do people eat etc... the more you can give the better – Ummdustry Oct 16 '18 at 15:58
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    Neanderthal Man (aka "cavemen") weren't sophisticated enough to do that. Heck... we aren't sophisticated enough! – RonJohn Oct 16 '18 at 16:01
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    They would have an underground culture, listening to underground music and forming underground movements. – The Square-Cube Law Oct 16 '18 at 16:36
  • Whiskers. For girls, too. – Alexander Oct 16 '18 at 16:44
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    "Feral and "regular human intelligence" are orthogonal. Are you referring to retaining learning? (Because there's a lot of caveman learning (like making fire and hunting the woolly mammoth) which is highly irrelevant when living in a cave. – RonJohn Oct 16 '18 at 16:54
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    As we learn more, there is no indication that (a) neanderthals were anything other than h.sapiens, genetically speaking, or (b) they were any less intelligent than us. People born into hunter-gatherer societies can and do make the transition to modern urban living, especially at young ages. – pojo-guy Oct 16 '18 at 17:43
  • @pojo-guy they were the distinct species H. neanderthalensis, not h. sapiens (though very closely related). http://humanorigins.si.edu/evidence/human-fossils/species/homo-neanderthalensis – RonJohn Oct 16 '18 at 18:29
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    They are closely enough related for (a) fertile interbreeding and that (b) the techs doing the gene sequencing don't see them as any different from h. sapiens, apart from the same kinds of markers that distinguish any other distinct population group within h. sapiens. – pojo-guy Oct 16 '18 at 19:07

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A list of possible (but situational and by no means guaranteed) adaptions, possible adaptations are by no means limited to the ones listed:

  • Pygmism, since food will likely be scarce and fitting in small underground spaces will be harder without it.
  • Ablinism, or regular paler skin since there's no point having melanin in absence of sunlight.
  • 'Worse' posture and wider hips. Human posture is built for endurance running, this is not necessary underground. Without the need for endurance running other concerns (like safety in child birth) take over.
  • Significantly better eyesight if light is present in some form (to see in dim lighting), degenerate eyesight if it is not (no point having good eyes in the pitch black.)
  • if they do go blind you can expect them to have more developed other sense to compensate, most notably during social interation where eye-contact is a big part of communication.
  • Weaker immune system, not being exposed to the outside world will do that to you, assuming that "underground" is not as bio-diverse as above ground.
  • Larger digestive system, given that fire (and thus cooking) has a good chance of suffocating everyone in the immediate vicinity. Though this does depend on what they eat.
  • Probably sweat less, given most cave systems are quite humid, and thus sweat is less effective as it doesn't evaporate so readily.
Ummdustry
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    You'd want other water retention measures to go with sweating less, caves tend to be bad environments to get human safe drinking water in. – Ash Oct 16 '18 at 16:13
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    I'm assuming they DO have a source of water, otherwise the whole question seems a bit mute – Ummdustry Oct 16 '18 at 16:15
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    There's often lots of water in caves but a lot of it you can only drink small amounts of per day due to the mineral load, or similar. – Ash Oct 16 '18 at 16:18
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    @Ash then people adapted to higher mineral content water would survive. – RonJohn Oct 16 '18 at 16:51
  • @RonJohn That would help with some of it but there's also biological contamination, acidity, salinity, and in some cases temperature. Adapting to the available water will certainly be important but needing less of it will still be a survival trait. – Ash Oct 16 '18 at 16:54
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    +1, but to add to your posture comment: unless all the caves are large enough for comfortable erect walking and stair building, the posture would also develop larger shoulders/collar-bone and pectoral muscles for climbing. The evolution would likely favor arms over legs (oooh, chimps & gorillas). – JBH Oct 16 '18 at 21:32
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A lot of it will depend on their social structure. It's hypothesized that human intelligence evolved from a need to compete with other humans after all.

If your cavemen become less social when they go underground (they won't be able to see each other as well anymore and may become more self-sufficient since there's no environment to worry about), they may well stop developing their intelligence. Heck they might even devolve. There's no need for energy-hungry complex social intelligence if you're alone with your mate foraging for edible fungus.

scohe001
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Humans are perfectly capable of using rudimentary echolocation. The subterranean people could further adapt this ability with better hearing and pitch control. They could evolve a language that is both communicative and part of their auditory visualization process.

Skek Tek
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  • At best humans can use echolocation to find giant walls. Which will be harder in the complex and echoing geometries in caves. And hands do a better job of wall-finding for the purposes of a human. If you mean we can use shouting to find one another, sure, but usually we describe that as “talking”, instead. And it has a few extra advantages over echolocation. – Dan Bron Oct 16 '18 at 21:48
  • Bats can identify forms as small as spider webs in complete darkness. The resolution of echolocation isn't a problem. (Remember: this would be a specialized adaption. Presumably evolved over many generations.) Thanks to doppler shift and pressure falloff (which is inversely proportional to distance) it wouldn't be difficult differentiate useful echoes from incidental ones. – Skek Tek Oct 17 '18 at 13:34
  • Yes, bats can. I was taking issue with your statement about humans being able to. I aware that echolocation exists and functions; I am disputing that humans can do it. – Dan Bron Oct 17 '18 at 13:38
  • https://en.wikipedia.org/wiki/Human_echolocation , https://visioneers.org Daniel Kish: "had his eyes removed at the age of 13 months due to retinal cancer. He learned to make palatal clicks with his tongue when he was still a child - He is able to distinguish a metal fence from a wooden one by the information returned by the echoes" Juan Ruiz: "The episode showed him capable of riding a bicycle, avoiding parked cars and other obstacles, and identifying nearby objects. He entered and exited a cave, where he determined its length and other features" – Skek Tek Oct 17 '18 at 15:24