Hopefully this isn't two separate questions - I do feel like they are interconnected enough that they can be counted as one. I'm wondering if it would be possible for primitive human ancestors.

Let's say around 6 million years ago, a species similar to the Orrorin tugenensis (which from what I understand can be considered one of our earliest ancestors), decided to move into the water for reasons (competition from other species, some kind of natural disaster at surface level, whatever it is). The assumption is that the water would be safer and just overall better for them than the surface would be.

How would this primitive species adapt and build a civilization underwater? SOme thoughts I had:

  • Maybe they live near hydrothermal vents, their "fire" underwater and build their civilization around those
  • Maybe they actually found a network of underground tunnels that have pools that provide deeper access to the sea

Anything else that could exist that would allow such a civilization to flourish? (both in terms of physiological changes over millions of years as well as infrastructure)

  • 2
    $\begingroup$ how are they getting air? $\endgroup$
    – John
    Commented Nov 4, 2019 at 2:46
  • $\begingroup$ They won't have much of a civilization, no fire means no pottery, no metallurgy, no real chemistry, no way to store food. $\endgroup$
    – John
    Commented Nov 4, 2019 at 2:51
  • $\begingroup$ @John, we've looked at underwater fire in the past $\endgroup$
    – Separatrix
    Commented Nov 4, 2019 at 14:06
  • 1
    $\begingroup$ @Separatrix generating heat and generating usable fire are very different things, there is also a question about forging underwater, and the answer is it is not the heat source that is the problem. the same is true for pottery, chemistry, and storage. worldbuilding.stackexchange.com/questions/108461/… $\endgroup$
    – John
    Commented Nov 4, 2019 at 14:20
  • $\begingroup$ You might consider the aquatic ape theory which holds that at some point our ancestors evolved on the seashores, thus explaining some key differences from other great apes: notably that we have much less fur, can swim better, etc. In your story, you could posit that this theory is true, and maybe there was a branch of the family tree that moved right into the oceans. $\endgroup$
    – workerjoe
    Commented Nov 4, 2019 at 16:36

2 Answers 2


Cetaceans took almost 50m of years to "converge" to the fish-like stricture we see, 6 millions is very small in comparison. They must have retained their limbs, with perhaps smaller arms. Losing hair (hypo, elephant) is also a common trait of mammals going back to the water. They DO NOT BREATHE under water and developed a more carnivorous diet then we did.

They probably avoid open sea, since they don't swim that fast and have a better hearing, perhaps experiencing music (later developed) in another level.

Their world, unlike ours, is TRULY 3D, so they have a better sense of depth, also linked to they're good hearing, but unlike dolphins they have to train echolocation (blind people actually do that, look it up).

Their homes are floating, submerged (underwater bubbles) or fixed in the coast of the body of water. They spread across the seas long before humans left Africa from the point where they became aquatic, following coastal lines, low depth sea and using nearby islands, so they are very diverse.

They exchanged with humans from the time humans turn their eyes to the sea. They were hunted down by us, several subspecies were extinct in the last 200 thousand years and some still remain, probably the ones better adapted to compete/cooperate/learn with human societies, perhaps we enslaved one or two subspecies.

They were inspired by human technology and vice versa, developed their own language, religion and science and currently occupy most of small islands/flooded low altitude depressions of the world.

They probably construct channels into the land and/or flood it to have "more coast" and water/land interface to build their homes. Submerged bubbles and ventilation systems are used in far of coast areas. Points of air entry are TIGHTLY GUARDED, since they are obviously a vulnerability of the underwater community.


For one thing, if the apes became aquatic, they would probably switch to a purely carnivorous diet, unless they ate sea grass like manatees.


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