I have a planet I'm working on which is inhabited by war tribes. They fight all the time. They can hunt and farm a little bit but they mainly fight to the death. There are billions of these beings on this planet (they reproduce quickly). I figured I can only keep them fighting if there was nothing in between them, mainly water.

Would a large rock world with a few large lakes be sustainable for life?


I want them to look grey and smaller than normal humans but not be dwarfs. I need a reason for somewhat intelligent beings to look grey. How can they evolve to be grey?

  • $\begingroup$ You should remove question 1 and ask it as a follow up to this question. Both questions are large enough to be on their own, and the answer to 2 may affect what answers are viable for 1. $\endgroup$ – Tezra Nov 29 '16 at 17:04
  • $\begingroup$ Agreed, there are two questions here. The second one should ideally be broken out. $\endgroup$ – superluminary Nov 29 '16 at 17:11
  • $\begingroup$ Going in for the Star Trek reference. The adult version of a tribble. I am concern that the larger the being, the longer birth and growth to adult hood takes. Either food shortages or shortages of adults could dramatically reduce the population. As long as the lakes don't evaporate over time and not get replenished water shouldn't be a big issue, except if each one drinks 2 cups of water a day that is 500 million gallons of water each day per billion. Most humanoid lifeforms can't go more than a few days without water, so many could die from dehydration. $\endgroup$ – cybernard Nov 29 '16 at 17:21
  • $\begingroup$ If you want grey people, you need to fiddle with their system's star (and possibly planet's atmosphere absorption spectra). Black/brown/white skin is an adaptation to sunlight. At equator there's too much light, at polar circles, there's too little. Africans have black skin as protection from UV, Scandinavians have pale skin to let more UV in. With right star spectral type and luminosity, you might get a setup which would cause plausible grey skin. $\endgroup$ – M i ech Nov 29 '16 at 20:01
  • $\begingroup$ By "lakes", do you imply that there is no salt water only fresh water? Or do you accept seas as large lakes? The lack of salt may have an impact on formation of life. $\endgroup$ – SRM Nov 30 '16 at 3:07
  1. Earth is a rock with one large lake. We call it the ocean. The numerous inhabitants fight each other all the time over material or immaterial things (although they are generally of various shades of brown, not gray).
  2. Animals can evolve to be gray in the same way that they can evolve to be brown, green, red, striped, spotted, dun, yellow, large, small, quick, slow, etc. etc. For example both rats and wolves are gray. It happened that we evolved to be brown (from very pale brown to very dark brown with all shades in between); it's an accident, it does not have to have a reason.
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    $\begingroup$ And there have been times in the past where the 'islands' (that is, the continents) in that large lake have formed a single mass. See Pangaea. Even today, Europe/Asia/Africa is a contiguous land mass, as are North & South America. $\endgroup$ – jamesqf Nov 29 '16 at 18:04

Only answering the question, 'can life live on a world with little water', the short answer is yes, but probably not life as we expect it. 'normal' (Earth like) life would only be able to thrive near the lakes (like an oasis in a desert).

As for the rest of this world, they would have to use a non-water based form of energy storage. We know alternate methods exist, for example Chemosynthesis bypasses the need for light (but still uses water).

You might want to look into ideas like silicon based life-forms

Also read this answer for another, well detailed, alternative.

A touch on skin color, Skin color can be kind of random, but usually the skin color ends up being whatever color best helps them survive. This can be things like natural pigment/biologically cheapest, provides a level of camouflage, bright colors to warn you are dangerous (poisonous), or even just that species decided it finds a specific shade of grey 'sexy' (like peacock feathers)

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    $\begingroup$ @Zxyrra, I read "large rock world with a few large lakes" to imply that water surface area is negligible compared to on Earth. Less surface area = less heat absorption = less evaporation = less rain. So water will probably only be accessible in meaningful quantities near these large lakes. Earth life would thrive near the lakes (like in my opening paragraph), but living away from the lakes would require a different biology. So How much Earth life and abnormal life would depend on the size/frequency of these lakes. $\endgroup$ – Tezra Nov 29 '16 at 21:51
  • $\begingroup$ My bad, I jumped the gun on reasoning it out, you're right. $\endgroup$ – Zxyrra Nov 29 '16 at 22:00

Most human life would be clumped around the big lakes, but were there are lakes there are rivers so human life would not just be limited to those lakes it could also developed along side the rivers that spread out from it.


If a planet had diffrent crustal composition, more felsic rock less mafic rock, or for laymen more granite less basalt . it would not have the huge ocean we have now but lots of more isolated "seas"


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