So, in my world, humans were imported to the world about 20.000 years ago. The planet was terraformed to be an earth clone and has 2 Supercontinents.

Basically, I need traits that could have emerged naturally in humans, and that either don't reduce or increase the chance of successfully procreating(Im aware this also depends on local environmental and other selection factors).It would also be great if you point out any non-obvious drawbacks and side effects of these traits.

Now, I already decided that one of these subspecies would have a higher muscle density(10%), and I'm playing with the idea of changing the proportion of the tibia and fibula in comparison to the thigh bone, to create leverage against the ground, making them faster runners at the expense of endurance. But now I'm kinda stuck, so that's why I decided to give posting here a shot.

Edit;at request of john

When People first arrived, they had the same technology they had on earth, like spearthrowers. The first civilisations formed about 5 thousand years ago. Nowadays, castles are obsolete, however, guns never really got going, leading to crossbows being used alongside Napoleonic-era cannons. As there are no steam machines, society is mainly powered by humans(they have developed pedals),animals,windpower and watermills.

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    $\begingroup$ if it is not effecting procreation, then it is just drift and will have no coherent pattern. If you want people to be better at X then X needs to effect procreation, thankfully almost everything does. The technology and conditions on the planet will also have strong effects. I suggest trying this in the sandbox first as right now this question is self-contradictory and vague. worldbuilding.meta.stackexchange.com/questions/7183/… $\endgroup$
    – John
    Apr 16 at 13:44
  • $\begingroup$ It cant affect procreation negatively, it needs to either be a neutral or positive mutation. I'll add information about technology, thanks for pointing that out, i`ll also use sandbox next time,wasnt aware of it. If i may ask, what is the self-contradictory part? $\endgroup$
    – Styx
    Apr 16 at 13:55
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    $\begingroup$ You are talking 1000 generations. That is not enough to be divergent from human on a general scale, so you won't have subspecies at all. It is well enough to have a selection for traits. What traits that would be is your choice, but that would make it opinion based unless you can give us hard factors. $\endgroup$
    – Trish
    Apr 16 at 15:19
  • $\begingroup$ Australia was settled... about 40-20 k years ago. $\endgroup$
    – Trish
    Apr 16 at 16:07
  • $\begingroup$ Welcome to worldbuilding! I like the question, but since you're asking for an open-ended list (verboten on this site) I suspect you are going to get closed. I left you an answer with general advice (not a list) to help you put together your own stuff. $\endgroup$
    – DWKraus
    Apr 16 at 17:08

2 Answers 2


Social Adaptations:

While a 'mere' 20,000 years isn't enough to cause radical speciation in humans, selection will favor existing body types well adapted to regional differences. New archaeological findings suggest but don't definitively prove that human habitation of the new world might be close to the timeline for your settlers, so think of those levels of changes. That will be time for ethnic differences to arise like skin tone, eye color, certain builds (perhaps short and compact in mountains, tall in plains, small noses in cold climates, long arms for swimming in coastal areas, tiny on an island) but it won't be time to get really big changes. A rare mutation here or there will give rise to small changes, but not big ones. Think of the assumed limits of human ability, and then imagine an entire population with one of those abilities. THAT will be your limit. But remember, there needs to be pressure for them to be that way, and other traits might suffer.

  • Founder effects might allow for quite extreme levels of differences as desired. Any human trait can be logically taken to it's extreme if we assume an individual group had several members with a given peculiarity. So a group founded by several members of a family with extraordinary lung capacity and tolerance for holding their breath might give rise to a whole population of subsequent people who, in an aquatic setting, are amazing divers and swimmers.

But what you might see are radical social changes arising in how people relate and function towards each other. Heavy competition for resources in one region may create an aggressive, warlike culture, while expansive deserts may create a culture that highly values kindness towards guests and systems of obligations (especially within ethnic groups). An isolated region with few predators and abundant resources might give rise to a Bonobo-like culture based around sex, cooperation, and a stronger matriarchy to egalitarianism.

Think about the environments that will show up on your planet. The land concentrated in two large continents will likely give rise to one or two very large seas. Think Polynesian culture. There may also be large deserts forming due to extensive inland zones, so consider the cultures that have arisen in desert regions.

  • At 20,000 years ago, subspecies of humans likely existed and may have been part of your migration. So research Denisovians and Neanderthals. Subgroups we haven't even speciated might represent quite different populations on your world if given a chance to isolate. Our assumptions are that these groups would be more primitive, but many of these groups had sophisticated tools and could simply have had traits that made them less adaptable or less aggressive. Even groups like the hobbit people could have (at least in theory) have still existed in isolation until this period, and remain undiscovered by modern science. The tools of Homo floresiensis were comparable in technology to the "modern" humans of the same period.
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    $\begingroup$ Australia is also in that timeframe. Europe to china was about a 10-12k gap in divergence $\endgroup$
    – Trish
    Apr 16 at 16:17
  • $\begingroup$ Thanks a ton, this is helpful. While Neanderthals and Denisovans were already extinct by that time, the point that there might have been other, not jet discovered groups is something I wouldn't have thought of, and i now got a few ideas. $\endgroup$
    – Styx
    Apr 16 at 18:52
  • $\begingroup$ Also, it would help to start with humans with existing wide genetic variability. The more existing variation, the more likely you are to have selection pick variants that make a difference on this new world. $\endgroup$
    – David R
    Apr 17 at 13:58

Basically, I need traits that could have emerged naturally in humans, and that either don't reduce or increase the chance of successfully procreating

There is a wide range of possibilities. Taking your request literally, a specialization of the vomeronasal organ so that humans are more attracted to those with whom procreation would be easier, and also are more able to attract them.

More efficient running is already an established genetic variant (these are actually several different genes, but no one ever got round to breeding for them in humans: polymorphisms in the ACE-encoding genes, variations such as R577 in the ACTN3 gene, and even spleen size and structure - some small populations in Cuba, the Caribbeans and Indonesian Bajau can trigger a 'turbo mode' to delay oxygen depletion).

So, given a sufficient genetic diversity to start with, and the pressure to do so, I think there are few limits to how far humans might change. For a comparison, consider how the canis genus has been bred in the last ten thousand years (granted, dogs reach their sexual maturity ten to twenty times faster than humans, but still); and the first nine and a half thousand of that has been done without knowledge of genetics, much less gene manipulation.

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    $\begingroup$ in the 50 000 years we have dogs we had 10 000 generations of dogs to select for traits. Those humans had only 1000 generations to select for traits, so diversity of humans would not reach that level. Also, breed selection is a very strict selection process: what does not benefit the wanted result is culled. Natural selection takes about 5-10 times longer for the same effect. $\endgroup$
    – Trish
    Apr 16 at 15:23

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