The (female) human body is pushing the anatomic extremes to support, later bear and nurse a baby while maintaining upright posture and bipedal walk. I cannot see a way to realistically make pregnancy last any longer, which some SF writers did to explain further evolved über/super-humans or mutants – a term which I would consider slightly derogative now. I’m considering either a prolonged or a second puberty instead, but I’m not sure when these phase of physical change would occur (i.e. before or after the “fertile years”), how long it would last and what exactly could develop realistically and how it would differ for the sexes.

  • pregnancy → infancy → childhood → adolescence / puberty (→ here?) → adulthood / parenthood (→ here?) → menopause / andropause → decay

For the record, I’m not thinking of mutants with individual “abilities” as depicted in X-Men or Heroes for instance, but a new generation of “growing”, more sapient human beings in general. I‘d like to get these people a larger brain (and head) with second puberty to explain increased mental powers, but other organs would probably have to grow accordingly. Any new organ seems unrealistic to me or it would have to be there (in minimal form) at birth.

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    $\begingroup$ It's not clear to me that a second puberty is necessary since these alter-humans can just extend the first puberty to give them greater brain power. $\endgroup$ – Green Oct 16 '15 at 15:30
  • $\begingroup$ @Green Yes, that’s one possibility which I termed “prolonged puberty”. $\endgroup$ – Crissov Oct 16 '15 at 15:45
  • $\begingroup$ Sorry, I missed the possibility of a prolonged puberty. $\endgroup$ – Green Oct 16 '15 at 16:20
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    $\begingroup$ You might find Larry Niven's Pak Protectors interesting: en.m.wikipedia.org/wiki/Pak_Protector $\endgroup$ – Mike Nichols Oct 16 '15 at 18:13
  • $\begingroup$ @MikeNichols Indeed. Among others, I once had a rough concept for a humanoid species that changed sex over time: presexual childhood → gynsexual youth → bisexual transition (menopause) → androsexual adulthood → postsexual seniority. Each phase would last ten to twenty years. I also tried to combine it with a cogenitor concept. $\endgroup$ – Crissov Oct 16 '15 at 19:48

There is no reason for pregnancy to last longer, if you consider just how much of a child's development happens after they are born. In fact there is no reason anything needs to take longer for increased mental faculties to develop, it just means the brain has to grow more or faster.

There's also no reason a new organ could not grow over time, although you are right that in most cases the organ exists but is tiny and then starts growing larger at a certain stage of development.

There are two possible ways this could go, and the deciding factor is what the cost of this increase mental power is.

If the larger brain and increased abilities has a high cost (for example more calories needed etc) and will somehow hinder reproduction then most likely it will happen after parenthood.

If the larger brain and increased abilities provide more benefits than cost and so help reproduction then it is more likely to happen before parenthood.

It really is that simple. You need to look at the advantages and disadvantages of the changes. You can then decide whether it will improve breeding fitness to have them happen before parenthood to help with your own children, or after parenthood to help with your grandchildren.

After all just a few "deep thinkers" in a small village would probably be enough to take the "village elder" role and advise the others, giving everyone the benefit of their increased intelligence without the cost of supporting big brains for all.


The reason human infants are born so underdeveloped now is because of our brain size. It is the limiting factor in how large an infant can be.

So lengthening pregnancy would actually increase the risk of severe trauma or death to mother or child.

Now a prolonged puberty would actually make more sense since this is already a changing time in life. The point of most biology is to successfully pass on genes to the next generation. Once that has been done, what is the point of the person? So other than genetic manipulation why would there be a stage later in life to 'improve' an individual? It would have to provide some kind of extra boost to the survival of the offspring (most likely).

Now Maybe it's something like menopause, where parts of the body shut down and quit working (because aren't needed any more) and the extra resources are spent on other areas, such as brain power. Maybe happening in the late 40's when grandchildren might be benefiting from the extra smarts?


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