My Kepler Bb humanoids develop cognitive, social, and motor skills faster than humans. Their growth rate though is slower than it is in humans. And they are physically gender neutral until 5 years old(the only way to tell gender before 5 years is via a genetic test).

1 very important motor skill that is absolutely essential for living underground is climbing. The baby room has rocks that go from the crib to the chamber right above it. This helps them climb.

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It is kind of like a human child climbing a tree except that with shorter arms, many more rocks are needed.

But yeah, these babies are able to climb at 2 months old(or so I thought). Just to put that in perspective, the year on Kepler Bb is 20 months long and a 2 month old human baby can't do much other than smiling and push ups.

So that means that they would have to be able to get up by themselves practically from birth or at least a few weeks after birth.

A newborn standing in just a few weeks is a bit too much in my opinion.

So I have these major motor milestones so far:

2 months: Climbing

3 months: sitting without support

6 months: standing without support

9 months: walking

1 year: running and jumping

What should I do about this climbing milestone? I still want it before 1 year old(so before 20 months) and I want it as early as it is plausible. But if climbing requires that the baby gets up, than that would require the baby to be able to stand up(and not just as a reflex).

All these other early milestones look like they are at a reasonable point in time, it is just the climbing that looks like it is at an unreasonable point in time. So how early is climbing plausible given that these babies can stand up on their own at 6 months?

  • $\begingroup$ I would not find it to be too surprising if these humanoids could stand within a few hours of birth. Giraffes do, and these seem to be an advanced form of humanoid, why wouldn't they have engineered or evolved such traits? After all, climbing and hiking/jumping/skipping and/or various other athletic skills would seem to be complementary for survival in a harsh environment. $\endgroup$
    – Nolo
    Commented Apr 1, 2017 at 5:46
  • $\begingroup$ the major reason humans are bonr so underdeveloped physically is the limit of fitting our head through the mothers pelvis, if human did not have to push our giant (brain) head out of such a structurally important set of bones we could have much more physical development as well. As long as your humanoids are not earth vertebrates they do not need to worry about the same constraints becasue their bones and anatomy will be different. $\endgroup$
    – John
    Commented Apr 1, 2017 at 15:24
  • $\begingroup$ Whx do you assume that climing required standing? Keeping your balance might be much harder than grabbing and pulling. I don't know your species anatomy but I think you can sell this as realistic $\endgroup$
    – BlueWizard
    Commented Apr 1, 2017 at 19:51

3 Answers 3


A good comparison for development milestones in climbing humanoids would be chimpanzees. Luckily, the Dallas zoo tracks the development milestones for their young chimps. For young chimps, climbing begins around 5 months, about a month after they start crawling around on their own. This is also the point in time when they take their first non-quadrupedal steps.

Carrying this over to climbing humans, they'll probably start to climb around the same time as they start to walk. Based on your development chart, this will probably be around 9 months of age.

One other important thing about baby chimps is that they aren't left on their own on the ground. Instead, they tend to cling to their mothers or other older relatives most of the time, which they're capable of doing from a much younger age than they can climb from. Climbing humanoids would probably do something similar, since my guess would be that this stage of development is important for developing grip strength, which is critical to climbing ability.

  • $\begingroup$ In human infants the palmar grasp reflex is sometimes thought to be a remnant of the instinct to cling to the mother's fur. $\endgroup$
    – AlexP
    Commented Apr 1, 2017 at 0:36
  • 1
    $\begingroup$ Agreed. The reason human babies take so long is because we sacrificed to be able to develop as big of a brain as possible first, then we learn how to use it. $\endgroup$
    – Cort Ammon
    Commented Apr 1, 2017 at 1:07

To be able to climb, you also need to be able to control your back muscles. this is also needed to walk or crawl.

Else you would just rely on your arms and legs to move your body around with a loose abdomen.

In your development line, this appears to be between 3 and 6 months.


What is their native environment like? Why the need to climb?
You mention that the nursuries have rocks which lead up from their cribs.

Consider kangaroos: when born, the fetuses must climb up from their mother's uterine portal to the pouch on her belly. There, they attach themselves to a nipple from a mammary gland and continue to grow. They won't be developed enough to stand, much less hop, for several months.

Are these humanoids of yours placental, marsupial, or some combination? Well, that doesn't really matter all that much; marsupials can have a smaller birth weight but they require earlier development.

You didn't mention the developmental milestones for a few other things, like rolling over or crawling — it looks like we could place those at 6 weeks and at 5 months, respectively. However, that doesn't necessarily matter:
If the environment in which these infants are required to climb does not require them to use the postures and movements necessary to crawl or turn or sit upright, then there's no reason why they couldn't be able to do so much earlier than those other things.
The environment being conducive is quite necessary, though, unless your humanoids go through different development compared to us: e.g. lower birth weight, earlier development of torso compared to hips and legs.

  • $\begingroup$ Their native environment is mostly underground chambers but if you mean outside of those chambers, it is grassland surrounded by forest. They need to be able to climb because otherwise they could be stuck in a deep underground chamber. It is 1 thing to go from the baby room to the knitting room(not much of a slope here). It is another thing to go straight up to the chamber above it. And these humanoids of mine are placental humanoids. $\endgroup$
    – Caters
    Commented Apr 1, 2017 at 10:56

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