My humanoid aliens grow and age the same way as humans but it's a much slower process. It takes them 2 years to physically age and grow. If one is, let's say, 50 years old than their human equivalent age is 25 years old. It's easy to calculate their human age. Take whatever number divided by 2. I wonder how long the pregnancy should last (They produce offsprings the same way a humans). In humans, it's 9 months. If I were doubled it, would be 18 months but being pregnant development would be slower. I'm not sure if I want to go there. A 9-month pregnancy is already hard enough.

Here's how it would be:

Infant/Baby: 0-7 yrs (0-3.5 yrs)

Note: There's no toddler

Child: Under the age of puberty (a person is no longer considered a child when they hit puberty)

Note: There's no "teen" or "adolescent".

Adult: At and above the age of puberty

Elder: When hair starts graying


Puberty begins somewhere between 23 (11.5) and 26 (13) years old. There's no late or early puberty. Puberty lasts for (only) 3 years.


You are an adult when you start puberty.

Old Age

You're are considered an elder when you're hair starts graying. It happens sometimes between 76-108 (38-54) years old. Life expectancy is between 160-200 (80-100).

Does the aging make sense and how long should the pregnancy be? (since they age slower)

Note: This is a very humanlike species (with a few anatomical, physiological, psychological, biological, and physical differences). In my universe (real life-based universe), my humanoid aliens are the only human-like species outside of Earth. They are cousins to Earth. Compared to humans, they are technologically and modernly behind.

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    $\begingroup$ There is no question mark in this question. What is the question? (And the word puberty is Latin; its original meaning is "maturity" -- the Romans considered that sexually mature people were adults, with all the responsibilities of adulthood. Observe that English does not have a native word for this concept, which doesn't mean that English people did not undergo puberty before they learned Latin. Also observe that the modern meaning of the word puberty is not the meaning it had for the ancient Romans.) $\endgroup$ – AlexP Jun 19 at 0:33
  • $\begingroup$ What's the difference between a 7 years old kid and a 70 years old adult? In humans the only two differences are experience and physical degradation. Human mentality only deviates from normal during hormal imbalances which can happen and do happen periodically through the life of everyone. Age is just a number on a scale of how close you are to alive or to dead. One could argue that a really old human has the physical strength, vulnerability and the hormones of a child. $\endgroup$ – user76488 Jun 19 at 0:46
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    $\begingroup$ @AlexP I'll edit the post and the question or questions. $\endgroup$ – swilson225 Jun 19 at 0:51
  • $\begingroup$ @AlexP I wasn't aware of the history and entomology of the word puberty. Thank you for telling me about it. $\endgroup$ – swilson225 Jun 19 at 0:53
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    $\begingroup$ @Vesrie: There are many differences, anatomical, physiological and psychological, between a 7 years old child and a 70 years old adult. Children are not miniature adults. There is a very good reason why pediatrics is a distinct branch of medicine. $\endgroup$ – AlexP Jun 19 at 0:55

human aging is not linear. If you want your aliens to age at half the rate of a human, you absolutely can do that. But then you have to take the consequence that pregnancy doubles also. And as you said 9 month of pregnancy are hard enough: evolution would have adapted your female aliens to endure the longer pregnancy (and 'heavyness of pregnancy' doesn't double by consequence).
But humans age differently at different parts of their life. We age realy fast in the belly and in our first years, slowing down more and more when we get older. So if you want to keep 9 month of pregnancy (I would change that, they are aliens at last, no humans ^^) you could change the rate of aging dependant on the age your aliens already have reached. By that you can get nearly every pregnancy-length you want (lets say from 6 month upwarts).

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  • $\begingroup$ I think it would be more realistic to double the length of pregnancy so it would stay consistent with the aging. Like you said, aliens aren't human! 18 months wouldn't be too bad for them. $\endgroup$ – swilson225 Jun 19 at 4:35
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    $\begingroup$ "Growing up" and "getting old" are two completely unrelated processes. Actually, the only thing they have in common is the commonest denominator of every process in the universe: they both take some time. There is no reason why the pace of "getting old" should correlate to the time in "growing up and maturing to adult " or pregnancy time. As a matter of fact, there's nothing preventing aliens for being oviparous, for example. $\endgroup$ – Rekesoft Jun 19 at 7:59
  • $\begingroup$ Also, if you believe the Bible, humans used to live for much, much longer. There's no particular reason why average lifespan should be correlated to gestational period. $\endgroup$ – Matthew Jun 19 at 18:06

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