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Some Science fiction stories have generations growing up on Mars would be a lot taller 7'+.

How would growing up on a much lower gravity planet affect a mammals size? I understand bone density would likely be an issue.

What are the other health concerns?

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For mammals, things like height are mostly controlled by DNA. So the difference wouldn't be huge. But there would be a few differences.

Size

Astronauts grow about two inches during their time in space. This is because the effects of gravity compress your spine on Earth. When gravity is no longer affecting you, your spine expands again (the spine expands because it absorbs moisture from your blood). This would also happen on Mars, because gravity is less strong. So people would probably be half an inch to an inch taller on mars.[1]

Lighter gravity means less force on us pushing us down. That means our bones would likely get smaller. If our bones didn't get smaller, then we would more easily be able to support bigger weights. Large people would be less heavy and probably more agile.

Muscles

Without the constant fighting of high gravity, our muscles would weaken. If we moved to Mars, our muscles would adapt Mars gravity, so they would weaken. This would be a big deal unless we planned to return to Earth, in which case we might not be able to support ourselves. Our heart would also get weaker, but it would probably not affect us to much because it would not need to be as strong. There would be less fighting it.[1]

Development

Gravity is important for cell differentiation [2]. In other words, for a less complicated cell to turn into a more complicated cell. The most immediately critical effect of this is bone cells. Bone cells have trouble attaching to the bones without gravity. There are speculations that gravity actually helps bone cells know where to attach. Immune cells are also affected, so the entire immune system would be effected. However these effects have only be observed in micro gravity or no gravity. So these likely would only be an issue during the ride too Mars, and the vehicle transporting the people could have artificial gravity.

Reproduction

The biggest problem about low gravity and development is reproduction. When a baby forms, its cells differentiate often. If cells couldn't do this properly, then babies could form.[2] The sperm and egg combining in space is also an issue. The enzyme that causes the sperm too stop when it attaches to the egg doesn't work very well in space. Low-gravity may cause this same issue.[3] There is also an issue that This is, again, more of an issue in micro-gravity, but it should still be considered.


Overall, likely development would be fine on Mars, but it needs to be considered how to safely get there. Also, it is possible that these issues would show up in a more minor form in a low gravity area.


[1]: Main reference article.
[2]: This Wikipedia article.
[3]: This YouTube video does a good job explaining the health effects of zero-g (which could parallel the affects of low gravity).

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  • $\begingroup$ A lot of science fiction has children growing in low-gravity environments growing significantly taller. I don't know if any studies have been done that would confirm or refute that hypothesis but I think that would be a good addition to this question as it's so common. $\endgroup$ – Tim B Sep 24 '14 at 8:20
  • $\begingroup$ @TimB I could find no evidence on that, so I didn't include it. I don't see why we would grow much taller, I'm pretty sure it's genetical. $\endgroup$ – DonyorM Sep 24 '14 at 11:20
  • $\begingroup$ @DonyorM actually genetics is only part of a persons height. Diet plays a huge role and so do different hormones in the body. While you might not get someone to grow 2-3 feet taller, I suspect 6-8 inches is not out of the question. Still really like your answer +1 $\endgroup$ – bowlturner Sep 24 '14 at 12:39
  • $\begingroup$ consider adding: youtube.com/watch?v=jTL_sJycQAA $\endgroup$ – PipperChip Sep 24 '14 at 19:18

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