Killing a trope: Low Gravity Elves and High Gravity Dwarves

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Offline Kedamono

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Killing a trope: Low Gravity Elves and High Gravity Dwarves
« on: August 10, 2019, 10:26:45 PM »
Sources for this post: How much of human height is genetic and how much is due to nutrition?
Reproduction and growth of mice and rats under conditions of simulated increased gravity

I've had this conversation before with some other folks about one pernicious trope in SciFi: Heavy Worlder: Short and stout, Light Worlder: Tall and thin.

But that's only true if you believe in Lamarckian evolution.

Height and weight is about 80% genetics and 20% environment, mainly nutrition. Basically, if both your parents are tall, you'll be tall, and you can get taller if you eat well, mainly protein, as a child and get all your mineral nutrients. So, what does this mean for the tropes? Well, Heavies probably will be more muscular, but they won't be short. They'll have denser bones, and quicker reflexes. (When everything falls faster, you learn to move faster.) And they will probably "weigh" the same as a person on Earth does.

Example: We have two clones, Abe and Ben. Abe is "born" on Earth and Ben is "born" on Planet Example. Planet Example is bigger than Earth, and has a G-force of 1.25 gravities.

When they reach adulthood, Abe is 175cm tall and "weighs" 70kg under Earth gravity. Ben is 173cm tall and "weighs" 72kg under Example gravity. If you look at their mass, Abe is 70kg and Ben is 57.6kg. Ben is far more muscular and has a higher bone density. He has about 2% body fat. And if he visits Earth for a while, his spine uncompresses and he's now 175cm.

Let's look at their other clone sibling, Carl. He's on the planet Other Example, with 0.75G. He's taller, but only by a bit, 177cm. But here's the interesting part. On his planet, he "weighs" 60kg. But his mass is 80kg. In the lower gravity, he's put on weight, because he's never had to work as hard to move or pick up things. He also has slower reflexes, as thing fall slower on his world. Now, he's not proportionally slower, as nerve impulses still move at the same speed, but his reaction time is off. And if he goes to Earth, he'll scrunch down to 175cm. This of course assumes that he maintains the same caloric intake as his clones Abel and Ben. But if he reduces his intake as he grows and matures, he may end up shorter than them.

Of course you'll say, but what about 10 generations down the road?

Well, if you send folks between 160 and 177 centimeters as colonists, that's going to be the range 10 generations down the line.  If you want short Heavies, you'll have to set your height limit to no more than 152cm.

Now if Ben was born on a world with 1.5G, he'd probably mass around 65-60kg on Earth, and weigh between 81-90kg. There's a limit to how much body fat and weight you can lose in this situation.

But, I hope this helps to kill the stereotype of heavy world dwarfs and light world elves.

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Offline ORtrail

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Re: Killing a trope: Low Gravity Elves and High Gravity Dwarves
« Reply #1 on: August 11, 2019, 03:55:13 AM »
Not to mention once you can start tweaking DNA, environment will mean even less.  I could see a future society where NOT checking and altering your offspring's DNA would be considered a form of child neglect.