This answer states that "guided evolution" would help babies develop under constant 3-4g's. This answer has inspired me to ask , what sort of genetic tinkering would help humans adapt to life on a planet with 3-4 G's?

Basic background information:

Humans have mastered star travel. FTL travel and FTL communications have been mastered. It is the late 2300's. Humans have decided to found their first interstellar colony. They have chosen a relatively nearby world with 4G's and otherwise hospitable conditions. Human satellites and drones have been surveying this world and mapping it's continents for decades. It orbits a sun-like star, and has no known indigenous intelligent races. Five thousand colonists have set out to establish a settlement.

Human technology allows massive biological changes. Humans can not only modify their physiology, but also their genes. Essentially, humans can do anything they want to their bodies at a good price. Assuming infinite ability to change their bodies, how can my humans modify their bodies to better adapt to the environment of this world?

For the sake of argument, most of the planetary surface is covered in "grasslands" and is dotted with lakes and small seas connected by rivers. There are some mountains, but very few.

EDIT

I want humans to be able to survive on the surface of the world on the great plains. They must be able to stand upright and must still be recognizeable as humans. We will assume that food is in abundance and all we need to account for is the plains and gravity. If you want to, you can take other considerations into account, such as adaptations suited for the plains, but for the purposes of this question answers should include anything that helps remain identifyable as a human while providing as much advantage to humans over native life as possible. Some ideas for points to cover might be;

  • How would we change our inner biology? Would organs be better placed in different places?

  • Would bone structure require modifications?

  • How would we modify our bodies to help them bear children?

  • What about reducing mass reducing weight and muscle strain?

It must obviously be biologically possible for the human to survive.

  • A related question asking whether humans could survive on such a world. – the_OTHER_DJMethaneMan Apr 29 '16 at 12:58
  • I think there's a number of directions you could go given the description you've provided. Is your purpose for these people to swim great distances? Dive for a long time? Breathe underwater? Run across the length of those grasslands? Tell us and we may be able to give you some ideas. – AndreiROM Apr 29 '16 at 13:48
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    what about something like this, maybe? facebook.com/9gag/photos/a.109041001839.105995.21785951839/… – Zorgatone Jul 26 '16 at 10:51
  • A note, high gravity worlds would give rise to short bushes and moss over grass. Basically grass is to thin and tall to flourish. – Mormacil Mar 20 '17 at 9:49
up vote 6 down vote accepted

Make them shorter.

There are a number of option to consider, however making your people shorter is probably the easiest thing you can do. If you cut people's average weight by just 10 Kg that turns to 30 or 40 on your planet. You have to reduce mass as much as possible so no fat people on fat earth.

Copy the birds. Birds need to be light to fly and need a lot of power to move. Give them strong hollow bones, and powerful muscles. Consider replacing the components of the extracellular matrix that form bones with lighter and stronger materials. Engineer better actin molecules for stronger and more efficient muscles. Your people will also need a very active metabolism since now moving around and everything is 3 or 4 times more energy expensive.

The best way would be to have them walk on all four but you probably won't like this solution.

EDIT: After some consideration this seems like an impossible task. Let's forget about the 4g and let's stick with 3 that is already more than what we can handle anyway.

to survive on Fat Earth you need to:

be short a 155 cm tall guy is already 150 Kg. Cut the sexual dimorhpism; women will have to do with men as tall as them

be skinny as I said no fat people allowed

have hollow, rocket grade bones maybe you can replace the Calcium in hydroxylapatite with the lighter and stronger Beryllium which is in the same group and therefore should be chemically similar

have stronger but not massive muscles As I said engineer better molecular mechanics for muscle contraction. Bodybuilders are also not welcome since we need to cut mass as much as possible.

eat almost constantly or at least eat very very caloric food since now everything is extremely energy consuming and you cannnot afford to store energy as fat.

Your masochists will probably enjoy swimming in the sea since there the buoyancy would give them some relief.

I invite you to take a look at the bone structure of the hero shrew. This little creature can survive being stepped on by a grown man, but from the outside it looks like any other shrew.

Similar modifications of the human backbone are probably necessary to live in high g environments for any extended period of time.

Also, shrews are generally pretty awesome. I'm just saying echolocation, venom, eating scorpions, monster metabolism … well, maybe don't splice it all in.

The gravitational impact isn't on the body, but on every molecule that makes up that body.

That is to say that any bodily process that relied upon "heat rises" or any other such basic concept needs to be revisited.

But generalities..

A lighter body wouldn't work out too well: with higher gravity comes higher pressure, with higher pressure comes increased load bearing requirements for any and all parts of the body...not just as regards your own weight, but atmospheric pressure, the ability to move and influence external masses etc.

You wouldn't want to be short and stumpy: leverage is king, the great muscle multiplier.

Massively more powerful circulatory system: It's not enough to recognize that blood weighs 4* as much, the muscles are also doing on avg.. 4* as much work so they need a commensurate increase in delivered payload.

You'd have to redesign the circulatory system almost entirely, because with that 16*(?) increase in load on the heart you're also creating immensely more heat.

Atmospheric density would require reworking the lungs somewhat, you'd have a much higher oxygen content (assuming the average chemical levels are the same across the entire atmosphere) it being significantly heavier than nitrogen. [with increased gravity the separation between chemicals in atmospheric levels becomes more pronounced/the greater the energy demands are the greater the stratification]

This is a boon for our metabolism, but still not nearly enough to make our lungs sufficient to the task of delivering sufficient oxygen. The best solution...well, hard to say, but I'll tie to:

The energy required for both internal process & external effect will be multiplied, requiring greater resources, but I think it's a mistake to go for "eat more."

See, when we consume (eat, drink and breathe) we don't destroy anything, rather the body transforms one compound to another, creating heat and etc and what the body doesn't manage to use is [largely] dumped out. This is massively inefficient, as the system, when dumping out compounds, could rather use subsidiary processes to reformulate the 'waste' products back into usable forms, separating and re-separating essentially ad infinitum in a closed system.

The whole "tree converts x to y so we can convert y to x" thing can all be performed internal to a single organism, and not just for oxygen and carbon, but for every element and compound required in the operation of the organism.

On the one hand this might provide also a method for using thermal energy rather than extruding it as waste also, on the other this would be even more complex a task than doing the transmutations in the first place, so we might end up with a creature that can't exist at temperatures above -20C or else it would fry itself. So heat management becomes a greater concern than [other] resource management.

The body might be provided with buoyancy devices, not sure how effective such a concept could possibly be, but say.. fluid (as per joints) or hydrogen sacs might help to spread the load or decrease the overall load on the organism's skeleton. I'd imagine that such attempts would require such a volume as to be less than useful, but it's not like I've done the math here.

Really though it seems to me the body would have to be reworked from the ground-up, every membrane has been taken up into the evolved collective because of it's operating characteristics at 1g, quadrupling the energy (not one-shot but permanently) of every particle the membrane is supposed to restrain or redirect is going to have significant impacts.

Specifically childbearing?

Assuming normal human babies:

They would:

Die as soon as they were forced to rely upon their own hearts. Muscle density in babies being what it is, a baby wouldn't even be capable of screaming. Bones would snap even more frequently than adult unmodified humans. Assuming a child survived birth and magically had a heart and lungs that could operate at 4g, its growth would be immensely retarded. It would be blind due to suspension deformation in the eye. Its skull would crush its brain, being too soft and solidifying too slowly to resist gravity's downward stresses. Liquid where it shouldn't be (lungs) would take that much more effort for the lungs to expel.

Let's talk about weeing and pooping?

Your sphincters are designed to hold materials up to a certain pressure, gravity multiplies downward force, ergo..higher gravity makes you incontinent. Not entirely sure if sphincters would give up 4 times earlier, but certainly they would be under more strain earlier.

Disclaimer: The Above Is All Guessery

I just read some of the answers in "related to" questions and have to reiterate the point that gravity does not act upon the whole of a body, but every constituent particle.

It is not like having to carry extra weight on your back..and not like being a 600lb person. The materials, fluids and molecules in a fat person at 1g behave the same as they do in a regular weight person.

Answers like "wear an exoskeleton" don't help hardly a bit, as instead of being 'crushed' to the floor, you're being 'crushed' into the exoskeleton.

If 'live under water' would help, wouldn't we suppose NASA would of built a huge tunnel up into space filled with water so shuttles could sedately swim to the surface? Gravity doesn't stop exerting its influence just because you're in a suspension.

If we put a put a person in a centrifuge pod full of water and turn it on, for instance, the difference we get is that before the person is crushed to the rear of the centrifuge...the water must be force out of the way. Which takes..no more time or effort than it takes a person to move through water under any other conditions.

Can water be compressed? Does it matter? I don't see how it can matter. Pick up a bath full of water. Pick up a bath full of water under 4G. Submerge yourself under water in 4G conditions and you're dead even quicker than in atmosphere. Every one of those water molecules weighs 4* as much as on earth...you are not water.

Perhaps..turn people into jellyfish. Babies could be grown in vats in space and engineered to the desired specs before being dropped.

I mean, it seems to me that 24th century man could do it [hell, if people put their minds to it and discarded any misgivings now we could probably find a way and make it happen inside 40 years [that is, apart from actually getting to this planet], but the result couldn't be human by any but the most generous definition.[not that this is a problem, just pointing out my view of the scale of changes required.]

First of all: your bones would have to be able to carry 4x the load they carry at present, so they'd have to double in radius.

Then your muscles would have to be able to do the active work, so they'd have to increase in volume too, thus adding to the load they'd have to carry.

Then your heart would have to pump blood to these bones and muscles, so it would have to increase in size. It would also have to supply the brain at against this increased gravity. The vessels in the brain and everywhere else would have to accommodate the increased pressure, and that in turn would change the way the capillaries work.

All the organs would have to work harder to support the increased metabolic requirements. Your lungs would have to be able to resist a pressure 4x as great as they are currently designed for.

Pick another, smaller planet - there must be hundreds of billions in the galaxy, and I am sure your advanced technology has gazetted them all by now.

But on second thoughts, with a slight modification of the conditions, it may be doable. The modification is this: the new breed of humans must be recognizably human - but not all the time.

This allows us to use an approach that has already been successfully applied in terrestrial biology for hundreds of millions of years. We simply add a second phase to the modified human's life.

During the first phase, he lives as a human, in an environment such as we're accustomed to - maybe on a nearby planet, or in a special nursery environment on Planet 4G.

Then he pupates, and is transported to the harsh 4G environment, where he emerges in this new phase, inhabiting a body designed from scratch to fit the planetary conditions. At the end of this phase, he dies and is buried on Planet 4G.

There are minor operational points to consider - for example, in which phase does he breed? But these are not important.

This solution came to mind as I watched some butterflies in my garden. Thank them for it.

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    Thank you for the answer frank. This does not, however, really answer the question; unless tagged as reality-check one must accept the premise of the question and answer within given the parameters. Questioning the premise is perefectly fine, so long as you do so in a comment. You can comment once you have 10 reputation. You can always comment on your own posts. If you have questions about the site you are more than welcome to ask them in chat ;) – the_OTHER_DJMethaneMan Apr 29 '16 at 14:58
  • Thank you for the information, MethaneMan, which being a noob here I needed. But what happens when the answer is there is no feasible answer? You can indeed make the modifications, maybe, but the result would in no way look human, which is one of the stated parameters. – frank Apr 29 '16 at 15:06
  • Criticizing should be done in the comment section if you think a question needs it. – the_OTHER_DJMethaneMan Apr 29 '16 at 15:26
  • Point taken, but when I tried to add a comment, I was told I didn't have enough rep points - Catch 22. But see my edited answer now. – frank Apr 29 '16 at 17:20

The major weak points will be tendons and blood flow.

Yes, stronger bones will be good and should be part of the mix. Stronger muscles are necessary but they can be trained. However, the tendons tend to be the weak point as they can tear away from the bones or just snap. They must be strengthened and more strongly anchored to the bone.

None of that is important if you can't get the blood in the feet back up to the heart so it can be sent back around. We should take a page from elephants. The tegument/skin of their feet and lower legs is much stronger than ours. It acts as compression socks so the movement of the muscles of the foot and leg can more efficiently pump the blood back up to the heart.

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