It’s very likely that greater gravity would limit the size of animals to a more optimum power to weight ratio.
And morbidly obese people generally stop moving and exercising. Eventually they get to the point where they can’t even get out of bed. There are plenty of strong fat people, but you aren’t morbidly obese if you can still get up and walk around.
Anyway, I think a 2 g planet is past the point of survivability. That’s carrying around twice your weight. Maybe really small people could survive, but a 200 pound guy would weigh 400 pounds. At that weight you’d just stop walking and even if you kept moving by the time you were 20 your bones and joints would be destroyed. How can these people get any work done? How can you farm when you can barely get out of bed in the morning? Can you imagine going through pregnancy? How many children could you birth on a 2 g planet? How many children would live to see adulthood? How many of those children would have the physical strength to raise more kids?
And if you assume a super-high-tech civilization where everything is done by robots, well, why are any people living on this hell planet? Just live in orbit and do everything by remote control.
Possibly the second or third most intelligent post in this thread.
Look, we don’t really know what the developmental effects of regular high gravity would be (other than limited experiments on poultry) but it’s not a stretch to guess that bones will be denser, skeletal muscles will be stronger, stature will be shorter and squater, et cetera. We would expect that residents of such a world would be somewhat stronger in a 1g field than people native to Earth, although I don’t know that they would be “super strong”…just more acclimated to high gravity in the same way that an athelete who trains at altitude has a greater capacity for respiration than his twin brother at sea level. One factor to consider is the effect on heart action; inhabitants of this world are going to have to cope with higher blood pressure and greater respirtory demands on their system.
The evolutionary angle is a non-starter for the first few generations; people with physiology totally incapable of surviving in such a field (weak bones, poor muscle development, congenital heart or joint defects) would be weeded out quickly, but I wouldn’t expect any significant evolutionary changes in the short term–just a tendancy to favor the stronger members of the existing pool. Long term, people with stronger, stouter joints, muscles, and hearts would come to predominate.
I suspect 2g would probably be too heavy for infant and childhood development, though, resulting in many physiological problems, and I’m morally certain that no woman would want to subject herself in pregnant state to such a field. (Aside from the carrier, however, I don’t know that it would have a significant effect on prenatal development–the fetus is essentially suspended in fluid, and while the heavier gravity may have some effect I wouldn’t guess it to be horribly detremental.)
As Lemur866 astutely points out, if you’ve the ability to travel across the void of interstellar space, you don’t need to inhabit such a world (even assuming it has resources that are somehow worth propelling out of such a deep gravity well). You can remain in orbit indefinitely, either in free-fall (the medicaly science of which has presumably already been worked out) or in a rotating habitat to simulate whatever level of gravity appeals to you the most.
Stranger
My sister did the high-G experiment for a school science fair. We rigged a centrifuge, hung the mouse cage on one spoke (counterweight on the other) and let the little buggers (that’s mice) breed and grow for about 6 months. That’s several generations of mice. We calculated the environment at 2.5 G. They were flatter than 1 G mice, but pretty much lived their normal lives (didn’t check life span), running around, jumping to the top of the cage and back down, that sort of thing.
Mindful of the “bigger is different” warning, I’d still expect that humans could live and survive nicely at 2 G or so. They’d have lots of medical problems, as detailed above, but the survivors would have one hell of a handshake.