Humans can withstand much more than 2.4Gs although the time is exponentially and inversely proportional (for example, 3Gs is a space shuttle launch for a number of minutes, 10Gs is the maximum force allowed during space capsule landing, but only for a few seconds).
Therefore, I wouldn't say "uninhabitable," but probably less friendly (and not immediately lethal) to humans. Also, different animals have different thresholds -- mice, for example, have a much lower tolerance for G-forces than whales.
I recommend reading "Packing for Mars" by Mary Roach -- very insightful book that discusses all sorts of things about planet habitability, space travel, space suit design, psychology, and among many other things, G-forces.
That's curious... I would have thought a land-dwelling mouse would have more G-force tolerance than a whale living in neutral buoyancy oceans. Are you using that as an illustrative example (eg. mice and elephants), or does that still hold for mice and whales?
You're right, it was a bad example. I just looked through the book I referenced, this is what it said (p. 126):
"...a beached whale will die from an overdose of gravity... The whale's diaphragm and rib muscles aren't strong enough to expand its lungs and raise the now far heavier blubber and bone that press in on them, and the animal suffocates."
It goes on:
"You can see what a rat's organs look like inside its body at 10 G's and 19 G's [in] the February 1953 issue of Aviation Medicine... Anesthetized rats were immersed in liquid nitrogen while riding a centrifuge... Heavier blood in the heart has pooled at the bottom of the organ and weighed it down, elongating it like a wad of stretched Silly Putty... This is why the astronauts lie down during reentry -- so the blood doesn't pool in their legs and feet"
I wish I could say I was using it as an illustrative example... But I just remembered it wrong :)
Therefore, I wouldn't say "uninhabitable," but probably less friendly (and not immediately lethal) to humans. Also, different animals have different thresholds -- mice, for example, have a much lower tolerance for G-forces than whales.
I recommend reading "Packing for Mars" by Mary Roach -- very insightful book that discusses all sorts of things about planet habitability, space travel, space suit design, psychology, and among many other things, G-forces.