Expert: Walter Hintz - 2/6/2008

Question
I wondered if you could tell me something about the affects of size upon an animal, in particular a human. Would it be possible for a human being to exist say, if he were a hundred feet in height?  I don't mean in regard to his impact upon his environment, more to the basic needs and operation of his body.  I'm thinking of the affects of gravity upon the body we now have?  Would a larger body retain heat better?  Would our feeding habits be radically different?  And conversely, could we survive if we were much smaller? Disregarding the obvious threats from numerous predators.  I guess the our size is perfect for our particular surroundings as there are so may of us!  Thank you for your time.
Sincerely Mark

Answer
Hi Mark:
We are as we are because that is what works best for survival.  With regard to size we are subject to the Laws of physics, chemistry and biology. Our skeleton is subject to stress that limits our size.  The man recorded as the tallest was Robert Wadlow,8'11.1". He needed leg braces to support his weight of 491 pounds.  In died from an infection when one of the braces caused a blister.  There are some men now claiming to be bigger but the limit is less than 9 feet.
You are correct that greater means greater heat production and graeter energy requirements.  Wadlow required 8000 C per day.
As to small size there does not seem to be a limit.  Preemie babies are small and survive with care.