What constitutes a "giant" in your mind? Certainly, people who are 6 to 7 feet tall are commonplace nowadays, unlike the Middle Ages, or even a hundred years ago. But what about someone who's seven feet tall or more? We may call them "giants" in jest, but it's not the same as when we think of the giants in our legends. A measurement of more than seven feet is rare, but there are plenty of healthy people living today in that range that prove it's not so legendary by our contemporary imagination. Rarer still is a human that's eight feet tall, but there has been one in recent history: Robert Pershing Wadlow stood 8' 11.1" tall (2.72 m) and weighed 490 pounds (220 kg) and showed no signs of stopping his growth at his untimely death in 1940 at age 22. So it's possible that a height for a human can approach nine feet, but could any height beyond that be sustainable?