Subtitles section Play video Print subtitles This episode of DNews is brought to you by Subaru. I'm pretty tall, a six-two or so, but there are people who are smaller… Amy for instance… but there are also HUGE in comparison. Just HOW BIG can we get? Height is a big deal. It affects every aspect of a person's life from their own perception of the world to how they're perceived. It's a pretty common misconception that people were shorter back in the day, but it's simply not true. 1,000 years ago people were as tall as we are today, but during the 17th or 18th century, nutritional deficits during youth caused humans to shrink 2 and a half inches on average. Dietary hardship, climate, and disease throughout history all affect height. People were NOT shorter in the past, but had the potential to be as tall as we are now; though, humans do seem to have some kind of unofficial upper limit. The tallest known person in history was Robert Wadlow. He stood 8 feet 11.1 inches (2.72M) and was almost 200 kilos when he died at 22 in 1940. The man was massive. The current "world's tallest man," is Sultan Kösen from Turkey, and he has the same disorder as Wadlow, a tumor on his pituitary that causes it to squirt human growth hormone into his body; increasing his height abnormally. The reason we don't just keep getting larger is, we have to live in the world. Gravity is constantly pulling us down, requiring our bodies to create bones which counteract that force. It's all about balance. We're reaching the upper limit for human height because more weight requires larger bones, which requires more bodily resources to maintain. As an animal grows, its support structure must grow with it; which means bones and muscles must thicken; which can only happen so much. Plus, seven to eight percent of your body weight is blood, so if you weigh 200 kilos, like Wadlow, you'd have 14 kilograms of blood. That blood needs to be pressurized, and pumped, which as size increases, it gets more difficult for the heart; so it needs MORE muscle, and there's only so much room in the human body. Elephants and giraffes have highly pressurized circulatory systems, to keep their blood flowing! Whales can grow larger than us because they don't live on land! The buoyancy of the water around them helps support their weight; while their bones give structure to their body. Air buoyancy is extremely low, only about zero point one two percent of your weight at sea level, where the air is thickest. If our air was thicker, it would help hold us up, allowing us to grow larger, but it would have to be a LOT thicker, which could affect our ability to breathe it in at all. In space astronauts gain a little height, growing as much a 3 percent taller because the fluid in between the vertebrae relaxes and expands when not under the load of gravity. For someone like me that could mean adding another 2 or more inches. On Mars, where gravity is only 38 percent of Earth, you'd also get taller. But if children were sent to Mars, they'd get big, but Earth gravity would be a struggle of real proportions. So they'd kind of be stuck. If we lived under the water could we grow larger due to the buoyancy? Maybe? But we couldn't walk on land at all because our bones would break due to the lack of support. This is also why insects are limited in size; exoskeletons can only grow so large before they're too heavy to support themselves! If you could be a giant safely, would you want to be? What's your ideal height?