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Why do humans walk on two legs? |
by Mya Kagan (whyzz writer) >> more about the author
Have you ever noticed that lots of animals walk on four legs? Dogs, cats, rhinos, giraffes, horses, mice, and more! So if lots of animals are using four legs… why do humans just use two?
Scientists have lots of theories and ideas about why humans walk on just two legs. Most theories agree that humans evolved over a long, long time (thousands of years) from other primates, which refers to animals such as monkeys and apes. (Can you see any similarities between humans and certain primates?) Most primates “knuckle-walk” on all fours, but some are known to stand upright from time to time, just like we do, especially for certain tasks like walking through bodies of water or when carrying food.
Most likely, humans evolved to walk only on two legs at all times because it gave them some sort of advantage! There are lots of ideas about what these advantages might have been. Some scientists believe that walking on two legs used up less energy. Others say it allowed us to carry and use tools. It might have also let us stay cooler (less of the body got direct sun when walking upright) or to see further than when being close to the ground.
No matter what the reason was, we do know one thing for sure: Walking on just two legs has become pretty handy for humans!
Scientists have lots of theories and ideas about why humans walk on just two legs. Most theories agree that humans evolved over a long, long time (thousands of years) from other primates, which refers to animals such as monkeys and apes. (Can you see any similarities between humans and certain primates?) Most primates “knuckle-walk” on all fours, but some are known to stand upright from time to time, just like we do, especially for certain tasks like walking through bodies of water or when carrying food.
Most likely, humans evolved to walk only on two legs at all times because it gave them some sort of advantage! There are lots of ideas about what these advantages might have been. Some scientists believe that walking on two legs used up less energy. Others say it allowed us to carry and use tools. It might have also let us stay cooler (less of the body got direct sun when walking upright) or to see further than when being close to the ground.
No matter what the reason was, we do know one thing for sure: Walking on just two legs has become pretty handy for humans!
Bipedal power!
The more scientific term for “walking on two legs” is “bipedal.”
Think about some things you do every day, and how they would be different if humans weren’t bipedal! What would it be like to eat your breakfast or take a shower if you were standing on all fours?
Consider some of the benefits and some of the disadvantages to being bipedal. How would our lives be different if we’d never evolved to walk on just two legs??
- Connor, Steve. “The truth about why we walk on two legs: it saves energy.” Science. 17. Jul. 2007. The Independent. 13 Dec. 2010
- Ward, Carol. “Big mystery: What made us stand tall?” Mysteries of the Universe. 12 Nov. 1998. MSNBC. 12 Dec. 2010
- University Of California - Davis. "Why Humans Walk On Two Legs." ScienceDaily 20 July 2007. 13 December 2010