Why do dogs have four legs?

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Dogs belong to a special group of animals called “mammals.” So do cats, rats, bats, elephants, kangaroos and hippos!  Most mammals have four legs.  They need these legs to move and they also need them to balance!

Think of a dinner table.  Most tables have four legs, so they’re nice and sturdy to eat on.  Now imagine the table with only three legs.  It might get a little wobbly, but as long as you don’t push on the wrong part, it will stand.  Imagine the table with only two legs or one leg.  Now it just tips over!  Four legs give dogs the support they need to stand and move without falling.

Having four legs also helps dogs run very quickly. This way in the wild, they can catch food.  Four legs can move faster than just two!  (At least for dogs.)

by   (whyzz writer)
  • Exploration

    Breaking the Mammal Mold! 

    Some mammals don’t walk on four legs, and you’re really familiar with one of these mammals: People!  It might be strange to think of, but among most mammals, we’re the weird ones! 

    A long time ago (millions of years!) people used to walk on four legs too.  In fact, we still do when we’re babies.  When we’re very young, we don’t have the balance we need to stand up on two legs.  

    Why did we decide to use only two legs and not four? Scientists have come up with a few possible reasons. One is that people are very smart, and we may have wanted to keep our hands free so we could use tools!  We also may have learned to stand up so we could walk through water in some rivers and still keep our heads dry so we could breathe.  Some chimpanzees do the same thing!  

    Imagine if you lived life walking around on four legs. You can even try it for a few minutes! What are some of the difficulties that you’ll face?  It might be tough trying to do things without using your hands. Also, you’ll get tired quickly because over thousands of years, people’s bodies have gotten used to walking on two legs. We’re built to stand up.  Most other animals could certainly outrun us if we raced while running on four legs! 
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