Have you ever wondered why you look the way you do?  Do you ever think about what you are going to look like in five years, or in 25 years?  When you were born, you didn't look the way you do today.  In fact, when you were born, you probably looked like a lot of other babies: small, a bit round, no hair, no teeth and little chubby arms and legs.  Although we start out looking like other babies, we all change and grow to look different, as we get older.  Some people grow tall, and some do not.  Some people's feet are bigger than others.  Some people need glasses, and others see clearly.  Some people have skin that is smooth, and some have skin that is wrinkled or freckled.  Some people seem to have strong muscles and others look like they have no muscles at all.  We all look very different.  The reason for our differences involves both what we were born with and what happens to us after we are born.

When I grow up I want to look just like you.
User:MultipleParent, CC BY-SA 3.0 , via Wikimedia Commons

Some things about us are set before we are born.  When a mother and father have a child, they give things like eye color and hair color to their child.  Traits are the parts of us, and all living things, that we get from our parents that make up what we look like.  Traits are things like eye color, hair color, height, and whether our second toe is longer than our big toe.  Let's say a mother and father both have red hair.  Their child will most likely have red hair too.  Even if their child is born with no hair at all, you can make a good guess that the hair that will grow will be red because his or her hair color is already decided.  It is a trait that the child's parents passed along to their baby. 

No, not him, the one with the red hair.
Eddy Van 3000, CC BY-SA 2.0 , via Wikimedia Commons

Some things about us, though, are shaped by what happens after we are born.  Imagine twin girls who are born with the same exact traits: same hair, same eyes, and same size.  As they grow up together they will look alike, and most likely will sound alike.  If they dress alike, too, it could be very hard to tell them apart.  Now think about what would happen if those twins spend their childhood living in two different homes.  One home might be in a very cold place and the other in a warm area.  Then these girls would most likely wear different clothes, play different sports and eat different foods.  They might have been born with the trait of having crooked teeth, but if one twin gets braces and the other does not, their smiles will end up looking very different.  When they become adults, even though they were born with the same traits, the way they grew up may have changed them in some ways.  Environmental influences are things in the world around us that change what we need and the way we grow.  Even if two people start out almost the same, like twins, where and how they live can change the way they look as they grow up. 

Chocolate chip, a very good natured cookie.
Basheer Tome, CC BY 2.0 , via Wikimedia Commons

If twins who are born with many of the same traits can grow up to look different, then what is it that really makes us who we are?   Believe it or not, scientists have been talking about this question for hundreds of years.  Some believe that it is mostly the traits that we get from our parents that decide who we are.  They call this our nature, or all the parts we get from our parents that make up who we are when we are born.  Think about making chocolate chip cookies.  You need sugar, flour, butter, eggs and chocolate chips.  The nature of the chocolate chip cookie comes from those ingredients that have been mixed together.  If you use raisins instead of chocolate chips, they would no longer be chocolate chip cookies.  They would be raisin cookies.  Your nature is all of your body's ingredients put together.  They are the parts and pieces of you that you have when you enter the world.  If you change one of them, like the chocolate chips and the raisins, then you would be different too.

However, we know from our look at those twins that a person's nature can be changed by where they live and the way they grow up.  Nurture is the way the world around us acts upon us and changes us as we live and grow.  Over the years, many people have believed that this is what really decides who we are, no matter what we have in us when we are born.  They thought that we could raise a child to become just what we wanted him or her to be. 

A square chocolate chip cookie? That would be a brownie.
Heather, CC BY 2.0 , via Wikimedia Commons

Let's go back to that cookie.  We know the nature of the cookie, or all the stuff that goes into it, but that's only the first part of what your cookie will be like.  Once you have everything mixed together, you shape the cookie dough into balls, put them on the baking sheet and place it in the oven.  The heat of the oven bakes the dough, and the cookie becomes flat and round.  Now, if you put that cookie dough into a square-shaped pan, it would not come out round.  The shape of the pan, or the cookie's environment, changes the way the cookie "grows up."  You get two different looking chocolate chip cookies, even though all the ingredients are the same.  Now make believe that you are the cookie.  Your nature might say that your feet will grow to be a certain size, but if you grow up wearing shoes that are too small for you, your feet might not reach their full size.  You can change the way your feet grow just by wearing the wrong size shoe!

As these two ideas of nature and nurture have been studied over the years, many people have come to agree that both are very important to how we grow and who we become.  What we get from our parents forms the beginning of what we are going to look like and act like.  It has a hand in how we look at the world and how the world looks at us.  However, the place where we live and the way we grow up matters very much as well.  What we go through in our lives and the way the world changes us plays a big part in how we become who we are.