Identical twins look so much alike because they share the same genetic material – DNA. Yet, if you look closely, you will see differences, in height, or in the number of freckles, etc. To answer why, let’s compare identical twins to apple pies made from the same recipe. When you take the pies out of the stove, each pie will turn out a little different even though they have exactly the same ingredients. Differences in the environment make it impossible for each apple pie to be exactly the same – perhaps the stove was a little hotter while one was cooking, or they were removed from the oven at different times, etc.
So identical twins are like two pies made from the same recipe. They are more similar than they are different, yet they will always have some physical differences due to differences in their environment.
You may have heard the phrase “nature vs. nurture” before, but what exactly does it mean? Two things are responsible for making us who we are: Nature and Nurture. Our genes (nature) are important, but they are not the whole story. Our environment (nurture) also plays a big role.
By environment we mean things like what we eat, how much we sleep, whether get sick and when illness occurs. These are things that happen during our life that also have an impact on who we are and what we look like.
Some identical twins can have different heights and weights. This is because height and weight are not only controlled by our DNA, but also by what we eat, illness and other environmental factors. And differences in diet can start before twins are even born! When the twins are growing inside the uterus, there can be differences in how well they connect to the placenta. This can mean one twin starts getting more to eat even before they take their first breath.
Another physical difference between identical twins is their fingerprints. The fingerprints of identical twins do look more similar than the fingerprints of non-twins. But they are not exactly the same. They have differences that a fingerprint expert can use to tell them apart. This is because environmental differences like how the hand of the fetus touches the amniotic sac also affect fingerprints.
So now we know why identical twins can be different heights. This means height can’t be controlled by genes alone, because identical twins have the same genes. Therefore, height must be part nature and part nurture. On the other hand, identical twins almost always have the same eye color. So eye color must be mostly nature.
Many things seem to be controlled by a little of both. This means no matter how similar two people’s DNA is, each will always be unique.
For more information, check out these articles:
Growth Charts
What Happens When
Growing Up as a Boy
Growing Up as a Girl
Learn About Height
Posted 10-2-06
