With billions of people in the world and the thousands of genes each person has, it’s hard to believe that any two people are exactly alike … unless those people are twins.
Identical, or monozygotic, twins develop from a single egg and sperm combination that splits a few days after conception. Their DNA comes from the same source, making them share on average 100 percent of their genes. The odds of having identical twins are 1 in 240 pregnancies.
Fraternal, or dizygotic, twins are far more common, occurring once in every 60 pregnancies. They form when two separate eggs are fertilized by separate sperm in one ovulation cycle. They share a unique combination — about 50/50 — of genes from both parent.
But even if twins share similar genes, they can be totally different from each other in personality and interests. The environment has a big impact on how people act and behave. Even though most twins grow up in the same environment, the way they are treated or their experiences might set them apart from each other.
Not all twins are exactly alike
Physics teacher Jeff McManus knows what it’s like to grow up with an identical twin who was very different from him.
“Our interests have always been very diverse,” McManus said. “I liked sports a lot more than he did, while he liked to play the piano. He was into cars, while I couldn’t care less about them.”
Even now that they are older, McManus still sees some differences among the growing similarities. “We are both teachers, but he teaches elementary school music and I teach high school science. I am married with four children and he’s a happy bachelor,” McManus said.
Juniors Kristen and Kevin Menke, fraternal twins who were the first twins born in Dayton in 1995, can relate. Even though they share an interest in swimming, they find their other interests take them in opposite directions.
“I’m the smart one and I like creative things, and Kevin likes sports,” Kristen said.
Junior fraternal twins Olivia and Kate Teleha sometimes say it’s hard to find similar interests or personality traits.
“People are surprised that we are twins because we are so different,” said Kate. “Olivia is very bubbly and constantly laughing. She is very loyal to those she has known for a long time.”
But Olivia says Kate is the more outgoing twin. “She loves to meet new people and is much more comfortable talking with strangers than I am,” said Olivia. “She won’t hide what she thinks of people.”
For the freshmen Fornes triplets, their personalities are reflected in their birth order. Brooke is the oldest by a few minutes and Taylor is the youngest with Margo in the middle.
Brooke is known as the smartest and most responsible and the leader of the group. “I’m the one my parents trust,” Brooke jokes.
Taylor is the “baby” of the family and the troublemaker, while Margo is in the middle of Brooke and Taylor personality-wise. “She has the best of both worlds,” said Brooke.
Even though the Fornes are triplets, people sometimes have a hard time believing it. Taylor and Margo are identical, while Brooke is fraternal to them both (and is shorter with a different hair color). This happens when two separate eggs are released and one splits after it is fertilized.
Usually people think Margo and Taylor are twins and Brooke is a friend of theirs, leaving Brooke with a feeling of being left out. “Sometimes we just agree with them because it is hard to explain the whole story,” said Brooke.
Which twin are you again?
Of course, every identical twin or triplet has to deal with people getting them confused. “When we are together, it is obvious something is different,” said McManus about his twin, Chris. “It’s when we aren’t together that people are more likely to get us mixed up.”
When Chris comes down from Columbus for the Labor Day parade, “students who have only known me for a couple of weeks will assume it is me when they see him,” said McManus.
When they were younger, people would also get them confused because they dressed the same. “Eventually, I had a shirt that said ‘I’m not Chris’ and he had a shirt that said ‘I’m not Jeff,'” McManus said.
Genetics may play a role
According to Stanford University geneticist Karen Fitch, identical twins happen by sheer chance but fraternal twins run in families on the mother’s side.
Since identical twins do not run in families, it is extremely rare to have two sets of identical twins. However, that is exactly what happened to the McManus family. “I have older brothers who are identical twins as well,” McManus said. “I like to think we are one in a million.”
While they may not be one in a million, the chances of having two sets of identical twins are 1 in 70,000, and while the McManus family has two sets of twins in their family, none of the twins has twins as children. Some think that twins skip a generation, but this hasn’t been scientifically proven.
Being a twin has its ups and downs
Many positives and negatives come with being a twin or triplet.
“I like having someone my age around the house and someone that can help me with homework,” said Kevin Menke.
When McManus was younger, he enjoyed the socialization aspect. “I loved having a twin growing up; there was always someone to play with,” he said. However, he didn’t like always having to share a birthday. “It was never your day.”
For the Fornes twins, it’s more about wanting to be their own person.
“Being compared to each other is definitely a downfall,” Margo said. “You want your own identity. Some people ask, ‘What is it like to be a triplet?’ and I respond, ‘What is it like to not be a triplet?’ People think it is so weird, but it feels normal to us.”