Your family tree more than likely contains approximately as many male ancestors as it does female ancestors. At first glance, it might seem to have more of one gender than the other. In those cases, it is easy to see why a family with an abundance of boys would celebrate the birth of a baby girl.
The Underdahl family has what they lightheartedly refer to as a “curse”. Their family tree is heavily populated by boys, and has been that way for 102 years. This was discovered by Conrad Underdahl who researched his family history back for several generations. He realized that after a certain point, there weren’t any female children in the family.
Conrad Underdahl is the father of Scott Underdahl. Scott and his wife Ashton were expecting a baby. That baby turned out to be a girl – the first one in the family for more than 100 years. Obviously, the family is excited that the “curse” had been broken.
What are the odds of having a baby boy (or a baby girl)? Part of the answer to that question relies upon genetics. All humans have sex chromosomes. Men usually have one X chromosome and one Y chromosome. Women usually have two X chromosomes. Most men produce sperm, and most women produce eggs (during the years between when they start menstruating and when they reach menopause).
The sperm determines whether a baby will be a boy or a girl. Each sperm is made with one of the sex chromosomes. Every egg contains one X chromosome. The sperm that manages to fertilize the egg either has an X chromosome or a Y chromosome (but not both). Two X chromosomes mean the baby will be a girl. One X chromosome and one Y chromosome mean the baby will be a boy.
King Henry VII divorced his first wife, Katherine of Aragon, because she failed to produce a male heir. He had his second wife, Anne Boleyn, beheaded after she failed to produce a male heir. King Henry VII could not have known what we know today about genetics. It is the sperm that determines whether the baby will be a girl or a boy – not the egg.
The odds of having a boy or a girl are similar to the odds of flipping a coin and having it turn up “heads”. That’s not exactly a perfect explanation, though.
Pew Research Center points out that, historically, there have been 105 boys born for every 100 girls worldwide. The most recent data comes from 2011, which said that the sex ratio at birth is now 107 boys born for every 100 girls.
Image by Jonathan Rolande on Flickr.
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