Doubly Interesting
Sunday
Globally, about 1.2% of live deliveries are twins. This number has increased dramatically in the last century, both due to improved fertility treatments, and because twins are more likely with older mothers, who are having more children these days.
Monday
Identical twins look alike because they have the same genetic info from a single fertilized egg which splits in two. Fraternal twins come from two eggs fertilized by two sperm, so genetically, they have no more in common than any other two siblings, despite arriving together. Fraternal twins are about twice as common as identical.
Tuesday
Global mythology is packed with twins, particularly Greek and Roman mythology. After all, it was twin brothers Remus and Romulus who founded Rome, and we still see the Greek twins Castor and Pollux in the night sky within the Gemini constellation.
Wednesday
Since people traveling near the speed of light experience time more slowly relative to the slower-moving, the “twins paradox” describes a situation where one twin leaves Earth to travel near the speed of light, to find upon returning that her twin has aged more than herself, despite both starting at exactly the same age. Because of their real-life space travels, twin NASA astronauts Mark and Scott Kelly are about 0.01 sec different in age.
Thursday
There is no genetic predisposition to having identical twins, since they come from an egg which splits randomly. However, fraternal twins come from multiple eggs, so women with a gene for hyperovulation, or releasing multiple eggs per cycle, are more likely to have fraternal twins. As such, fraternal twins can run in families.
Friday
The term “Siamese twins” originated with conjoined twins Chang and Eng Bunker, born in 1811 in Thailand (then known as Siam). After traveling with the circus and becoming known worldwide, they settled in the US, married sisters and became farmers who fathered 21 children between them.
Saturday
Some types of “twins” really aren’t. The term “Irish twins” refers to children born within 12 months of each other, and is a 19th century American idiom referring to Irish immigrant families who often had many children born very close together. The similar “Dutch twins” refers to to children born between 12 and 18 months of each other.