Siamese Twins are Becoming Common
Here in the Philippines, Siamese twins are becoming common. Many cases have been reported over the past 5 years.
According to wikipedia.org,
Conjoined twins are identical twins whose bodies are joined in utero. It is a rare phenomenon; it is estimated to range from 1 in 50,000 births to 1 in 200,000 births, with a somewhat higher incidence in Southwest Asia and Africa. Approximately half are stillborn, and a smaller fraction of pairs born alive have abnormalities incompatible with life. The overall survival rate for conjoined twins is approximately 25%.
About 70% to 75% of conjoined twin pairs are female.
Two contradicting theories exist to explain the origins of conjoined twins. The older and most generally accepted theory is fission, in which the fertilized egg splits partially. The second theory is fusion, in which a fertilized egg completely separates, but stem cells (which search for similar cells) find like-stem cells on the other twin and fuse the twins together.
Perhaps the most famous pair of conjoined twins was Chang and Eng Bunker (1811–1874), Chinese brothers born in Siam, now Thailand. They traveled with P.T. Barnum’s circus for many years and were billed as the Siamese Twins; due to their fame and the rarity of the condition, the term came to be used as a synonym for conjoined twins, although in recent years the term has fallen out of favor and is considered a pejorative term. Chang and Eng were joined by a band of flesh, cartilage, and their shared liver at the torso. In modern times, they could have been easily separated.
