Since 1976, the World Twin Congress has been held every summer. In 1986, more than a dozen countries and hundreds of pairs of twins attended. Interestingly, at each twin conference, the pair of most similar twins is chosen. There is also a "twin city" in the United States. More than two hundred years ago, in Columbus, Ohio, there was a twin sister who lived together and did business together. They died on the same day (September 25, 1827) and were buried in the same grave. In honor of the twin sisters, posterity named the city of Columbus "Twin Cities". But are the fates of twins in the world the same? No, the Indians of South America believed that the twins were the big brown bears at work, so they left the first and killed the second. In Nigeria, the twins suffered worse and both were killed.
According to statistics, there are more than 70 million twins in the world. A Librarian in the Soviet Union has been collecting information on twins at home and abroad from newspaper materials for twenty years. He collected data on twenty-eight cases of five children born in one child, all of whom were alive and well-developed. According to the Encyclopædia Britannica, there were twelve cases of six children born in one child in the last century; there were twenty-three cases of seven or eight twins in one child; and there were records of nine children in one child, only one case, that is, on June 13, 1971, someone in Australia gave birth to five boys and four girls, two of whom were born. There were three cases of decastals in the last century. On 17 September 1988, a woman in bern, Switzerland, gave birth to twelve babies in one litter, nine men and three women, and eight of them survived except for four of the lighter ones who had died. The woman, Kayla, was twenty-seven years old and she had become pregnant from a new drug. Due to the different regions and ethnic groups, the incidence of twins is also different; Japan is not as numerous as the mainland, while there are more countries in northern Europe such as Denmark, Norway, and Sweden than on the mainland. The birth rate of black twins in the United States far exceeds that of white Americans. The reason for this difference is not yet clear, but it is more consistent with genetic factors. According to statistics, the incidence of twins and multiples is 1: 77.9 times, triplets are 1: (77.9) 2, and quadruplets are 1: (77.9) 3; and so on, the more twins, the rarer, the more interesting people.
How do twins and multiples form? In the era when science was not developed, many people thought that the twins were caused by the father's excess semen. It was not until more than two hundred years ago, with the development of embryology, that people began to understand the study of twins from the genetics. It was only known from 1924 that there were two types of twins: one-egg twin and fraternal twin. An egg twin is the result of the division of one fertilized egg cell into two or more embryonic structures. Because they contain the same set of chromosomes and genes, the genetic material between the two is almost identical and communicative. So the twins look exactly the same.
Through the investigation, it was found that all twins who feel pain at the same time and can transmit information at the same time are almost all identical twins. Fraternal twins are two eggs and two sperm in the mother's body that make up two embryos. There are fewer genetic similarities between the two than the monovivial twins. Were the twins born because of the mother, or because of the father? For such a mystery, the current conclusion is more focused on the influence of the father. A Soviet expert on twins gave the example in her book: a man married a woman and gave birth to nine pairs of fraternal twins: the woman married for the second time and had six children, but none of them were twins. In the past, there was a report in foreign newspapers that a Ugandan policeman named Vamona Uangissu had married four wives at the same time at the age of thirty; ten years later, he had become the father of twenty-six children, twenty of whom were twins and six of whom were triplets. So why is the birth of twins closely related to the father? Experts study the process of fertilization of eggs. If a sperm is combined with an egg, it grows to be a twin. Some experts believe that the cause of twin formation is caused by a genetic function, because the enzyme released by sperm can change the lysis of the transparent membrane of egg cells, creating the possibility of more than one sperm penetrating the membrane of egg cells, resulting in twins or multiples. Of course, the results of the study are only the conclusions of some experts. But it is believed that the mystery of the twins will be finally solved with the efforts of scientists from all over the world.
It is not surprising that the twin siblings look very similar, even in height, weight, experience, hobbies, and occupations; what is even more strange is that there are black and white twins with very different skin colors and hair colors. Born in May 1978 in the UK, twin sisters had the same faces but very different skin tones, hair colours and eye colours. One was named Kelly, with white skin and blonde hair and blue eyes; the other was called Calais, but he was dark-skinned, with black hair and corny eyes. The sisters' father was a black British named Smith, and her mother was a white English named Patricia. After the birth of the black and white twin sisters, it aroused great interest from geneticists and gynecologists from all over the world. Experts believe that due to the extremely rare inequality of distribution when assigning genetic genes, Kelly is due to the dominance of her mother's genetic genes, while Calais is the father's genetic dominance in her. But in Wushan County, Sichuan Province, there is a twenty-six-year-old woman named He Shimei, who gave birth to three boys in one child, who developed well, but her face was very different: the eldest child was red-faced, the second child's face was black, and the third child's face was white-faced. What is the explanation for this? Twins are still a mystery?