Two-headed snakes are twins with one egg. During the development process, due to the influence of environmental and other factors, deformed eggs were formed. It may also be because the snake's genes (the part that controls the head) are unstable and prone to mutation, which is a mutant snake.
It can be preliminarily concluded that the two-headed snakes are monoovous twins. During the development process, due to the influence of environmental and other factors, deformed fetuses were formed. Excessive use of chemicals, pesticides, fertilizers, etc. that pollutes the environment may cause this genetic mutation.
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A case of a two-headed snake
1. In early July 2008, a resident of Maine in the United States discovered a two-headed snake. This snake has two heads, but only one set of body and other organs.
2. On October 15, 2009, Qiu Zongbao, a farmer in Bazhou, China, discovered a two-headed snake under the wall of an old house in the countryside.
3. On July 6, 2015, a two-headed Chinese cobra, also known as the Zhoushan cobra, appeared in the snake garden of Nanning Zoo. In addition to the stomach and other digestive and reproductive systems, this two-headed snake has its own brain, heart, eyes, tongue and other organs, which are separated six centimeters from the snake's head to the body.
Reference source; Baidu Encyclopedia-Two-Headed Snake