1. In addition, fertility medications have produced more twins. 2. Twins and women who bore them would be less likely to survive than singletons and thus less likely to pass on a tendency to produce fraternal twins. 3. A proper division would produce twins. 4. Fraternal twins are produced when the mother releases more than one egg and both are fertilized. 5. A rare Burmese bear has produced twins to become the first bear to give birth in captivity in Vietnam, the Vietnam News Agency reported Friday. |