Are there more same-sex SS than opposite-sex OS pairs among dizygotic twins? However, recent research on the sex-specific nature of breastmilk suggests that OS twins might be at a developmental disadvantage relative to SS twins. There may therefore be evolutionary selection for the tendency to have SS twins and against the tendency to have OS twins. We performed a one-sample t -test of the proportion of SS dizygotic twins against the theoretical null value of 0.
Can Identical Twins Be Different Sexes?
Can Identical Twins Be Different Sexes?
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Types of Twins
K ath and Chris Dent are both well-travelled and like keeping fit. They enjoy similar music and have compatible political and religious views. They are both 59, have great fun together and sound like a perfect match. There is no chance of them getting together, however, because they are twins. Being in their company is rather like spending time with a married couple who have been together for years.
People are fascinated by twins, and thanks in large part to advances in fertility science, there are more twins than almost any other time in history. Identical and fraternal twins are the most common, but there are also several other rare types. Read on to learn more about twins.
A portion of this was filmed using a tripod.
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