Around 1 in 250 pregnancies result in identical or “monozygotic” twins, but the mechanism behind monozygotic twinning has remained elusive, partly because the phenomenon is so rare and partly due to ...

Fascination with twins and what twin studies tell us about human nature is universal. There is no question that behavioral and medical science advances have happened largely because twins yield a ...

Twins are pretty rare, accounting for just 3% of births in the U.S. these days. But new research shows that for primates 60 million years ago, giving birth to twins was the norm. When you purchase ...