165. The Science of Twins

Between 1980 and 2009, the rate of twinning in the US increased by 76%, and this trend is seen across the world. Twins can be either fraternal where two eggs are fertilized at the same time, or identical where one fertilized egg splits in two. Both of these offer huge opportunities for scientists to learn about genetic traits and environmental impacts on development. Luke explains what we've learned from twin studies and why they're so useful.