Evolution At Work

"Twins have been rare in human history and for that reason can seem special. Many cultures associate twins with health and vitality, while others see them as a philosophical reminder of the duality of life and death, good and evil. Some famous twins are credited with the birth of nations, others are described as deities.

"Our recent research suggests that twins were actually the norm much further back in primate evolution, rather than an unusual occurrence worthy of note. Despite the fact that almost all primates today, including people, usually give birth to just one baby, our most recent common ancestor, which roamed North America about 60 million years ago, likely gave birth to twins as the standard.

"We have been researching the evolution of primate litter size – how many babies grow during each pregnancy – for the past several years. To study mammal evolution and reproductive life history, we use skeletal collections, both fossil and recently living.

"In addition to being an anthropologist, one of us (Tesla) is the mother of twin girls. That’s led to a personal and not just scientific interest in this topic: When did twin pregnancies become uncommon?"

Click on this link for more: