In 2010, geneticists at the University of Colorado, Boulder compared DNA samples from eight hammerhead species in an attempt to map out the family's evolutionary history. The molecular evidence suggested that the hammerheads started to diversify around 20 million years ago. The fossil record tells us sharks have existed for at least 420 million years—so if the University of Colorado team is correct, hammerheads are relative newcomers on the world stage. What did the earliest hammerheads look like? According to the researchers, these were probably large-bodied animals. They also argued that today's modestly-sized bonnethead and winghead sharks independently evolved from big ancestors.