The great white shark isn't descended from megatooth sharks such as the extinct Carcharocles megalodon - the largest carnivorous shark that ever lived - as many believed.
Instead, it seems to be descended from the comparatively benevolent broad-toothed mako sharks, with University of Florida researchers having now named and described an ancient intermediate form of the white shark, Carcharodon hubbelli.
The team has also recalibrated the dates of an excavation site in Peru, and concluded that the new species was about two million years older than previously believed.
"That two-million-year pushback is pretty significant, because in the evolutionary history of white sharks, that puts this species in a more appropriate time category to be ancestral or kind of an intermediate form of white shark," says former UF graduate student Dana Ehret.
Scientists extracted more accurate age estimates from mollusk shells to determine that the shark species was from the late Miocene, about 6.5 million years ago, rather than the early Pliocene, about 4.5 million years ago.
They determined that Hubbell's white shark was related to ancient broad-toothed mako sharks by comparing the physical shapes of different shark teeth. While modern white sharks have serrations on their teeth for consuming marine mammals, mako sharks don't, asthey primarily feed on fish.
Hubbell's white shark has coarse serrations, indicating a transition from broad-toothed mako sharks to modern white sharks.
"We can look at white sharks today a little bit differently ecologically if we know that they come from a mako shark ancestor," says Ehret.