You’ve probably heard that whales share a common ancestor with hippos or that whales evolved from land mammals in the distant past. But what about their more recent natural history? How did Earth’s oceans end up with the 84 different species of whales we have today, with species as varied as the Humpback Whale and the Pilot Whale? The ancestor of all modern whales appeared in the oceans about 35 million years ago, and just 10 million years later, all the whale forms we know today had differentiated, an explosive rate of adaptation and change. Molecular studies and computer models have been used to explore just how 1 species turned into hundreds, and it turns out Whales simply filled every ecological niche available, evolving into small, medium, and large sizes, some with baleen, some with teeth, all still maintaining distinctly mammalian characteristics like live births and breathing air.