Evolution depends on random mutations to slowly change species, but the process gets a turbo-charged boost when related species interbreed. It happens more often than you might think- just ask the minority of your ancestors who are Neanderthal, although they wouldn't answer. A new study by evolutionary geneticists from several universities tells of findings from the sequenced genomes of woolly mammoths, a Columbian mammoth, straight-tusked elephants, American mastodons, and three living elephant species. What they found was clear evidence of interbreeding among extinct species, but not among living species.
For example, the researchers learned that the ancient Straight-tusked elephant—an extinct species that stomped around Europe between 780,000 and 50,000 years ago—was a hybrid species, with portions of its DNA being similar to an ancient African elephant, the Woolly Mammoth, and Forest elephants, the latter of which are still around today. They also uncovered further evidence to support the suggestion that two species of mammoths—the Columbian and Woolly Mammoths—interbred. This idea was first proposed by Poinar in 2011. Despite their different habitats and sizes, these creatures likely ran into each other near glacial boundaries and in more temperate regions of North America. Indeed, it shouldn’t come as a surprise that these ancient elephants frequently bumped into each other; for a time, mammoths had a territory that extended from modern-day Portugal and Spain all the way to the US East Coast.
The ability to sequence all those extinct genomes is a story in itself. Read more about the study at Gizmodo.
Some new things I learned from fact-checking this article: mastodons are not considered elephants. Here is the family tree. The article mentions the two extant species of elephant, but they mean two species of African elephants; there's also the Asian elephant. There are an astonishing number of elephant species when you include the extinct ones.