Woolly mammoth diorama with museum worker. (Jonathan S. Blair/National Geographic/Getty Images)

Researchers say they have found evidence that the woolly mammoth may have mated with a much larger elephant species.

“We are talking about two very physically different species here,” researcher Hendrik Poinar, an evolutionary geneticist at McMaster University in Hamilton, Canada, told Live Science.

Researchers believe that woolly mammoths, who lived in the cold of the tundra, mated with Columbian mammoths, who preferred the more temperate regions of southern and central North America.

But the Columbians were much larger than woollies, with Columbian males reaching almost two times that of woolly males. And there are roughly one million years of separation between when the Columbian mammoth migrated into North America some 1.5 million years ago, and when the woolies arrived some 400,000 years ago.

So how and why did they find one another?

It’s likely that when glacial times got especially bitter cold, the woolly mammoths moved to more pleasant conditions southward, which is where they met the Columbian mammoths.

“Living African elephant species hybridize where their ranges overlap, with the bigger species out-competing the smaller for mates,” researcher Jacob Enk, a graduate student in the McMaster Ancient DNA Center, told Live Science.

When the mammoths mated, bigger was always better. “It reminds me a bit of high-school days — the larger males are more successful at meeting women across the dance floor than the rest of us,” Poinar said.

The hybrid offspring of the two were perfectly fertile.

Poinar and his colleagues made their findings while analyzing DNA retrieved from the tusks, bone, and teeth of 11,000-year-old Columbian mammoth specimens.

It’s then they realized the mitochondrial genome of the Columbian mammoth was nearly indiscernible from its woolly counterparts.

“At first I thought, ... ‘there's contamination of some sort,’” Poinar said. But the overlap was too great — they had found a hybrid.

Woolly mammoths roamed the planet for more than a million years, ranging from Europe to Asia to North America.  Nearly all these lumbering beasts disappeared from Siberia about 10,000 years ago, although dwarf mammoths survived until 3,700 years ago.