You would think that giraffes, the tallest land animals in the world, would be hard to overlook.

Yet, for centuries scientists may have missed a fundamental fact about these long-necked creatures: They aren’t one species, but rather four distinct ones.

“The genetic differences between giraffes is so large that we have to in fact describe four new species,” said Axel Janke, a geneticist from the Senckenberg Biodiversity and Climate Research Center in Frankfurt. “Some of the differences were as large or larger than the differences between brown bears and polar bears.”

Dr. Janke, along with Julian Fennessy from the Giraffe Conservation Foundation in Namibia and their colleagues, tested the DNA of nearly 200 giraffes from across Africa. They found genetic mutations that were present in certain groups and absent in others. The differences in mutation patterns, they said, were strong enough to classify the groups as distinct species. In some cases subspecies of giraffe were upgraded to being full-blown species. The team published its results Thursday in the journal Current Biology.