If you’ve ever seen a vulture at mealtime, you’ve probably thought, “…Why?” Why would any animal intentionally eat rotting meat? We don’t know why, and the vulture’s philosophical motivations remain a mystery. But an examination of the bird's genome has reveals the how: an ironclad gut and a super-strong immune system.

Ornithologists have long suspected that vultures have super-strong immune systems, but they haven’t had proof—until now. A paper published today in the journal Genome Biology reports two important findings in the vulture’s genes.

Scientists divide vultures into two genetic groups. Old World vultures hail from Europe, Asia, and Africa, and New World vulture species originated in North and South America. The two groups went their separate ways around 60 million years ago.

With a wingspan that can reach nine and half feet, the cinereous vulture (Aegypius monachus) is one of the biggest birds of prey in the world. This Old World vulture is a familiar figure in the skies above Europe and Asia, and has made itself quite unpopular by preying on farmers’ livestock.

Researchers from 14 institutions collaborated to sequence the genome of the cinereous vulture. They found that genetic variations help make stomach acids that allow the vulture’s gut to break down chunks of carcass. They also discovered variations in the genes related to fighting off infection.

In a press release, lead author Jong Bhak of South Korea’s Ulsan National Institute of Science and Technology said the findings could reach far beyond birds:

"Understanding the genetic make-up of extreme life forms has potential for improving human health. The immune system genes we’ve identified could be useful targets in humans for protection against infection."

The scientists' analysis teaches us more about these birds than just this finding about their immune systems. The research team compared the vulture’s genome to that of the bald eagle and found that the birds were more closely related than previously thought. Genetic analysis suggested that American eagle and Old World vulture species split 18 million years ago—far more recently than the Old World and New World vultures.

Geneticist and co-author Yun Sung Cho, also from the Ulsan National Institute of Science and Technology, commented in the press release that the cinereous vulture seems to be “somewhere in between a vulture and an eagle.” It might be more accurate, he said, to call the bird a "cinereous eagle."

All photographs courtesy of Woon Kee Paek