Aside from their way of life, customs, and traditions, there isn’t much to physically distinguish them from regular folk. But there’s an Indonesian tribe on the island of Buton, whose people have one distinct feature that sets them apart – blue eyes. Meet the Buton Tribe.

Indonesia is a vast archipelago with over 350 dialects and subcultures. With a size of 1,700 square miles, Buton Island is one of Indonesia’s larger islands. The Buton people are from Indonesia’s 19th largest island, Buton Island, which is located in the southeast Sulawesi region of Indonesia.

Its population totals just under 450,000 people of which many live in small, isolated tribes. The majority of the island is covered with rainforest.

After recent photos of the tribe, taken by geologist and photographer Korchnoi Pasaribu, went viral on social media, many have been wondering how it’s even possible for this one group of people to have naturally blue eyes, especially considering the fact that most Asians have brown eyes.

It turns out that the tribe developed these piercing blue eyes as a result of a rare genetic disorder called Waardenburg syndrome.

According to the U.S. National Library of Medicine, Waardenburg syndrome is a group of genetic conditions that can cause hearing loss, and changes in pigmentation of the hair, skin, and eyes. But before you start thinking that every single person in the Buton tribe has blue eyes, think again.

According to Discover ASEAN, the Butonese people mostly have normal brown eyes, but a small sub-group has developed blue eyes. And even then, some only have one eye blue, while the other stays brown.

The Waardenburg syndrome is a hereditary genetic mutation that is estimated to be present in some form in 1 in 42,000 people. In addition to its sometimes startling effect on eye pigmentation, including causing eyes of different colours, it can also lead to a loss of hearing.

According to Daily Mail, Mashable SE Asia