Imagine being surrounded by a colorful world but not being able to perceive it in its full glory. As sad as that sounds, this is a reality for people who are colorblind. Not everyone has the perfect color vision, but can you imagine an island where 10% of the population is genuinely and completely colorblind? Pingelap, a small atoll in the Pacific, has an unusually high number of colorblind residents. Moreover, it is not the typical colorblindness, one where you find it difficult to distinguish between red and green or blue and yellow. The residents of this tiny island can almost only see the world in black and white.
Situated in the Pacific Ocean, Pingelap Atoll is part of Pohnpei State. It consists of three islands, but Pingelap is the only one inhabited. The atoll covers a 455-acre land area, and the widest point is less than 4 km. Pingelap has a population of 250 and its own language called “Pingelapese.” Most of the island’s residents speak this native language. The island has a tropical climate, and it enjoys warm and even temperatures all through the year. Precipitation usually remains high, and the island receives heavy rainfall all year round.
In 1775, a deadly typhoon called “Lengkieki” ravaged Pingelap and killed most of the islanders. After the storm and the famine that followed, the island had a population of only 20. One of the survivors, who was also a ruler at the time, is thought to have been the carrier of the gene that is now known as “CNGB3.” This gene resides in Chromosome 8 and is responsible for one of the most common forms of rod monochromatism. This recessive genetic disorder is known for causing total color blindness or complete achromatopsia.
It is believed that cultural and geographic isolationism led to generations of inbreeding among the survivors who repopulated the island. Interestingly, the carrier of the gene did not have the disorder. Being an autosomal recessive disorder, achromatopsia is likely to occur as a result of recessive allele frequency. That is why the signs of achromatopsia did not show up until the fourth generation that came after the typhoon. By the sixth generation, 4.9% of the population had the disorder.
The colorblindness occurred as a result of inbreeding and the “founder effect,” which is why all the colorblind people of the island can trace their ancestry back to the ruler who originally had the CNGB3 gene. Moreover, people who have this disorder have trouble seeing in sunlight. However, their night vision is much stronger than people who do not have achromatopsia, and they can easily spot faint light.
After over 30 years of research into Pingelap and its colorblind population, scientists were finally able to find the answer in the year 2000. Geneticists Irene Hussels Maumenee and Olof Sundin of the Johns Hopkins University School of Medicine tested the DNA of 32 islanders, only 50% of whom were colorblind. After several tests and studies, they were finally able to track the gene responsible for the condition. Their report was published in Nature Genetics.
To this day, Pingelap Atoll is a topic of interest among geneticists around the world. The combination of a small gene pool and rapid growth in population has made achromatopsia unusually common on the island. Nearly 10% of the island’s population is colorblind. In the United States, only 0.003% or 1 in 33,000 people are colorblind.