Pingelap is an atoll in the Pacific Ocean, part of Pohnpei State of the Federated States of Micronesia, consisting of three islands: Pingelap Island, Sukoru and Daekae, linked by a reef system and surrounding a central lagoon, although only Pingelap Island is inhabited. The entire system has a land area of 1.8 km² (455 acres) at high-tide, and is less than 2.5 miles (4.0 km) at its widest point. The atoll has its own language, Pingelapese, spoken by most of the atoll's 250 residents.
The atoll was seized by Japan in October 1914, following the start of World War I, and the southern part of Pingelap Island was occupied by Japan during hostilities in the Pacific Ocean theater of World War II for a supply base, and was attacked by Allied Forces. The presence of foreign troops on the island led to the introduction of a number of infectious diseases, including gonorrhoea, tuberculosis and dysentery, which reduced the population from its pre-war level of around 1000 to 800 and decreased the fertility rate significantly.
Historically, the atoll was ruled by a paramount chief known as the nahnmariki; a hereditary title that granted certain land rights to its holder. This system remained in place during Japanese rule, although the title was renamed "Island Magistrate". However, with the arrival of the U.S. Navy in 1945, a democratically-elected system was set up alongside the traditional system, which gradually weakened in power. Universal primary education was provided for Pingelapese children and a limited health care scheme was set up to eradicate the diseases introduced during the war.
During the 1960s, the Peace Corps and U.S. Air Force settled on the main island, constructing a missile watching station in the northeast of the island and a pier, with work beginning in 1978 on an airstrip, jutting into the lagoon, on the main island. The runway was finished in 1982, and currently between 2 and 3 planes per day fly to and from the atoll, operated by Caroline Islands Air.
Typhoon Lengkieki and Achromatopsia
In 1775, a catastrophic typhoon, Typhoon Liengkieki, swept through the island, killing 90% of the inhabitants and leaving only approximately 20 people. It is believed that one of the survivors, namely Nanmwarki Mwanenihsed (the ruler at that time), was a carrier for complete achromatopsia (known on the island as maskun, meaning literally "not see" in Pingelapese), a recessive genetic disorder that causes total color-blindness in sufferers. All Achromats on this island nowadays can trace their ancestry to this male survivor. However, the achromatopsia disorder did not appear until the fourth generation after the typhoon, where 2.70% of the Pingelapese were affected. By generation 6, the incidence rose to approximately 4.92%. These statistics can be accounted for by inbreeding and two related concepts, the bottleneck effect and genetic drift. In the case of achromatopsia on the Pingelap Island, the achromatopsia mutation fluctuated immensely from generation 3 to generation 4 under an extreme form of genetic drift. This type of genetic drift occurs only when the population is extremely small (20 survivors after typhoon) and is also known as the founder effect. Of course, both concepts occur due to inbreeding. To be able to recover the atoll's population as fast as possible, the survivors must undergo a substantial amount of inbreeding in the early generations. Because relatives share many of the same alleles inherited from their common ancestor, there is a high probability that the offspring of two related parents will inherit an identical allele from each parent. Since achromatopsia is an autosomal recessive disorder, inbreeding between the descendants of Nahnmwarki Mwanenised (the typhoon survivor and achromatopsia carrier) will result in an increased recessive allele frequency.
As of today, the atoll is still of particular interest to geneticists because of the high occurrence of achromatopsia; due to the small gene pool and rapid population growth, the disorder is now prevalent in almost 10% of the population, with a further 30% being unaffected carriers (by comparison, in the United States, only 1 in 33,000, or 0.003%, are affected), leading neurologist Oliver Sacks to write his 1997 book The Island of the Colorblind.
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