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9 years ago Coconut germinating on Black Sand Beach, Island of Hawaii The coconut palm thrives on sandy soils and is highly tolerant of salinity. It prefers areas with abundant sunlight and regular rainfall (1500 mm to 2500 mm annually), which makes colonizing shorelines of the tropics relatively straightforward.[45] Coconuts also need high humidity (70–80%+) for optimum growth, which is why they are rarely seen in areas with low humidity, like the southeastern Mediterranean or Andalusia (Spain), even where temperatures are high enough (regularly above 24 °C or 75.2 °F). However, they can be found in humid areas with low annual precipitation such as in Karachi, Pakistan, which receives only about 250 mm (9.84 in) of rainfall per year, but is consistently warm and humid.
The origin of the plant is the subject of debate.[26][27][28] O.F. Cook was one of the earliest modern researchers to draw conclusions about the location of origin of Cocos nucifera based on its current-day worldwide distribution.[29] He hypothesized that the coconut originated in the Americas, based on his belief that American coconut populations predated European contact and because he considered pan-tropical distribution by ocean currents improbable. Thor Heyerdahl later used this hypothesis of the American origin of the coconut to support his theory that the Pacific Islanders originated in South America.[30] However, more evidence exists for an Indo-Pacific origin either around Melanesia and Malesia or the Indian Ocean.[26][27][28] The oldest fossils known of the modern coconut dating from the Eocene period from around 37 to 55 million years ago were found in Australia and India. However, older palm fossils such as some of nipa fruit have been found in the Americas.[28] Since 1978, the work on tracing the probable origin and dispersal of Cocos nucifera[31] has only recently been augmented by a publication on the germination rate of the coconut seednut [32] and another on the importance of the coral atoll ecosystem.[33] Briefly, the coconut originated in the coral atoll ecosystem - without human intervention - and required a thick husk and slow germination to survive and disperse.
Domestication[edit] Coconuts could not reach inland locations without human intervention (to carry seednuts, plant seedlings, etc.) and it was early germination on the palm (vivipary) that was important,[34] rather than increasing the number or size of the edible parts of a fruit that was already large enough. Human cultivation of the coconut selected, not for larger size, but for thinner husks and increased volume of endosperm, the solid “meat” or liquid “water” that provides the fruit its food value. Although these modifications for domestication would reduce the fruit’s ability to float, this ability would be irrelevant to a cultivated population.
Among modern C. nucifera, two major types or variants: a thick-husked, angular fruit and a thin-husked, spherical fruit with a higher proportion of endosperm reflect a trend of cultivation in C. nucifera: the first coconuts were of the niu kafa type, with thick husks to protect the seed, an angular, highly ridged shape to promote buoyancy during ocean dispersal, and a pointed base that allowed fruits to dig into the sand, preventing them from being washed away during germination on a new island. As early human communities began to harvest coconuts for eating and planting, they (perhaps unintentionally) selected for a larger endosperm to husk ratio and a broader, spherical base, which rendered the fruit useful as a cup or bowl, thus creating the niu vai type. The decreased buoyancy and increased fragility of this spherical, thin-husked fruit would not matter for a species that had started to be dispersed by humans and grown in plantations. Harries’ adoption of the Polynesian terms niu kafa and niu vai has now passed into general scientific discourse, and his hypothesis is generally accepted.[35][36]
Variants of C. nucifera are also categorized as Tall (var. typical) or Dwarf (var. nana).[37] The two groups are genetically distinct, with the Dwarf variety showing a greater degree of artificial selection for ornamental traits and for early germination and fruiting.[31][38] The Tall variety is outcrossing while Dwarf palms are incrossing, which has led to a much greater degree of genetic diversity within the Tall group. It is believed that the Dwarf subgroup mutated from the Tall group under human selection pressure.[39]
Dispersal[edit] Main article: Genomics of domestication It is often cited that coconuts can travel 110 days, or 3,000 miles (4,800 km), by sea and still be able to germinate.[40] This figure has been questioned based on the extremely small sample size of the paper that makes this claim.[41] Thor Heyerdahl provides an alternative, and much shorter, estimate based on his first-hand experience crossing the Pacific Ocean on the raft Kon-Tiki: “The nuts we had in baskets on deck remained edible and capable of germinating the whole way to Polynesia. But we had laid about half among the special provisions below deck, with the waves washing around them. Every single one of these was ruined by the sea water. And no coconut can float over the sea faster than a balsa raft moves with the wind behind it."[30] He also notes that several of the nuts began to germinate by the time they had been ten weeks at sea, precluding an unassisted journey of 100 days or more. However, it is more than likely that the coconut variety Heyerdahl chose for his long sea voyage was of the large, fleshy, spherical niu vai type, which Harries observed to have a significantly shorter germination type and worse buoyancy than the uncultivated niu kafa type.[31] Therefore Heyerdahl’s observations cannot be considered conclusive when it comes to determining the independent dispersal ability of the uncultivated coconut.
Drift models based on wind and ocean currents have shown that coconuts could not have drifted across the Pacific unaided.[41] This provides some circumstantial evidence that Austronesian peoples carried coconuts across the ocean and that they could not have dispersed worldwide without human agency. More recently, genomic analysis of cultivated coconut (Cocos nucifera L.) has shed light on the movements of Austronesian peoples. By examining 10 microsatelite loci, researchers found two genetically distinct subpopulations of coconut—one originating in the Indian Ocean, the other in the Pacific Ocean. However, admixture, the transfer of genetic material, evidently occurred between the two populations. Given that coconuts are ideally suited for ocean dispersal, individuals from one population possibly could have floated to the other. However, the locations of the admixture events are limited to Madagascar and coastal east Africa, and exclude the Seychelles. This pattern coincides with the known trade routes of Austronesian sailors. Additionally, a genetically distinct subpopulation of coconut on the Pacific coast of Latin America has undergone a genetic bottleneck resulting from a founder effect; however, its ancestral population is the Pacific coconut. This, together with their use of the South American sweet potato, suggests that Austronesian peoples may have sailed as far east as the Americas.[42]
Distribution[edit] The coconut has spread across much of the tropics, probably aided in many cases by seafaring people. Coconut fruit in the wild are light, buoyant and highly water resistant, and evolved to disperse significant distances via marine currents.[43] Specimens have been collected from the sea as far north as Norway.[44] In the Hawaiian Islands, the coconut is regarded as a Polynesian introduction, first brought to the islands by early Polynesian voyagers from their homelands in Oceania.[19] They have been found in the Caribbean and the Atlantic coasts of Africa and South America for less than 500 years, but evidence of their presence on the Pacific coast of South America predates Christopher Columbus's arrival in the Americas.[27] They are now almost ubiquitous between 26°N and 26°S except for the interiors of Africa and South America.
Natural habitat[edit]
Coconut germinating on Black Sand Beach, Island of Hawaii The coconut palm thrives on sandy soils and is highly tolerant of salinity. It prefers areas with abundant sunlight and regular rainfall (1500 mm to 2500 mm annually), which makes colonizing shorelines of the tropics relatively straightforward.[45] Coconuts also need high humidity (70–80%+) for optimum growth, which is why they are rarely seen in areas with low humidity, like the southeastern Mediterranean or Andalusia (Spain), even where temperatures are high enough (regularly above 24 °C or 75.2 °F). However, they can be found in humid areas with low annual precipitation such as in Karachi, Pakistan, which receives only about 250 mm (9.84 in) of rainfall per year, but is consistently warm and humid.