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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Island | 3/5 | https://en.wikipedia.org/wiki/Island | reference | science, encyclopedia | 2026-05-05T07:35:12.739706+00:00 | kb-cron |
Species endemic to islands show a common evolutionary trajectory. Foster's rule (also known as the island rule), states that small mammals such as rodents evolve to become larger, known as island gigantism. One such example is the giant tortoise of the Seychelles, though it is unknown if it grew in size before or after reaching the island. Larger animals such as the hippopotamus tend to become smaller, such as in the case of the pygmy hippopotamus. This is known as insular dwarfism. In the case of smaller animals, it has been hypothesized that animals on islands may have fewer predators and competitors, resulting in selection pressure towards larger animals. Larger animals may exhaust food resources quickly due to their size, causing malnutrition in their young, resulting in a selection pressure for smaller animals that require less food. Having fewer predators would mean these animals did not need not be large to survive.
=== Darwin, the Galápagos, and natural selection === Charles Darwin formulated the theory of natural selection through the study of island ecology. The species he observed on the Galápagos Islands, including tanager birds, contributed to his understanding of how evolution works. He first traveled to the islands as a naturalist on HMS Beagle in 1835, as part of a five-year circumnavigation of Earth. He wrote that "the different islands to a considerable extent are inhabited by a different set of beings". Through the study of the finches and other animals he realized that organisms survive by changing to adapt to their habitat. It would be over twenty years before he published his theories in On the Origin of Species.
== Humans and islands ==
=== History of exploration ===
The first evidence of humans colonizing islands probably occurred in the Paleolithic era, 100,000 to 200,000 years ago. Reaching the Indonesian islands of Flores and Timor would have required crossing distances of water of at least 29 km (18 mi). Some islands, such as Honshu, were probably connected to the mainland with a land bridge that allowed humans to colonize it before it became an island. The first people to colonize distant oceanic islands were the Polynesians. Many of the previous island settlements required traveling distances of less than 100 km (62 mi), whereas Polynesians may have traveled 2,000–3,200 km (1,200–2,000 mi) to settle islands such as Tahiti. They would send navigators to sail the ocean without the aid of navigational instruments to discover new islands for settlement. Between 1100 and 800 BC, Polynesians sailed East from New Guinea and the Solomon Islands and reached the islands that make up the modern-day Fiji and Samoa. The furthest extent of this migration would be Easter Island in the East, and New Zealand in the South, with New Zealand's first settlements between 1250 and 1300. Historians have sought to understand why some remote islands have always been uninhabited, while others, especially in the Pacific Ocean, have long been populated by humans. Generally, larger islands are more likely to be able to sustain humans and thus are more likely to have been settled. Small islands that cannot sustain populations on their own can still be habitable if they are within a "commuting" distance to an island that has enough resources to be sustainable. The presence of an island is marked by seabirds, differences in cloud and weather patterns, as well as changes in the direction of waves. It is also possible for human populations to have gone extinct on islands, evidenced by explorers finding islands that show evidence of habitation but no life. Not all islands were or are inhabited by maritime cultures. In the past, some societies were found to have lost their seafaring ability over time, such as the case of the Canary Islands, which were occupied by an indigenous people since the island's first discovery in the first century until being conquered by the Spanish Empire in 1496. It has been hypothesized that since the inhabitants had little incentive for trade and had little to any contact with the mainland, they had no need for boats. The motivation for island exploration has been the subject of research and debate. Some early historians previously argued that early island colonization was unintentional, perhaps by a raft being swept out to sea. Others compare the motivations of Polynesian and similar explorers with those of Christopher Columbus, the explorer who sailed westward over the Atlantic Ocean in search of an alternate route to the East Indies. These historians theorize that successful explorers were rewarded with recognition and wealth, leading others to attempt possibly dangerous expeditions to discover more islands, usually with poor results.
=== Lifestyle === About 10% of the world's population lives on islands. The study of the culture of islands is known as island studies. The interest in the study of islands is due to their unique cultures and natural environments that differ from mainland cultures. This is for a few reasons: First, the obvious political and geographic isolation from mainland cultures. Second, unique restraints on resources and ecology creating marine-focused cultures with a focus on fishing and sailing. Third, a lasting historical and political significance of islands.