A couple of intriguing papers to add to this collection:
ISLAND SYSTEMS
The analysis of Near Time or Late Quaternary Extinctions (LQE; the terms may be used interchangeably) has become a significant field in recent anthropology. Little widespread consensus has been reached (see for instance MacPhee 1999, Martin and Klein 1984), but one fact that is generally agreed upon is that extinction patterns tend to follow the spread of human populations (Martin and Steadman 1999, but see Anderson 2002). Specifically for present purposes, islands more than 62 miles (100 km) from the mainland tend not to show significant extinctions before 18,000 BC and islands in general tend to lag significantly behind continental extinctions in the same region. If we assume that LQE is primarily an anthropogenic phenomenon (as indeed Martin and Steadman conclude) then this pattern becomes easily explainable as a factor of the ocean as an obstacle to human expansion. Thus in the first case islands present a good model for faunal extinctions because they tend to be inhabited only late in the archaeological record (allowing easier tracking of human environmental impact) and only by relatively technologically advanced peoples.
Another convenience of island study is isolation. By nature island ecosystems are isolated, and as Kirch (1997) has noted isolation can be a more significant factor in environmental damage than population size. Even among islands, those that are more isolated tend to be more susceptible to damage than those that are smaller but more easily accessible to replacement species. Isolation functions to demonstrate the dramatic nature of some extinctions; for instance in Polynesia as much as 2/3 of all bird species were lost (Steadman 1995). Given the relative infrequency of species arrival in isolated island systems, it also tends to ensure that the damaged environment has great difficulty repairing itself, highlighting the extent of the damage.
Island systems also tend to be restricted in species diversity based on the difficulty of access (Paulay 1994). Mammals that manage to reach island systems tend to be smaller than their continental relatives, and in extremely isolated islands like those of the Polynesian triangle (defined with end points at New Zealand, Hawai’i, and Easter Island [Bellwood 1978, Kirch 2000]) the entirety of the mammalian population consists of bats. The lack of “keystone” species (that is, those that hold essential niches in the ecological structure of the given ecosystem) such as grazing mammals necessitates the radiation of unusual or even bizarre species forms to fill the gap. Some of the most striking examples of this phenomenon (for instance the relatively famous moas) will be presented in the discussion of New Zealand. Perhaps the most important aspect of this species barrier, particularly on oceanic islands (i.e. those never connected to continents), is the lack of natural predators. As Paulay (ibid.) details, island species tend to be poorly suited to withstand the arrival of new predators. Islands tend to host “relic taxa” which have long since gone extinct on continents. Island ecosystems also promote the secondary development of helplessness on the part of newly arriving species that no longer need to divert bodily resources to escape or defense.
All the reasons listed above apply with even more force to the Polynesian triangle. Polynesia was settled extremely late according to the archaeological record, beginning around 1500 BC (Bellwood 1978, 1997, Kirch 2000) by a population of advanced horticulturalists. The entirety of Polynesia is highly isolated and thus the arrival of human populations severely damaged native ecosystems on every single island. This damage has yet to be repaired (Steadman 1989, 1995, 1997). Perhaps most importantly to the sudden and severe nature of Polynesian extinctions native species on Polynesian islands was the fabled tameness of native birds. It was said that if a man were to walk up to a bird and push it over the bird wouldn’t even react until it fell to the ground.
In sum, the Polynesian islands present a unique situation, a kind of “natural laboratory” in which a large scale and widespread multispecies extinctions traceable to one culture and one short period of time can be easily observed from the archaeological record.
Settlement Patterns in South Pacific Island Communities
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Since Thor Heyerdahl asserted that Polynesia was first colonized from the Americas (Heyerdahl 1950), geneticists have sought—but have not found—any evidence to support his theories. Here, Native American Y chromosomes are detected on the Polynesian island of Rapa. However, this, together with other odd features of the island’s Y-chromosomal gene pool, is best explained as the genetic impact of a 19th century Peruvian slave trade in Polynesia. These findings underscore the need to account for history before turning to prehistory and the value of archival research to understanding modern genetic diversity. Although the impact of the Atlantic slave trade on the distribution of modern genetic diversity has been well appreciated, this represents the first study investigating the impact of this underappreciated episode on genetic diversity in the Pacific.
Native American Y Chromosomes in Polynesia: The Genetic Impact of the Polynesian Slave Trade
