Why are "Chagossians" considered indigenous to Chagos Islands despite having spent less than 200 years there?

Question

According to Wikipedia, the ancestors of the Chagossians first arrived on the islands in 1793 as slaves for French coconut plantations. Their descendants were expelled in 1965, meaning their total presence on the islands lasted at most 172 years. Throughout this period, the islands were under French or British control, leaving the Chagossians with 0 years of sovereign rule over the territory.

This brief tenure makes the Chagossians' claim to indigeneity uniquely short compared to other recognized indigenous peoples worldwide. Only two other groups have inhabited their territories for less than a millennium, and both arrived as independent settlers rather than as slaves:

• Inuit (Greenland): Migrated from Alaska around 1200 CE, at a time when Norse settlers had already staked a claim. After Norse colonies vanished in the early 15th century, the Inuit had about 300 years of de facto independence before Denmark reasserted control in 1721. Their claim is likewise contentious, as Europeans (led by Erik the Red around 982 CE) had settled Greenland roughly two centuries before the Inuit arrival, making it a unique example of reverse colonization.

• Maori (New Zealand): Arrived circa 1300 CE and maintained independence until British colonization in 1840. Total period of sovereignty: 540 years; overall presence: 700 years.

All other recognized indigenous cultures have inhabited their lands for at least a millennium, so their claims are clear and hard to dispute. This raises the question: Why are Chagossians classified as "indigenous"? They never exercised independent control over the islands, were initially transported there by European powers, and resided there for at most 172 years—a duration far shorter than every other culture on Earth, save perhaps the Inuit.

Answer 1

Frame shift

If we forget the specific use of the term "indigenous" for a second and we stick to your concerns about the validity of those claims, you'd find that about the same objections can be applied to the Falkland islanders' claims.

Yet, the UK makes a great big deal about the Falklanders' wishes not to be part of Argentina.

This same logic can be applied to most of the Caribbean islands, where the historical non-white population is almost entirely people imported from Africa. i.e. in much the same boat as the Chagossians.

i.e. Should the ex-colonial power be allowed to do as it pleases and chuck people out from places they have lived for generations?

To me that's the core of the question wrt Chagossians' claims. The word "indigenous" does seem a bit misused here, at least in the layman's meaning of the word. Maybe there is a particular UN or human rights aspect that motivates its use and maybe someone else can answer on that basis.

p.s. In the case of the Caribbean, indigenous does refer to the original inhabitants, not the African-descended residents.

Answer 2

The report you linked to defends their indigenous status from multiple standpoints, but the one you seem to care about is as I suspected:

Crucially, no other group can claim a prior historical or ancestral relationship to Chagos and trump the Ilois as Chagos’s first inhabitants.

The report even goes in some detail how that meshes with various (operationalized) definitions of indigenous:

As the first permanent inhabitants of Chagos and with no other group able to claim or claiming prior habitation, the Ilois meet Daes’s factor of “Priority in time, with respect to the occupation and use of a specific territory” (1996:22). The Ilois also meet Daes’s factor of having “an experience of subjugation, marginalization, dispossession, exclusion or discrimination, whether or not these conditions persist” (1996:22), in both their expulsion from Chagos and their subsequent lives in Mauritius and Seychelles (as described in 3.5.). For Kingsbury’s framework, although the Ilois did not live in Chagos for thousands of years, they had nearly 200 years of continual residence over five or more generations of ancestry. In this way the Ilois also meet Kingsbury’s “essential requirement” of “long connection with the region” (1998:455). The Ilois likewise meet Cobo’s underlying emphasis on “historical continuity” in having occupied the lands of their ancestors going back to the late 18th century and in having “common ancestry with the original occupants of these lands.” They meet ILO No. 169’s emphasis on “descent from the populations” originally in a territory. The Ilois actually reach the requirements of ILO No. 169 in a very literal sense under a strict reading of the convention: Given that the current state boundaries of Chagos were created in 1965 with the establishment of the BIOT, the Ilois are the descendants of the “populations which inhabited the country, or a geographical region to which the country belongs, at the time of conquest or colonization or the establishment of present state boundaries” (International Labour Organisation 1991:Art. 1; emphasis added). Though the Ilois do not have the same depth of historical connection with a region or territory as Aboriginal Australians or the original peoples of the Americas, historical evidence shows that before their expulsion, the Ilois had a strong, ongoing, and lengthy ancestral connection with the Chagos Archipelago and its original inhabitants. With no other group of people able to claim prior habitation or historical connection with the islands, the evidence strongly suggests that the Ilois meet the general requirement of having a historical and temporal connection with Chagos and its ancestral inhabitants.