The Spread Of Austronesian Languages To Vietnam

Why do the people in the highlands of Vietnam speak Austronesian languages, which diffused mostly through maritime contact?

There seems to be a core of matrilineal Austronesians in Austronesian language speaking populations in Vietnam, but mostly, this appears to be a product of language shift.

This case is particularly notable in historical linguistics because so often, the origins of a language in a place are hidden deep in the depths of prehistory, while in this case, there are historical records of what was going on that genetic evidence is merely corroborating and refining. We know that Austronesian languages, which arrived only around 2500 years ago and probably suffered a great blow around 600 years ago, are the more recent linguistic layer in Vietnam than Austroasiatic languages, and can even name particular individuals and historical events that were pivotal in that process.

We also have parallel historical accounts (mostly Chinese) of the arrivals of Sino-Tibetan (i.e. Chinese, who ruled Vietnam for a thousand years starting around 111 BCE but with a Chinese kingdom in some of its territory ca. 180 BCE), Tai-Kadai (see also here noting an arrival in the 400s to 1000s CE after first mentions of their existence in Southern China ca. 500 BCE),  and Hmong-Mien languages (in the 1600s CE) in mainland Southeast Asia, in each case from what is now China.

Austronesian (AN) is the second-largest language family in the world, particularly widespread in Island Southeast Asia (ISEA) and Oceania. In Mainland Southeast Asia (MSEA), groups speaking these languages are concentrated in the highlands of Vietnam. However, our knowledge of the spread of AN-speaking populations in MSEA remains limited; in particular, it is not clear if AN languages were spread by demic or cultural diffusion. 

In this study, we present and analyze new data consisting of complete mitogenomes from 369 individuals and 847 Y-chromosomal single nucleotide polymorphisms (SNPs) from 170 individuals from all five Vietnamese Austronesian groups (VN-AN) and five neighboring Vietnamese Austroasiatic groups (VN-AA). 

We found genetic signals consistent with matrilocality in some, but not all, of the VN-AN groups. Population affinity analyses indicated connections between the AN-speaking Giarai and certain Taiwanese AN groups (Rukai, Paiwan, and Bunun). However, overall, there were closer genetic affinities between VN-AN groups and neighboring VN-AA groups, suggesting language shifts. Our study provides insights into the genetic structure of AN-speaking communities in MSEA, characterized by some contact with Taiwan and language shift in neighboring groups, indicating that the expansion of AN speakers in MSEA was a combination of cultural and demic diffusion.

Dinh Huong Thao, et al., "Investigating demic versus cultural diffusion and sex bias in the spread of Austronesian languages in Vietnam" PLOS One (June 17, 2024).

The body text of the introduction to the new article provides useful context that ties into the available linguistic and historical evidence (the link is mine):

The Austronesian language family (AN), encompassing 1256 languages spoken by approximately 360 million people, stretches from Madagascar to Hainan, Southeast Asia, Taiwan, and Near and Remote Oceania. The ancestors of Austronesian-speaking peoples are thought to have originated in the Yangtze River Delta 9–6 thousand years ago (kya) and then spread to Taiwan. Nine out of ten AN primary sub-branches are exclusive to Taiwan, while all AN languages outside of Taiwan belong to just a single primary sub-branch (Malayo-Polynesian, consisting of more than 1200 languages), strongly suggesting that Taiwan was the source of the Austronesian expansion.

AN-speaking groups in Island Southeast Asia (ISEA) have been extensively examined from cultural and biological perspectives, contributing valuable data for elucidating the history of this region. However, ethnic groups in Mainland Southeast Asia (MSEA) that speak AN languages have not yet received the same attention. In MSEA, AN-speaking groups are found in Vietnam, Thailand, and Cambodia but account for only a small proportion of the population (e.g., about 1.32% % of ~100 million people in Vietnam). 

A crucial question concerning the spread of AN-speaking groups in MSEA is the extent to which this was a process of demic diffusion (i.e., migration of AN-speaking groups from elsewhere spreading both their languages and their genes) vs. cultural diffusion (i.e., existing MSEA groups adopting an AN language with little genetic mixing with AN-speaking groups from elsewhere). 

Historical records point to the appearance of AN speakers along the coast of Indochina and the Gulf of Thailand around the 5th century BCE; the close relationship of the AN languages of Vietnam with the Malayic branch of the family points to northwest Borneo as the source of this migration. However, whether the nature of the subsequent diffusion of AN languages was demic or cultural continues to be an open question. 

Here, we address this question, and potential sex bias in the spread of AN ancestry, by analyzing mtDNA and Y chromosome variation in AN-speaking groups from Vietnam.

Vietnam (VN), with its long coastline, occupies a key geographical position in MSEA and is home to 54 ethnic groups speaking languages classified into five language families: Austroasiastic (AA), Tai-Kadai (TK; also known as Kra-Dai), Hmong-Mien (HM), Sino Tibetan (ST) and Austronesian (AN). There are five recognized AN-speaking groups in Vietnam: Cham, Churu, Ede, Giarai, and Raglay, together accounting for ~1.32% of the national census size. It is thought that the first AN-speaking group to arrive in Vietnam were the ancestors of the Cham on the South Central Coast in 500 BCE, who probably originated in Borneo. From there, the Cham rapidly extended their territory and established the Champa kingdom. In the process, their languages underwent profound contact-induced changes due to the language shift of the autochthonous populations who were politically subordinate to the Cham. Modern Austronesian-speaking communities in Vietnam (VN-AN) mainly occupy the mountainous Central Highlands and the South Central coastline. Their social customs, traditions, and family dynamics are related to the ancient Champa and comparable to their counterparts in ISEA. To date, the maternal genetic ancestry of the Vietnamese Cham was described based only on the mtDNA HVS region, which provides limited resolution, while complete mtDNA genome sequences are available for two groups of Cham from Cambodia. Recent studies examined both uniparental markers and genome-wide data for two AN-speaking groups, Ede and Giarai. These findings were compared with other neighboring populations from different language families but not with other AN-speaking ethnicities on the mainland due to data scarcity, hindering attempts to trace the dispersal of the AN languages in MSEA.

The Wikipedia link explains that:

The Chams descended from seafaring settlers who reached the Southeast Asian mainland from Borneo about the time of the Sa Huỳnh culture between 1000 BCE and 200 CE, the predecessor of the Cham kingdom. The Cham language is part of the Austronesian family. According to one study, Cham is related most closely to modern Acehnese in northern Sumatra.

The Sa Huỳnh culture was an Austronesian seafaring culture that centered around present-day Central Vietnam coastal region. During its heyday, the culture distributed across the Central Vietnam coast and had commercial links across the South China Sea with the Philippine archipelago and even with Taiwan (through Maritime Jade Road, Sa Huynh-Kalanay Interaction Sphere), which now most archaeologists and scholars have consentient [sic] determined and are no longer hesitant in linking with the ancestors of the Austronesian Cham and Chamic-speaking peoples.

The Champa Kingdom mostly died in 1471 CE, although it limped along as a semi-autonomous region for almost four more centuries:

In the Cham–Vietnamese War (1471), Champa suffered serious defeats at the hands of the Vietnamese, in which 120,000 people were either captured or killed. 50 members of the Cham royal family and some 20–30,000 were taken prisoners and deported, including the king of Champa Tra Toan, who died along his way to the north in captivity. Contemporary reports from China record a Cham envoy telling to the Chinese court: "Annam destroyed our country" with additional notes of massive burning and looting, in which 40 to 60,000 people were slaughtered. The kingdom was reduced to a small enclave near Nha Trang and Phan Rang with many Chams fleeing to Cambodia.

Champa was reduced to the principalities of Panduranga and Kauthara at the beginning of the 16th century. Kauthara was annexed by the Vietnamese in 1653. From 1799 to 1832, Panduranga lost its hereditary monarchy status, with kings selected and appointed by the Vietnamese court in Huế.

The last remaining principality of Champa, Panduranga, survived until August 1832, when Minh Mang of Vietnam began his purge against rival Le Van Duyet's faction, and accused the Cham leaders of supporting Duyet. Minh Mang ordered the last Cham king Po Phaok The and the vice-king Po Dhar Kaok to be arrested in Hue, while incorporating the last remnants of Champa into what are the Ninh Thuan and Binh Thuan provinces.

To enforce his finger grip, Minh Mang appointed Vietnamese bureaucrats from Hue to govern the Cham directly in phủ Ninh Thuan while removing the traditional Cham customary laws. Administratively, Panduranga was integrated into Vietnam proper with harsh measures. These reforms were known as cải thổ quy lưu ("replacing thổ [aboriginal] chieftains by circulating bureaucratic system"). Speaking Vietnamese and following Vietnamese customs became strictly mandatory for the Cham subjects. Cham culture and Cham identity were rapidly, systematically destroyed. Vietnamese settlers seized most of Cham farmlands and commodity productions, pushing the Cham to far-inland arid highlands, and the Cham were subjected to heavy taxations and mandated conscriptions. Two widespread Cham revolts against Minh Mang's oppression arose in 1833–1835, the latter led by khatib Ja Thak Wa - a Cham Bani cleric – which was more successful and even briefly reestablished a Cham state for a short period of time, before being crushed by Minh Mang's forces.

The unfortunate defeat of the people of Panduranga in their struggle against Vietnamese oppression also sealed their and remnant of Champa's fate. A large chunk of the Cham in Panduranga were subjected to forced assimilation by the Vietnamese, while many Cham, including indigenous highland peoples, were indiscriminately killed by the Vietnamese in massacres, particularly from 1832 to 1836, during the Sumat and Ja Thak Wa uprisings. Bani mosques were razed the ground. Temples were set on fire. Cham villages and their aquatic livelihoods were annihilated. By that time, the Cham totally lost their ancestors' seafaring and shipbuilding traditions.