Syrian Christian \ Nasrani History
Saint Thomas Christians are an ethno-religious community of Indian Christians from the state of Kerala, who employ the East Syriac Rite and West Syriac Rite liturgical rites of Syriac Christianity. They trace their origins to the evangelistic activity of Thomas the Apostle in the 1st century. Their culture is largely derived from East Syriac, West Syriac, Hindu, Jewish, and Latin Rite influences, blended with local customs and later elements derived from indigenous Indian and European colonial contacts. Their language is Malayalam, the language of Kerala, and Syriac is used for liturgical purposes.
Genetic Analysis to deduce history of Syrian Christians based on The Formation of Human Populations in South and Central Asia paper (https://science.sciencemag.org/content/365/6457/eaat7487/tab-pdf)
Modern South Asian populations formed as a result of mixing of three distinct genetic ancestry groups (Central_Steppe_MLBA, Iranian farmer-related populations and Southern Asian hunter-gatherers (AASI))
Central_Steppe_MLBA / Steppe
This is a population that was formed in Central Asia as a result of eastward migrations of populations similiar to Corded Ware Culture, Srubnaya Culture and Potapovka culture with about ~9% mixuture with Western Siberian Hunter gatherers. The Corded Ware populations were a result of mix of 67% Yamnaya ancestry with 33% ancestry on the European cline. The migration path and formation of culture is shown below. There seems to be about two Steppe contributions to South Asian populations. The ancestry profiles are described below.
West Siberian Hunter gatherers (WSHG)
This is a group that existed in Central Eurasia that were found to be of about 30% EHG ancestry, 50% ANE ancestry, and 20% East Asian ancestry. The closest modern day populations are Sami / Khanty / Yeniseian like groups.
Steppe 1 – ( ~91% Corded ware + ~9% WSHG). Unevenly distributed ancestry in South Asia that varies from 0 – 30% and peaks in groups who claim to be of priestly status. The closest modern day populations to this non existent group are the Russian and Finnish people.
Steppe 2 – ( ~65% Corded ware + ~20% BMAC + 15% Khovsgol (Closest – Tuvanian) ). This type of admixture became more common in the Steppe populations after 900 bc and lead to formation of groups such as Scythians and Huns. Groups such as Jats and Rors, seem to have additional Steppe ancestry and claim descent from groups such as Massagetae. (https://advances.sciencemag.org/content/7/13/eabe4414).
Iranian farmer-related populations (Ganj Dareh / Belt Hotu)
This ancestry group is the largest contributor to modern South Asians and mixed in various proportions with the Southern Asian hunter-gatherers (AASI) to form Indus Valley Civilization. This ancestry group is similar in mix to Caucus Hunter Gatherers and phenotypically similar to Anatolian Early farmers. This ancestry peaks in Baloch people (~60%) and on average about ~40% among South Asians.
Southern Asian hunter-gatherers (AASI)
This is an ancestry group that existed in South Asia or in the Eastern vicinity prior to the migration of Iranian Related farmers and Steppe populations. This group is distantly related to Clade 2 populations shown below. This ancestry peaks in some populations such as Pulliyars (~70%) who were most likely similar to the first Dravidian speaking groups.
Most South Asians can be genetically described as varying degrees of admixture between (Steppe1, Iranian Related Farmer and AASI) populations except for some groups that possibly have claim descent from Steppe2 related Scythian / Huna ancestry.
Syrian Christian Population Formation
Syrian Christians were formed by mixing of two different converting populations, one set of converts that had migrated to South western India after the disintegration of Vedic culture after 500 BCE from the Western areas of the Vedic culture. This population was similar in profile to modern day North Indian Brahmins with a slight western affinity most likely reflecting the pattern of migration. On average this ancestry is about ~60%.
Another set of converting populations were similar to South Central Indian populations (Reddy, Velamas, Kammas), a population that also contributed to Nair populations. This ancestry is on average about ~40%.
Besides the above two populations, there is also a minor East Med contribution in some samples that is either a result of some of the Jews that had converted or as a result of Osroene type ancestry from Knanaya (3 – 5%).
Syrian Christian Ancestry in reference to the described populations in South Asia Paper
On average Syrian Christians have about ~20% Steppe 1 / Central Steppe MLBA + ~40% Iranian Farmer Related + ~40% AASI related ancestry. The Vedic populations with higher Steppe 1 Ancestry mixing with Lower Indus Valley populations is similar in mix to most South Asians and as a result cluster with the majority of South Asians, albeit a newer mix. The three populations that contributed to the mix are circled in small black.
South Asian populations in reference to Ancestral West Eurasian populations
South Asian populations in reference to Modern and Ancestral West Eurasian populations. Contributing populations to South Asians highlighted in red.