Complex sentence: Granted, the FWI Indians had to renounce most of their cultural, linguistic and religious indianness under the pressures of French and Christian acculturation that was already the condition of the Blacks when the first indentured workers arrived.
Split into simpler sentences: Granted, the FWI Indians had to renounce a good amount of their cultural, linguistic and religious indianness, under the pressures of French and Christian acculturation. That was already the condition of the Blacks when the first indentured workers arrived.