what type of social groups or hierarchy do these people adhere to?
Thry were divided into three strata: the "Andriana" (nobles), the "Hova" (freemen), and the lowest strata called "Andevo" (slaves)
Merina people
The Merine people were divided into three strata: the "Andriana" (nobles), the "Hova" (freemen), and the lowest strata called "Andevo" (slaves).

what is ambohimanga? A hill and traditional fortified royal settlement in Madagascar from where did it get its name? It is a noun-adjective compound in the standard Malagasy language composed of two parts: "ambohi", meaning "hill", and "manga", which can mean "sacred", "blue", "beautiful" or "good" which people reside in that settlement? Merina people mention a few rituals followed by them? They ritually kill their cattle with unusual violence, cook and consume beef prepared thereafter ceremoniously
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Merina people [SEP] Social stratification
Each strata had been then hierarchically subdivided. The "Andriana" are divided into six sub-strata, each had an inherited occupation, and were endogamous. The nineteenth century records show that "Andevo" or slaves were imported blacks, and they constituted about a third of the Merina society. The Merina society sold highland slaves to both Muslim and European slave traders on Madagascar coast, as well as bought East African and southeast African slaves from them for their own plantations between 1795 and 1895. Marriage and any sexual relations between the "fotsy" and "mainty" were a taboo. According to a 2012 report by Gulnara Shahinian – the United Nation's Special Rapporteur on contemporary forms of slavery, the descendants of former slave castes continue to suffer in contemporary Madagascar Merina society, and inter-caste marriages socially ostracized.