Consanguinity and reproductive behaviour in a tribal population 'the Baiga' in Madhya Pradesh, India.

We have studied the marriage pattern and reproductive behaviour in a single Central Indian primitive tribe, the Baiga. Parents were consanguineous in 34% of marriages (19.2% mother's brother's daughter (MBD), 13.1% father's sister's daughter (FSD) and 1.7% were double first cross-cousins (DFCC). Fertility levels were significantly higher (p < 0.05) in related couples (4.7 offspring/couple) than unrelated couples (4.2/couple). Mortality (up to 20 years) was 19%. In the offspring of consanguineous couples it was higher (19.7%) than in the offspring of unrelated couples (18.6%) but the difference was not statistically significant. In consanguineous couples the reproductive period was longer than in unrelated couples, probably to allow compensation for increased reproductive losses (infant and childhood deaths). The level of social as compared to genetic parenting was about 35% as measured by tracking the inheritance of sickle gene, and allowance must be made for this in assessing the influence of consanguineous marriage on fertility and mortality.