animal host 877 host-associated 877 digestive tract 877 intestine 859 mammalian host 808 human host 519 industrialized 399 adult 254 rural 76 non-industrialized 74 child 53 urban 38 hunter-gatherer 29 elderly 27 traditional agriculturalist 23 rumen 18 infant 16 adolescent 13 agriculture 2 terrestrial 2 anthropogenic 2 built environment 2 ancient microbiome 1