This study examines the gut microbiome across different populations, ages, and geographical regions to understand how these factors influence microbial composition and function. The researchers analyzed fecal samples from 531 individuals, including healthy Amerindians from Venezuela, rural Malawians, and metropolitan USA residents, covering infants, children, teenagers, and adults. They found that the gut microbiome undergoes functional maturation during the first three years of life, with age-associated changes in genes involved in vitamin biosynthesis and metabolism. Pronounced differences were observed between the USA and other populations, particularly in early infancy and adulthood. The study also highlighted the importance of family resemblance in the gut microbiome, suggesting that cultural and environmental factors play a significant role in shaping microbial communities. The findings underscore the need to consider the microbiome in evaluating human development, nutritional needs, and physiological variations, especially in the context of Westernization.This study examines the gut microbiome across different populations, ages, and geographical regions to understand how these factors influence microbial composition and function. The researchers analyzed fecal samples from 531 individuals, including healthy Amerindians from Venezuela, rural Malawians, and metropolitan USA residents, covering infants, children, teenagers, and adults. They found that the gut microbiome undergoes functional maturation during the first three years of life, with age-associated changes in genes involved in vitamin biosynthesis and metabolism. Pronounced differences were observed between the USA and other populations, particularly in early infancy and adulthood. The study also highlighted the importance of family resemblance in the gut microbiome, suggesting that cultural and environmental factors play a significant role in shaping microbial communities. The findings underscore the need to consider the microbiome in evaluating human development, nutritional needs, and physiological variations, especially in the context of Westernization.