Final answer:
Gut flora is established through contact with the mother's bacteria during birth and the introduction of beneficial bacteria from breast milk or formula. It continues to evolve and become more diverse throughout a person's life.
Step-by-step explanation:
The establishment of gut flora, or the microbial community in the gut, occurs through several processes. The first colonization of gut flora in newborns happens through contact with the mother's vaginal, fecal, and skin bacteria during natural birth. Breast milk or formula also introduces beneficial bacteria into the infant's gut. The gut flora continues to evolve and become more diverse throughout a person's life, influenced by factors such as diet, lifestyle, and health.