Did you know that… evidence exists of our ancestors already consciously consuming fermented milk more than 5,000 years ago? That the consumption of fermentative bacteria led to changes in our DNA, such as the one that now allows us to digest the lactose in milk? That sauerkraut helped Chinese laborers build their Great Wall? That the ships sailing overseas carried lots of fermented foods that helped the passengers endure the hardships of the voyage? That the Mongols conquered their vast empire by feeding on fermented mare's milk and horse meat cured under their saddle? That the nursing mother can transmit her own character to the baby with the probiotics in the milk with which she nourishes him? Although until recently we have not been aware of its existence and its importance in our health, our intestinal flora is degenerating compared to that of our ancestors. Due to marketing needs, probiotics are removed from most fermented foods that are marketed in distribution chains. Products rich in live and active probiotics are a functional food at all levels, with multiple beneficial effects on our body, such as those they exert on the digestive, nervous, and arterial systems, on plasma lipids, or on the osteoarticular system. Lately, we have reminded about the importance of consuming foods of exotic names such as kombucha, kefir, miso, kimchi, sauerkraut because of their high level of probiotics, but the truth is we have always had at our disposal foods loaded with microorganisms, such as raw cured meats, olives, beer, wine, honey, salted fish or cheese. José Antonio Barroso, founder of one of the most prestigious food analysis laboratories in Spain, offers us a precise description of the perfect ancestral symbiosis between human beings and probiotics, that has led to be the species and civilization we are today.