Question

Describe the Old Friends Hypothesis, including hypothesized causes for gut microbiome changes.

Answer 1

• According to Old Friends Hypothesis, humans are not individual .Humans are ecossytem with microbial partners ( microbiota)  that are involved in the development and function of essentially every organ,including brain.
• Infact humans have more microbes in their gut than normal human cells and more microbial DNA and genes than human genes.
• Evolution of vertebrate occured 500 million years ago ,giving vertebrates more adaptability and flexibility because microbial gene can evolve when environment , diet or lifestyle is changed.
• Human  immune systems attacking things are not attacking because of the changes in the composition of the gut microbiota and loss of its biodiversity. This is easily proved by transferring gut microbiota from obese or depressed humans into the guts of animals, which then develop similar symptoms.
• At the same time vertebrates evolved a more complex immune system that is able to achieve the tricky task of tolerating and “farming” many hundreds of species of microbial partners (microbiota), while simultaneously protecting human from pathogens.
• These changes are occuring because of the Lifestyle changes, antibiotics, caesarean births and lack of breast-feeding which limit the transmission of maternal microbiota to the next generation. Then, unvarying diets lacking plant-derived fibre and polyphenols aggravate this loss of biodiversity.
• Human  also have less contact with the natural environment which is the source of many of the microbial partners that we need. Without these microbial inputs in early life our immune systems, endocrine systems and metabolic systems do not develop correctly, and can malfunction.