Nitya Jain & W Allan Walker   Nature Reviews Gastroenterology & Hepatology

Evolutionary development of the mammary gland  has driven  mammalian  survival.

Human milk has a choice of 200 – 250 unique oligosaccharides which form its third largest solid component. These oligosaccharides are partially or not digested by the infant and provide a carbon source for the intestinal flora of Bifobacterium Infantis. Genomic sequence of this strain has revealed 700 unique genes and selective pressures for evolution may be expected to continue.

German J B,   2008,  Dept. Nutrition  University of California,  Davis