Flexi Says: Lactose intolerance is probably familiar to most of you. Normally, organisms lose the ability to digest milk as they grow to adulthood. This lack of tolerance has little effect on most organisms as there really is no milk source for them as adults. However, the case with Homo sapiens is a little different. Many generations ago, some humans took to raising livestock to supplement their diet, and with this change in behavior a new resource became available, along with a benefit for anyone who could exploit it. As you may have surmised, this new resource was milk and all the products which can be made from milk. Today, about 50% of adults can tolerate the lactose found in milk and milk products. Others remain lactose intolerant.