It makes sense that boys might require a higher fat, protein and calorie content in milk than girls. We already know that boys generally take a greater volume of milk. That's a cost to the mother as well. The evolutionary explanation that sons can have more babies and are more worth the investment is speculation. Remember the scientist who postulated that menstruation existed to regularly wash out the dirty male secretions from the vagina? That was based on a non-breastfeeding menstrual pattern, not the biological norm for most of human history. It can be so hard for us human beings to seperate out our culture from our science. Alternatively, sons provide assistance to the family, and in many cultures stay with the birth family and import their wives. In my n of 1 (family), my 24 y o son is very happy to carry heavy bags, get items down from up high, and kill insects that have wandered into the family abode. He'll also cook and shop, so maybe he's just a helpful sort (good advertisement for bf and attachment parenting). His sister is similarly wonderful, but much less enthusiastic about strength and reach requiring tasks. Catherine Watson Genna, BS, IBCLC NYC cwgenna.com *********************************************** Archives: http://community.lsoft.com/archives/LACTNET.html To reach list owners: [log in to unmask] Mail all list management commands to: [log in to unmask] COMMANDS: 1. To temporarily stop your subscription write in the body of an email: set lactnet nomail 2. To start it again: set lactnet mail 3. To unsubscribe: unsubscribe lactnet 4. To get a comprehensive list of rules and directions: get lactnet welcome