Changes

Lactose intolerance is a condition where individuals cannot digest [[lactose]], a [[sugar]] found in [[milk]].  When a lactose intolerant individual injests of milk, he or she will get a stomachache.  Other symptons include cramps and bloating.  Such individuals do not produce an [[enzyme]] called [[lactase]] that breaks down lactose after weaning.   

Lactose intolerance is a condition where individuals cannot digest [[lactose]], a [[sugar]] found in [[milk]].  When a lactose intolerant individual injests of milk, he or she will get a stomachache.  Other symptons include cramps and bloating.  Such individuals do not produce an [[enzyme]] called [[lactase]] that breaks down lactose after weaning.   

The proportion of lactose intolerant individuals varies by region on the planet.  99% of [[China|Chinese]] are lactose intolerant, whereas only 10% of [[United States|Americans]] are.  Recent research indicates that lactose intolerance is high where [[cow]]s were not domesticated.  This caused a gene to be permanently switched on, and natural selection favored a continued production of lactase during adulthood.  

The proportion of lactose intolerant individuals varies by region on the planet.  99% of [[China|Chinese]] are lactose intolerant, whereas only 10% of [[United States|Americans]] are.  Recent research indicates that lactose intolerance is high where [[cow]]s were not domesticated.  

[http://digestive.niddk.nih.gov/ddiseases/pubs/lactoseintolerance/]

[http://digestive.niddk.nih.gov/ddiseases/pubs/lactoseintolerance/]

[http://evolution.berkeley.edu/evolibrary/news/070401_lactose]

[http://evolution.berkeley.edu/evolibrary/news/070401_lactose]