On 6/6/2014 4:38 PM, Jen Chendea wrote:
> In my classes, I'm learning that lactase in most humans has a natural point of diminishing, or not persisting

Jen,

  "Normal" is a very stretchable definition, including the "normal" 
weaning age.
So a lot will depend in WHAT humans you have in mind.
"Normal" humans will become absolutely or partially lactose intolerant 
by 3-5 years of age.
"Mutant" humans will keep the lactase going through their lives. Simple 
evolutionary trait - those moving North out of Africa to Europe and Asia 
had to rely on other sources of food and animal milk was a way of 
survival past the weaning age.  There were multiple additional factors 
determining the age of weaning and one of the most important was the use 
and then - the domestication of grains, which allowed "shorter" 
breastfeeding period (not as long as 5 years) and thus - increased birth 
rates, which was important for increasing population of Homo Sapiens.
Interestingly enough, there was an ancient man found frozen in Alps, who 
through the DNA analysis was diagnosed as lactose intolerant ;D

Good luck on your exams!

Alla (a mutant and a mother of a mutant, but my daughter in law is 
absolutely normal in too many ways, waaay beyond her inability to digest 
lactose ;D)

-- 
Alla Gordina, MD, IBCLC, FAAP
General Pediatrics
Breastfeeding Medicine
Adoption and Foster Care Medicine

Global Pediatrics and Family Medicine
NJ Breastfeeding Medicine Educational Initiative

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