what might be the selective advantage of not producing lactase as an adult?
What fraction of the population of Olduvai had what fraction of lactose available to them in their diet?
Assuming you have already read this thread, I do have some thoughts and suggestions, but first what answers have you considered and why?
Is there a reason why most people stop producing lactase after about childhood? Are humans not meant to consume lactose? What are some selective advantages of not producing lactase as an adult? I have thought of the question but it only led me to more questions..
The first question you should ask yourself is: Is lactose tolerance of willd type (i.e. a dominant trait) or a mutation in most of the world population?
Find the answer for this questions and your perpective on your questions will change and you should be able to formulate some answer for your question.
(Hint: look for lactose tolerance in http://www.wikipedia.org")
i think that there was a selective advantage of not producing lactase , meaning that you are not capable of digesting lactose. this will prevent competition among their children(which can digest lactase) for milk
People that are tolerant to lactose are the people that carry a mutated allelle. Lactose intolerance is the norm. So there does not seem to be any selective advantage to be intolerant to lactose since most of diet are not rich in milk and derivatives. However, it could be debated that producing lactase when no milk is present is a waste of energy. Hence, this could lead to a selective advantage.
The real selective advantage is for people that are tolerant to lactose and live in a country where the diet is rich in milk products.
The main advantage I can think of, for not producing lactase as an adult,
are in line with what iansmith mentioned. It is wasteful for our body in terms of energy and materials to continue producing enzymes when the molecule they were created for (lactase) becomes scarcer in the diet (in adults). Interesting that the cells often do have the gene to produce lactase and do so, during childhood. But upon transition to adulthood it has became disabled. In lactose tolerant people, i am thinking there may be another gene that regulates the lactase gene (tells it to turn on).
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