Lactase Persistence

How man has cultural practices have contributed to the evolution of the sickle cell allele or persistence of lactase?

For lactase, an enzyme we all have when we are born lactase to digest milk from the mother. the enzyme used to disappear when we were done with our mother's milk. but we started to domesticate animals, which led to drink their milk. This eventually led to the enzyme does not disappear so we can digest this new milk. with people who are lactose intolerant, it is likely that the case of this enzyme has disappeared, but not always.
For sickle cell anemia, which has to do with malaria. If you have sickle cell anemia you have a resistance to malaria. would be beneficial in areas were malaria is endemic. sickle cell disease but also kill you in a relatively young age. Therefore, it would be better to be heterozygous for sickle cell, so that you receive the benefits.

Dairy products are the most compatible with blood type "B" adults. Hindus and Jews are two cultures that have the highest percentage of blood type "B" adults, and have included dairy products in their diet and traditions ...

As other poster suggested, the sickle cell allele protects one from malaria, but for those who carry this gene, it produces anemia can be fatal, so if it is not under our control, it is preferable to carry in a recessive form!