Found a very interesting para in the Review section of UK Sunday Telegraph,
22nd March  It is all about Genes.  Article written by Robert Matthews.  It
says

 ' Marc Feldman, at Stanford California, is one of a growing number of
theoretical biologists now using "gene-culture" theory to study evolutionary
conundrums beyond the reach of gene-centred Darwinism.  For example, one long-
standing puzzle concerns the fact that most humans are genetically incapable
of digesting milk.  Yet, in countries such as England, with long histories of
dairy farming, studies show that 90% of the people possess the necessary genes
- over four times the level in non-dairy regions.  Feldman and his colleagues
have shown that this powerful clustering effect cannot be explained solely by
Darwinian selection of "favourable" genes.  It requires the extra influence of
cultural pressure, with children in dairy regions being more likely to
"inherit" the use of milk as a key source of nutrition from their parents.  By
taking into account both forms of inheritance, Feldman and his colleagues have
been able to explain, with mathematical precision, the details of milk
intolerance among humans.

The Telegraph has an URL    http://www.telegraph.co.uk        I have not
visited it.

Helen M. Woodman, National Childbirth Trust Breastfeeding Counsellor UK