The first study your link sites.
http://www.ncbi.nlm.nih.gov/pubmed/11206089
Homosexuals are 2-3% of population. The fact that the study found a 30-60% chance that a person is homosexual if his or her twin is homosexual, is the dictionary definition of genetic inheritance (if study is accurate).
But we already knew this from the Bible. Sinner are born (Christian view) not made by society (Marxist view). I spoke my mind, thanks for the link, wish I had access to full paper :(
There’s 2 links. The first one is the link to the complete book.