While I believe the research points to the potential influence of environmental factors broadly speaking, I think the Lifesite article overstates some of the findings.
Mrs. Nicolosi correctly notes the population size – 2,000,355 native-born Danes between the ages of 18 and 49 but does not clarify that the research did not examine childhood correlates for the unmarried Danes. For gays that would mean that the study examined social factors for the married gays or about 1-5% of the gay population in Denmark (n=1890 men; n=1573 women). The study is still quite large but conclusions cannot be generalized with certainty to unpartnered gay people.
In reading the Lifesite article, one could get the impression that gays and straight were directly compared and interrelated. In other words, if homosexual rates of marriage go up then heterosexual rates go down. Not necessarily so. The childhood correlates were independently compared to gay and straight marriage decisions. People with unknown fathers were indeed less likely to marry heterosexually (“Men and women with “unknown fathers” were significantly less likely to marry a person of the opposite sex than were their peers with known fathers”) but there was no significant relationship between unknown fathers and elevated homosexual marriage. Reduced heterosexual marriage rates do not necessarily mean increased same-sex marriage. I do not think Mrs. Nicolosi’s article is clear on this point.
Another point that is misleading from the Lifesite article is this bullet point: “Men whose parents divorced before their 6th birthday were 39% more likely to marry homosexually than peers from intact parental marriages.” While this is a true finding, Mrs. Nicolosi does not report that there were only 35 men in this category and that the difference in marriage rates between this group and the comparison group was not statistically significant. Thus, although true, one cannot attach much importance to it.
It is also relevant to point out that nearly 83% of the gay men in the study did not experience parental divorce prior to their 18th birthday. Thus, the vast majority of these men enjoyed intact families through their childhood.
As I read the study, there are several provocative findings, including:
1. The fraternal birth order effect did not show up, 2. Cohabitation is correlated with higher probability of marrying homosexually, 3. Divorce has negative impacts on marriage rates for staights, and 4. Elevated rates of homosexual marriage are associated with being born in a metropolitan area versus lowered rates if you live in a rural area.