I gotta preach it again: this whole "root" or "underneath" metaphor for biology has been contradicted time and time again by research on human behavior patterns, including sexuality. Sexuality is a product of a complex interplay of genetic, biological, psychological, social, and cultural factors (did I leave anything out)? There's no "root" here to discover, just the strands that make up the patterns in the behavioral fabric.
Miles
^^^^ CB: Changing the metaphor doesn't address the issue here. My question in terms of your strand metaphor would be "does a biological/genetic strand exist _at all_ for sexuality or orientation ?" You seem to answer yes.
The notion of "underneath" merely tracks the fact that genetic and biological factors are in the individual prior in the course of ontogeny to cultural factors. The complexity of the interplay with other factors doesn't mean that the expression of genetic potential are not causes of behavior
To the issue at hand, the complexity of the interplay of factors doesn't mean that _a_ cause of sexual attraction in this complexity is not genetic in many individuals.
The strands woven together metaphor doesn't contradict the notion of a biologically independent strand that exists before the other strands in the ontogeny of an individual.