To all -
New here: easy does it...
Spent quite a bit of time studying this and other genetic curiosities, like the debate over whether there is a "GAY" gene (you know if they ever bring back eugenics some will be looking to abort GAY fetuses). Certainly will be an interesting debate and might make quite a dilemma for the right-wing, anti-gay, gay=sin religious folks vis a vis their abortion stance. Wooh!
The research so far has only yielded one broad statistical truth that passes the necessary tests of correlation: the more male children a woman has, there is a statistically significant increase in the % turning out to be gay. This gives credence to the much more complicated model that it is not a single gene, nor necessarily a combination of genes, but that hormones in gestation (1st trimester) play a large role. In evolutionary terms, it makes sense that if too many males are being born, nature might try to compensate for the increased competition for mates with which to procreate. Just an interesting theory at this point.
As far as penis size goes, they have established a link between the "growth hormone" receptors in the penile tissues (GH, IF-1, IGF-1, and a host of others) together with the amount of male androgens produced and bio-available in the body of the mother early in the pregnancy. Theoretically, an "ideal" combination of genes from the father favoring larger size, also resulting in an excess of penile growth receptors, an excess of bio-available testosterone androgens in the mother as well as possible hormonal factors affected by repeated or the first pregnancy with male offspring would have to create a "perfect storm" of factors to develop an extraordinarily large penis (more than 3 standard deviations above the mean values for length & girth).
Genetics definitely plays some role, but the proteins they generate have a multitude of functions, including a "turn off" role that accounts for the ending of further development in many areas.
As a gay man, I have fantasies (like most of us) and one I like to play with IN MY HEAD assumes a scenario where these complex interactions and genetic, hormonal & other factors had all been sorted out for penis length and girth, as well as testicle size (by the way, check out "fragile-X syndrome" as well as macroorchidism & macrophallus to see what side effects bio-engineering might have on the rest of the human life). I like to fantasize about "breeding" for male offspring afflicted with a syndrome where the penis and testicle develop early (see: precocious puberty) and continue to enlarge without ever fully developing the other puberty attributes (except perhaps the fusing of the growth plates at a height of 6' 7").
I then imagine the middle & high school gym classes of these boys where their flaccid size of 7-9" arouses the attentions of male friends, coaches, teachers, the school nurse etc. I imagine the pediatric visits, ultimately yielding the need for design of a spandex "truss" to support the weight of the testicles, each of which could approach 1/2 pound, and the choice of underwear and clothing to help conceal the condition and reduce discomfort from the sheer weight of all that "junk." I picture the size factor as slowing down around the age of 22, with a length of 14-15", a plum-size glans and girth at the "base" (when erect) of 9-10" around. The fun stuff is imagining the normal experiences of life (family trips to the beach, camping, hiking, etc) as well as athletics, and visits to extended family where younger male cousins have to share their space with someone like that, and the "shock and awe" that would accompany observing a member larger than any seen before.
Well, it's a nice JO fantasy, but in real life I deal with what nature gave me.