In response to many e-mails to listservers and/or to me personally,
some clarifications, via a very general sketch of "three layers" of neural
and immunological function:
Background: My recent postings sketched/suggested an immunological basis to
sexual- and gender-orientations and that the causal substrates may exist
at the level of "innate immunity", even transcending (ie evolutionarily
preceeding) major histocompatibility complex antigen-presentation genes and
immunoglobulin genes.
THREE LAYERS:
Layer Three: The primate visual and auditory systems and their links with
amygdaloid, hippocampal, and other brain structures are certainly part of
how we process sexually significant non-chemo-signal stimuli as well as
pheromonal molecules of the olfactory and vomeronasal sort.
Layer Two: MHC effects have been shown in human odor/scent evaluation and
also have been documented in mating-choice preferences. Vomeronasal and
olfactory receptors and their neural routes are within this evolutionary
"layer".
Comment: Item #1 seems to function regardless of sexual orientation;
and item #2 is studied primarily in relation to heterosexual
orientation, regardless of species.
Layer One in yeast: In contrast, the yeast Saccharomyces cerevisiae (ySc)
has a mating system with several clear sexually dimorphisms:
a. The alpha-factor yeast produces alpha-factor pheromones and has on its
cell surface an a-factor receptor and responds to a-factor pheromone.
b. The a-factor yeast produces a-factor pheromones and has cell-surface
receptors for and responds to alpha-factor pheromones.
Layer One in humans and other mammals: ySc has neither olfactory nor
vomeronasal nor nasal-trigeminal receptors or neural systems; and what
seems to be an unresearched possibility is that certain kinds of
sexually significant chemo-signaling in vertebrates occurs in tissues
other than olfactory and vomeronasal. Three possibilities are (i)
epidermis, (ii) respiratory epithelium, and (iii) lymphoid tissue
anywhere within the nasal cavity.
In my hypothesis of sexual and gender orientations, their primary
substrate is within Layer One, thereby transcending (being more basic
than) (i) visuals and conditionings, (ii) MHC-related filterings we
observe as mating-type choices among heterosexual organisms regardless of
species, and (iii) olfactory and vomeronasal processing of sexually
significant odors and pheromones of the mammalian sort.
***
EVOLUTIONARY QUESTIONS:
