How do I love Thee…

I’m not a romantic. T’is why I am late in my timing, one week post Valentine’s Day, to discuss the biological basis of love and mate-choice. You see how I say that, “the biological basis of love and mate choice”? Why is it that I must suggest that people don’t just find their true love with a gaze across a crowded room, but instead are driven by some pre-determined genetic factor that ties in with that whole survival-of-the-fittest story? …Because I am not a romantic? Maybe. But more likely because I am, after all, a biologist, and it is rare that I won’t try to find a biological or evolutionary explanation for most every social and cultural issue I contemplate. For the non-human animal world, the idea of genetic and evolutionary factors driving mate-choice is well established. I myself have known this since the ’70s, thanks to episodes of Wild Kingdom, which not only taught me that if you don’t have the genes that make you run fast, you’re gonna be someone’s dinner; but also, that if you DO have the genes that give you the biggest rack, the best dance, and the nicest tail (feathers) then you were gonna get taken out to dinner. I guess for humans we can also say that big racks play a role in mate choice along with other outward physical attributes, social status, and income earning potential (did I say I wasn‘t a romantic…ha!) . But what other animal instincts are still left with us that help us choose our mate? As humans we don’t really think about the olfactory cues that we unknowingly might send to our counterparts of the opposite sex; but through scientific studies this has been positively demonstrated by various studies including the “sweaty T-shirt experiments” (reviewed in (1)). Along with those experiments, numerous studies have shown that, like animals, humans have signature odors (reviewed in (2)), and those signature odors are related to the genotype of one’s MHC (major histocompatibility complex). The “sweaty T-shirt experiments” showed this at work in humans and revealed that females prefer the odor of T-shirts worn by males of a dissimilar genotype for the MHC. Additionally, there are other studies that reported spouses of a particular population were significantly MHC-dissimilar over random pairs of individuals (1). So why would one care about someone’s MHC? The MHC is a group of genes that encode proteins that play a role in self-recognition and are critical to immunity. They are glycoproteins expressed on the surface of nearly every cell type and function to display antigens that define a cell as “self”. Recognition of “self” is key to the innate properties of the immune system. By recognizing “self”, the immune system is kept from launching an immune response against one’s self; but in the event of infection, foreign peptides incorporated and displayed by MHC proteins can illicit an effective immune response. So, it is theorized that if a population of individuals exhibits a variety of MHC polymorphism, that might ensure that a population would be safeguarded against an epidemic infection (reviewed in (2)). What this means is that if your baby’s daddy (or momma) provides variety of MHC to your offspring, then there is a survival advantage! Now comes my attempt at being match-maker: How does one choose the best MHC? Firstly, listen to your nose, because it seems that these self-antigen presenting MHC proteins can be shed from cells, into the bloodstream, and to body fluids such as sweat, urine, or saliva (so that’s what kissing is all about!), making them available as odorants and attractants for olfactory analysis; secondly, choose an MHC-type different from your own so that your offspring receives alternate alleles that brings an advantageous variety to their immune system. Lastly, just when you decide, “He/She is not my type”, think again, because that just might be the cue you need to go for it. Fly to her side and make her your own or all thru your life you may dream all alone, and once you have found her, never let her go!


References

1. R. Chaix, C. Cao, P. Donnelly, PLoS. Genet. 4, e1000184 (2008).

2. P. B. Singh, Reproduction. 121, 529 (2001).

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