Form and Function

Canadian Public Radio to the rescue again with a show on how humans use smell to pick their mates. The research started out with a group of men each wearing the same shirt overnight for two nights and then having women smell the shirts in a lab and report how appealing they found the smell of each shirt. (Hopefully the women were receiving some sort of stipend for their part in this.) The results indicated that women prefer the smell of men who are genetically dissimilar to themselves in the area of MHC genes. (Whether this "MHC" is the same as the "MHC" of "Major Histocompatibility Complex" they never said, but I'm guessing yes because the result of previous studies mating animals with dissimilar MHC genes resulted in offspring with stronger immune systems.) Women have also been found to find men who are MHC-dissimilar from themselves to be more sexually attractive. Interestingly, women who were on the Pill at the time of the trial tended to select the smell of MHC-similar men as being the most appealing. The researchers' theory as to why this may be is that while MHC-dissimilarity is most beneficial for health of offspring, consistent material support (e.g. food and shelter) during pregnancy and childrearing is also important; because the Pill induces a hormonal state similar to pregnancy, it may be that those women on the Pill were more likely to choose MHC-similar men, such as would occur with a closer genetic relative, as an evolutionary bet on receiving more "familial"-type assistance with childrearing.

Quirks and Quarks can be found here. The episode "Sniffing for Sex" is here.

I've come back to an entry I had thought about but never posted back when we were working on the digestive system. In my previous life as a grad student I was introduced to the idea of fractals, or shapes that appear similar at many different scales. These can be computed mathematically but I don't "do" math so I'll ignore that direction entirely. But what is interesting to me is the natural objects that display this same type of self-similarity. Coastlines are what got me interested because I was doing digital mapping and the generally, but not entirely, irregular shape of a coastline makes it pretty darn difficult to know what scale map you're looking at if there are no other identifying features. Snowflakes and clouds are other common examples of natural objects that display features of being fractal-like. But the best example I think, and one that I've not seen mentioned, is the multi-scale folding in the digestive system that creates all that surface area. If you had only the outline of a cross-section of plicae circularis, villi, and microvilli, I think they'd look pretty much the same. And because the human brain likes patterns, that makes me happy.

I've started reading through the CDC's pink book and it has a *lot* of interesting information on the history and epidemiology of the various diseases and their vaccines.

While waiting for some coil binding to be done at Kinkos I was browsing their display of laminated study guides covering everything from anatomy (the same one that came with our book) to golf short game techniques. I ended up buying a pretty great guide on vitamins and minerals, available online here. It covers daily doses (both in general and disease-specific), food sources, co-vitamins, deficiency symptoms, and toxicity symptoms. The back also has a table listing vitamins and drugs that interact adversely. Not bad for $5, I don't think.