Prettier Female Great Tits Produce Healthier Hatchlings

Good looks aren't an accident. Well, in the sense of mutations being genetic accidents they are, but appearance is something selected for by evolution, just like anything else that makes you you. Sometimes, the male of a particular species is more attracted to a female (or vice versa) based on how the female looks, or whether or not that female looks "good." And things that appear attractive should be correlated to genetic fitness. If it were otherwise, then it would be good-looking, not genetically healthy mothers having offspring less prone to survival. That's not how evolution works.

A new study bears this idea out. Normally, I wouldn't quote a press release like this, but it's possible that some readers might also have the sense of humor of a 14-year-old American male: "A female great tits' (Parus major) appearance is shown to signal healthy attributes in offspring in a paper in BioMed Central's open access journal Frontiers in Zoology." In other words, better-looking great tits (a small, yellow variety of songbird) have healthier chicks. That's an important finding: physical perfection is selected for.

Quickly, here's how the study worked. Researchers separated chicks from their genetic mothers, handing them off to foster mother-birds that raised them instead. The long-term health of the chicks was then evaluated against different characteristics of the different mothers. What they found was that the immune system strength of the baby birds was tied to the "immaculateness" of the white spot on both the foster and genetic mothers' cheeks. The weight of the chicks was correlated to the size of the black stripe on the chest of the genetic mother, while the body size of the chicks was tied only to the body size of the genetic mother.

The pair responsible for the new research, Vladimír Remeš and Beata Matysioková, explain: "Bigger healthier babies are important to the reproductive success of individuals, because they are more likely to survive to adulthood - so it is useful for birds to be able to work out which potential mates will produce the best babies. Maintaining bright coloration uses up resources which could otherwise be invested in reproduction or self-maintenance - consequently the evolution and maintenance of ornamentation in female great tits is probably due to direct selection by males."

It's interesting to consider how we humans have scrambled this, particularly in our most recent history of breeding. There is "conventional attractiveness" in our culture, but arguably conventional attractiveness linked to health and survival, in particular weight attributes, has been horribly skewed by the media and fashion industries. So, what happens after a large enough amount of time of culture steering the health of a species in the wrong direction? Can evolutionary survival steer it back?

Though, those are probably theoretical questions at this point in evolution, where the entire human genome has been successfully mapped and a wide variety of unhealthy conditions are routinely tested for while babies are still abortable clumps of cells. One can imagine a future where selection is even overprecise: songbirds meet Gattaca, a world of super-babies lacking the genetic variation to adapt at all. 

Reach this writer at michaelb@motherboard.tv.