Roberts RG (2015) The Fitness Effects of Love. PLoS Biol 13(9): e1002249. doi:10.1371/journal.pbio.1002249. September 14, 2015.

“Humans are a mostly monogamous species—a large proportion of us choose mates with whom we spend long periods of time, and many of us produce children through sexual reproduction with those mates. We tend to think of our choice of mate as being very specific—the result of a long and judicious screening process involving nervous flirtations, set-ups by friends, online matchmaking sites, awkward dates, humiliating rejections, hasty retreats, and the occasional lucky strike. The eventual relationship, after whittling down a cast of thousands, is founded on love, and can be a thing of wonder. But we are also biological entities, subject to the cruel pressures of natural selection—isn’t this choosiness rather a costly waste of time and energy when we should be just “going forth and multiplying?” Naively, perhaps if we somehow end up selecting the genetically “best” mates, then choosiness might pay off, but not everyone can end up with the “best,” and much of the time our choices can seem, frankly, rather idiosyncratic (“What on earth does she see in him?”). What, if anything, is the evolutionary point of it all? Doing a cost/benefit analysis of love is a challenging business, with many potential confounds, and—in the case of humans—some ethical constraints with regard to the possibilities of experimentation. A new study published in PLOS Biology by Malika Ihle, Bart Kempenaers, and Wolfgang Forstmeier attempts to use a model animal in an elegant experiment designed to tease apart the reproductive consequences of mate choice. The authors took advantage of the fact that the zebra finch (Taeniopygia guttata, a native bird of Australia) shares many characteristics with humans, mating monogamously for life and sharing the burden of parental care. It was already known that the female finches choose mates in a way that is specific to the individual, and there is little consensus among females as to who is the cutest male.”