Most animals reproduce sexually. This means that every individual has to find another individual to mate with – and they have to convince that other that they’re worthy of the privilege. More often than not when it comes to picking that special someone, it’s the girls that get to be choosy. Females spend a lot more energy per offspring than males from the get-go due to the size of our eggs (let alone most child rearing responsibilities), so as a gender, females want to make sure they don’t waste their efforts. To ensure top notch kids, females choose the best male they can find. It’s no wonder that male animals have all kinds of ways of advertising that they’re #1 – from showy feathers to intricate dances or even deadly fights.
Of course, it’s not like the decision is final. In humans, we know all too well that even after commitments are made, women compare their man to other guys. They feel proud when he proves himself to be the best, and disappointed (or worse, pick a new man) when he falls short of his peers. But what about animals? Do animals feel the pang of regret when they realize they could have done better? Or satisfied with themselves when they’ve chosen the best of the bunch?
They do, according to new research coming out of the Department of Biology at Stanford University. Scientists had ready-to-mate female African cichlid fish (Astatotilapia burtoni) pick a mate from two potential male suitors. Once she’d made her decision, they had her watch fights between the two: sometimes her man would win, other times, he would lose.
Since we can’t ask a fish how she’s feeling, what the scientists wanted to know was how her brain reacted to each scenario. Certain regions of the vertebrate brain, collectively called the Social Brain Network (SBN), have been shown to have higher activity in response to social information. . The lateral septum, for example, becomes more active when animals are anxious, nervous or upset, while other areas, like the preoptic area, fire in response to reproductive stimuli. Since we don’t have MRI machines for small fish, the researchers instead looked at the expression of immediate early genes (precursors to signaling cascades and other genes which turn on when neurons are activated) as a proxy for brain activity in different areas of the SBN.
The results were dramatic. When a female fish watched the man she chose lose, the lateral septum saw large increases in expression. Meanwhile, when she saw him win, other areas fired just as strongly.
These results strongly suggest that just seeing social interactions between males can alter gene expression in a female’s brain, affecting how she feels. While these results aren’t shocking when we consider that picking the right mate is very important evolutionarily and thus reacting to information about mate quality would be highly advantageous, this study is one of only a handful to show that animal’s brains directly respond to social information at a genetic level. This kind of information may help scientists understand how the brain processes social information, even in very distantly related animals like ourselves.
Citation: Desjardins, J., Klausner, J., & Fernald, R. (2010). Female genomic response to mate information Proceedings of the National Academy of Sciences, 107 (49), 21176-21180 DOI: 10.1073/pnas.1010442107