How do complex behaviors evolve?

How do Complex Behaviors evolve? Which of these houses would you build? Why is it that you would pick that house and someone else might pick another? Certainly there are the type of house you grew up in, your cultural history, and your life experiences play a role, but could it also be genetic? Researchers at Harvard University are investigating this question in mice. Field mice and deer mice build distinctly different types of homes. Whereas the deer mouse will make a very simple burrow, the field mouse always digs a longer entrance tunnel and builds an excape tunnel (a tunnel that nears the surface but does not go through). burrow burrow escape tunnel short entrance long entrance funnel tunnel Deer Mouse Field Mouse What happens when these different types of burrowers are bred together? Offspring in the first generation make burrows that exactly imitate the burrows of the original field mice, indicating that genes for burrow length and shape seem to be dominant in the field mouse. To observe the recessive phenotype, the researchers then bred this hybrid offsprind with the original deer mouse. This second generation of offspring showed a wide variety of burrow phenotypes: shorter tunnel shorter tunnel NO escape tunnel longer tunnel escape tunnel longer tunnel NO escape tunnel escape tunnel The tunnels vary in length between the extremes of the original two species of mice, indicating that this behavior may be dependent on several different genes. The presence of the escape tunnel, however, appears to be an all-or-nothing phenomenon, which suggests that it may depend upon a single allele. Furthermore, almost exactly half (46%) of these second generation mice built escape tunnels, which is precisely what would be predicted to occur if the behavior is determined by a single dominant allele. Recent advances in molecular genetics allowed the researchers to validate these hypotheses. By genotyping all of the mice studied and using quantitative methods to compare the genomes, the researchers were able to identify specific genetic loci correlated with the tunneling traits of the mice. As expected, three loci were correlated to the tunnel length, and a single genetic locus was linked to the presence of an escape tunnel. Interestingly, some of these genes appear to also be linked to addictive behaviours. As XX researcher Hopi Hoekstra put it, "When you watch one of these mice, you can't help but think they're addicted to burrowing!" What's the big deal? - Suggests that the genetic basis of complex behaviours may be modular. That is, they may be composed of simpler behaviours with a direct genetic basis. One of the first experiment to use modern genetic techniques to explain a behavioral phenomenon. Opens up the possibility for many more genetic experiments in wild animal strains instead of the usual laboratory animals. Sources: Weber, J.N., B.K. Peterson and H.E. Hoekstra. 2013. Discrete genetic modules are responsible for the evolution of complex burrowing behaviour in deer mice. Nature 493:402-405 http://www.nature.com/multimedia/podcast/nature/v493/n7432/nature-2013-01-17.mp3 http://news.sciencemag.org/sciencenow/2013/01/building-a-better-burrow.html?ref=hp