This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Evolution of a natural gene network explored by Yale researchers Journal information: Nature In this research effort, the team looked at historical contingency—where a sequence of events led to a present state in a biological context. In ordinary life, historical contingencies occur all the time, looking over the life a person has lived, for example, would reveal many such instances, where decisions were made that led to a new state, and where another decision was eventually made based on what had occurred thus far, and on and on—mapping historical contingencies over time leads to what is known as a regulatory network—a depiction that illustrates the impact of all the contingencies that have occurred. In the biological sciences historical contingencies apply to evolutionary changes that occur over a certain period of time, and the regulatory network allows researchers to see which changes were contingent on which prior changes. Such work is challenging, which is why the researchers chose brewer’s yeast to study—not only does it have a reasonably simple genome, as New and Lehner, point out, but there are also genetic engineering tools that have been developed for its study that can be adapted for use across more than one species.Studying historical contingency in organisms works because of the way genetics works—as a trait evolves, the genome changes. Also, sometimes, changes that occur are lost due to changes in the environment, but the genome retains some of the DNA that came about due to the original change, and that too can be used in creating a regulatory network. In this new work, the researches reconstructed the evolutionary path of two mating types in brewer’s yeast, dubbed “a” and “α”—both cause genes to be switched on when exposed to pheromones. As part of their analysis they were able to show the evolutionary path that the types took as each was impacted by events, leading to contingencies and thus were able to construct a regularity network. They were also able to show, as New and Lehner, note that understanding the evolution of individual genes must involve the evolution of regulatory networks.