at 38°C; Predatory lines – for a short time to catch live crickets; Herbivorous lines – for capability to maintain body mass when fed a low-quality diet “diluted” with dried, powdered grass. Four replicate lines are maintained for each of the three selection directions and another four as unselected Controls. After approximately 20 generations of selective breeding, voles from the Aerobic lines evolved a 60% higher swim-induced metabolic rate than voles from the unselected Control lines. Although the selection protocol does not impose a thermoregulatory burden, both the basal metabolic rate and thermogenic capacity increased in the Aerobic lines. Thus, the results have provided some support for the “aerobic capacity model” for the evolution of endothermy in mammals. More than 85% of the Predatory voles capture the crickets, compared to only about 15% of unselected Control voles, and they catch the crickets faster. The increased predatory behavior is associated with a more proactive coping style (“personality”). During the test with low-quality diet, the Herbivorous voles lose approximately 2 grams less mass (approximately 10% of the original body mass) than the Control ones. The Herbivorous voles have an altered composition of the bacterial microbiome in their caecum. Thus, the selection has resulted in evolution of the entire holobiome, and the experiment may offer a laboratory model of hologenome evolution. Synthetic biology Synthetic biology offers unique opportunities for experimental evolution, facilitating the interpretation of evolutionary changes by inserting genetic modules into host genomes and applying selection specifically targeting such modules. Synthetic biological circuits inserted into the genome of Escherichia coli or the budding yeast Saccharomyces cerevisiae degrade (lose function) during laboratory evolution. With appropriate selection, mechanisms underlying the evolutionary regain of lost biological function can be studied. Experimental evolution of mammalian cells harboring synthetic gene circuits reveals the role of cellular heterogeneity in the evolution of drug resistance, with implications for chemotherapy resistance of cancer cells. Other examples Stickleback fish have both marine and freshwater species, the freshwater species evolving since the last ice age. Freshwater species can survive colder temperatures. Scientists tested to see if they could reproduce this evolution of cold-tolerance by keeping marine sticklebacks in cold freshwater. It took the marine sticklebacks only three generations to evolve to match the 2.5 degree Celsius improvement in cold-tolerance found in wild freshwater sticklebacks. Microbial cells and recently mammalian cells are evolved under nutrient limiting conditions to study their metabolic response and