The Scientist and Jerome Siegel | Mar 1, 2016 | 10+ min read
Once believed to be unique to birds and mammals, sleep is found across the metazoan kingdom. Some animals, it seems, can’t live without it, though no one knows exactly why.
Sexual selection doesn’t end when females choose a mate. Females and males of many animal species employ an array of tactics to stack the deck in their reproductive favor.
UPSIDE-DOWN MITO-MAPLE:Courtesy of Douglas C. WallaceResearchers constructed a phylogenetic tree based upon human mitochondrial DNA (mtDNA) variation. A branch bifurcates whenever they found an additional polymorphism. At the top of the inverted tree is mitochondrial "Eve"; the illustration shows two mtDNA sub-branches, or lineages, found in Europe and the Middle East. The J1- and J2-branch polymorphisms in the cytochrome b gene might have spread because they were climatically advantageous. (Rep