Uppose that genetic drift in a population of salamanders results in color differences across the population's range. Over time, some salanders become primarily brown, whereas other salamanders become mottled brown with black. Individuals from each group occasionally interbreed. Within each population, there is no genetically‑based preference for mating with a brown salamander or a mottled salamander. This scenario represents what kind of evolution?

Which of the following best describes the expensive tissue hypothesis? brains require more energy, so the gut had to be reduced, and larger brains and tool use led to higher quality diets. increasing body size means that homo neanderthalensis had to include more fat in its diet. brains require more energy, so the gut had to be reduced as brains got bigger. brains require more fat, so the gastrointestinal viscera (gut) had to expand, and hands were needed to acquire more food.