What is parallel evolution? Please give an example.

Parallel evolution refers to a process where two related species or two groups of organisms evolve in a similar way over a period of time despite being in different geographical locations or ecological niches. This phenomenon occurs because the species in question are subject to similar selective pressures, which drive them to develop analogous structures or adaptations that are not due to a recent common ancestry but rather due to similar environmental challenges.

An example of parallel evolution can be seen in the marsupial mammals of Australia and the placental mammals found elsewhere. Despite being separated by vast geographical distances and having different reproductive strategies (marsupials give birth to relatively undeveloped young that often complete their development in a pouch, while placentals give birth to more fully developed young), some marsupials have evolved to fill similar ecological niches to those filled by placental mammals, resulting in a remarkable resemblance in form and function.

One specific example is the comparison between the Tasmanian wolf (Thylacinus cynocephalus), a marsupial, and the placental canids such as wolves and dogs. Both developed similar body shapes, sharp teeth, and hunting strategies to catch and eat similar prey, despite their last common ancestor being very distant in the evolutionary past. The Tasmanian wolf, or thylacine, had a head and body shape remarkably similar to that of true wolves and other large canids, even though it was not closely related to them.

This convergence in traits is a result of parallel evolution, where unrelated species independently evolve similar adaptations to cope with comparable environmental and ecological demands.