User:Jaspergeli/Living fossil
From Wikipedia, the free encyclopedia
A living fossil is an extant taxon that closely resembles organisms otherwise known only from the fossil record. As a rule, to be considered a living fossil, the fossil species must be old relative to the time of origin of the extant clade. Living fossils commonly are species-poor lineages, but they need not be. The term living fossil is not formally defined, but in the scientific literature, the term usually connotes a bradytelic group. "Bradytely", however, is rarely used in the modern scientific literature but the characteristic of a bradytelic group is that its changes fluctuate on a small scale and do not accumulate over time. In modern literature, the term most often used for that distinctive evolutionary tempo is "stasis". Living fossils exhibit stasis over geologically long timescales.
In popular literature "living fossil" commonly embodies radical misunderstandings such as that the organism somehow has undergone no significant evolution since fossil times, with practically no molecular evolution or morphological, but scientific investigations have repeatedly discredited any such claims about molecular evolution. An important misunderstanding underlying the idea that living fossils do not evolve is that stabilizing selection is an evolutionary process, perhaps even the dominant one in morphological evolution.