Polyfyletiska

Polyfyletiska refers to a grouping of organisms that do not share a recent common ancestor. In the study of phylogenetics, which aims to understand the evolutionary relationships between species, a polyphyletic group is considered artificial because its members have evolved independently from different ancestral lineages. This contrasts with monophyletic groups, which include all descendants of a common ancestor, and paraphyletic groups, which include a common ancestor and some but not all of its descendants.

The identification of polyphyletic groups often arises from convergent evolution, where unrelated organisms evolve similar traits due to similar environmental pressures or lifestyles. For example, the traditional grouping of "warm-blooded animals" was considered polyphyletic because birds and mammals, while both warm-blooded, evolved this characteristic independently. Similarly, the grouping of marine animals like dolphins (mammals) and fish (a diverse group of aquatic vertebrates) would be polyphyletic as they do not share a direct, recent common ancestor that is not also an ancestor to other land vertebrates.

Modern phylogenetic analyses, particularly those using molecular data like DNA sequences, are crucial for accurately identifying polyphyletic groups and establishing more natural, evolutionary meaningful classifications. Recognizing polyphyletic groups helps scientists avoid misconceptions about evolutionary history and refine our understanding of the tree of life.