Editing Paraphyly (section)

=== In cladistics ===

{{further|Cladistics}}

Groups that include all the descendants of a common ancestor are said to be ''[[monophyletic]]''. A paraphyletic group is a monophyletic group from which one or more subsidiary [[clade]]s (monophyletic groups) are excluded to form a separate group. Philosopher of science Marc Ereshefsky has argued that paraphyletic taxa are the result of [[anagenesis]] in the excluded group or groups.<ref>{{cite book|url=https://books.google.com/books?id=ucilIjrex5cC&pg=PA9 |title=Handbook of Plant Science|isbn=978-0-470-05723-0|last1=Roberts|first1=Keith|date=10 December 2007|publisher=John Wiley & Sons }}</ref> A cladistic approach normally does not grant paraphyletic assemblages the status of "groups", nor does it reify them with explanations, as in cladistics they are not seen as the actual products of evolutionary events.<ref>{{Cite book |last=Williams |first=David M. |title=Cladistics: A Guide to Biological Classification |last2=Ebach |first2=Malte C. |date=2020-08-06 |publisher=Cambridge University Press |isbn=978-1-108-88267-5 |language=en}}</ref>

A group whose identifying features evolved [[Convergent evolution|convergently]] in two or more lineages is ''[[polyphyletic]]'' (Greek πολύς [''polys''], "many"). More broadly, any taxon that is not paraphyletic or monophyletic can be called polyphyletic. Empirically, the distinction between polyphyletic groups and paraphyletic groups is rather arbitrary, since the character states of common ancestors are inferences, not observations.{{citation needed|date=April 2023}}

These terms were developed during the debates of the 1960s and 1970s accompanying the rise of [[cladistics]].

Paraphyletic groupings are considered problematic by many taxonomists, as it is not possible to talk precisely about their phylogenetic relationships, their characteristic traits and literal extinction.<ref>{{Cite book|url=https://books.google.com/books?id=XcYSZTPkXTQC&pg=PA166 |title=The Symbolic Species Evolved |last1=Schilhab |first1=Theresa |last2=Stjernfelt |first2=Frederik |last3=Deacon |first3=Terrence |year=2012 |publisher=Springer |isbn=978-94-007-2335-1}}</ref><ref name="Villmoare-2018">{{Cite journal |last=Villmoare |first=Brian |date=2018 |title=Early ''Homo'' and the role of the genus in paleoanthropology |journal=American Journal of Physical Anthropology |volume=165 |pages=72–89 |doi=10.1002/ajpa.23387|pmid=29380889 |doi-access=free }}</ref> Related terms are [[Crown group#stem group|stem group]], [[chronospecies]], budding cladogenesis, anagenesis, or [[Evolutionary grade|'grade']] groupings. Paraphyletic groups are often relics from outdated hypotheses of phylogenic relationships from before the rise of cladistics.<ref>{{cite journal |last1=Dominguez |first1=Eduardo |last2=Wheeler |first2=Quentin D. |date=1997 |title=Forum – Taxonomic Stability is Ignorance |journal=Cladistics |volume=13 |issue=4 |pages=367–372 |doi=10.1111/j.1096-0031.1997.tb00325.x|pmid=34911226 |s2cid=55540349 |doi-access=free }}</ref>