Primitive (phylogenetics)

In phylogenetics, a primitive (or ancestral) character, trait, or feature of a lineage or taxon is one that is inherited from the common ancestor of a clade (or clade group) and has undergone little change since. Conversely, a trait that appears within the clade group (that is, is present in any subgroup within the clade but not all) is called advanced or derived. A clade is a group of organisms that consists of a common ancestor and all its lineal descendants.

A primitive trait is the original condition of that trait in the common ancestor; advanced indicates a notable change from the original condition. These terms in biology contain no judgement about the sophistication, superiority, value or adaptiveness of the named trait. "Primitive" in biology means only that the character appeared first in the common ancestor of a clade group and has been passed on largely intact to more recent members of the clade. "Advanced" means the character has evolved within a later subgroup of the clade.

Phylogenetics is utilized to determine evolutionary relationships and relatedness, to ultimately depict accurate evolutionary lineages. Evolutionary relatedness between living species can be connected by descent from common ancestry.[1] These evolutionary lineages can thereby be portrayed through a phylogenetic tree, or cladogram, where varying relatedness amongst species is evidently depicted. Through this tree, organisms can be categorized by divergence from the common ancestor, and primitive characters, to clades of organisms with shared derived character states. Furthermore, cladograms allow researchers to view the changes and evolutionary alterations occurring in a species over time as they move from primitive characters to varying derived character states.[2]

Cladograms are important for scientists as they allow them to classify and hypothesize the origin and future of organisms. Cladograms allow scientists to propose their evolutionary scenarios about the lineage from a primitive trait to a derived one. By understanding how the trait came to be, scientists can hypothesize the environment that specific organism was in and how that affected the evolutionary adaptations of the trait that came to be.[3]

Other, more technical, terms for these two conditions—for example, "plesiomorphic" and "synapomorphic"—are frequently encountered; see the table below.

  1. ^ Baum, David A.; Stacey D. Smith (2012). Tree thinking: an introduction to phylogenetic biology. Greenwood Village, CO: Roberts. ISBN 978-1-936221-16-5. OCLC 767565978.
  2. ^ E. O. Wiley; Bruce S. Lieberman (2011). Phylogenetics: theory and practice of phylogenetic systematics (2nd ed.). Hoboken, NJ: Wiley-Blackwell. ISBN 978-1-118-01786-9. OCLC 715182861.
  3. ^ V., Kardong, Kenneth. Vertebrates : comparative anatomy, function, evolution (Seventh edition ed.). New York, NY. ISBN 9780078023026. OCLC 862149184