Blackwell Publishing

Molecular evolution and neutral theory - Why is molecular evolution constant?


Living fossils

Of particular interest to the neutralist debate is the study of living fossils.

A living fossil is a species that closely resembles its fossil ancestors. It is a lineage which has undergone a long period of stasis. A famous example of this is the coelecanth pictured opposite - there are fossils over 300 million years old that are very similar to the modern species.

Two conjectures about why these groups have changed so little:

• Stabilizing selection. Some living fossil species live in relatively isolated habitats, with no apparent competitors; and if their habitats have been stable there will have been no pressure for them to change.

• Absence of genetic variation. However, there is no evidence that living fossils have peculiar genetic systems that might prevent evolutionary change. The amount of protein polymorphism in modern living fossils has been measured by gel electrophoresis and is not noticeably low.

Molecular evolution in living fossils provides a striking example of the independence between molecular and morphological evolution.

Previous Next