Mosaic evolution (or modular evolution) is the idea that evolutionary change takes place in some body parts or systems without simultaneous changes in other parts. Another definition is the "evolution of characters at various rates both within and between species".408 Its place in evolutionary theory comes under long-term trends or macroevolution.
Evolution from a basal (early) form to a derived (later) form takes place in stages. Modules (groups of characters) change semi-independently of each other. They change at different times, so producing a mosaic of primitive and derived traits.
By its very nature, the evidence for this idea comes mainly from palaeontology. It is not claimed that this pattern is universal, but there are now a wide range of examples from many different taxa. Some examples:
- Human evolution. The early evolution of bipedalism in Australopithecines, and its modification of the pelvic girdle took place long before there was any significant change in the skull, or brain size.
- Archaeopteryx. Nearly 150 years ago Thomas Henry Huxley compared Archaeopteryx with a small theropod dinosaur, Compsognathus. These two fossils came from the Solnhofen limestone in Bavaria. He showed that the two were very similar, except for the front limbs and feathers of Archaeopteryx. Huxley's interest was in the basic affinity of birds and reptiles, which he united as the Sauropsida. The interest here is that the rest of the skeleton had not changed.
- Meadow voles during the last 500,000 years.
- The pterosaur Darwinopterus. The type species, D. modularis was the first known pterosaur to display features of both long-tailed (rhamphorhynchoid) and short-tailed (pterodactyloid) pterosaurs.
- Evolution of the horse. The major changes took place at different times, not all simultaneously.
Related pages [change]
- Gene regulation
- Parallel evolution
- Convergent evolution
- Transitional fossil
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