Thursday, September 27, 2012

Darwin’s bridge between microevolution and macroevolution

Darwin on the link between micro- and macroevolution
On the Origin of Species Chapter 4

Another GEDNA bookmark  Darwin’s bridge between microevolution and macroevolution
(reading the article requires on-line registration with Nature)
Evolutionary biologists have long sought to understand the relationship between microevolution (adaptation), which can be observed both in nature and in the laboratory, and macroevolution (speciation and the origin of the divisions of the taxonomic hierarchy above the species level, and the development of complex organs), which cannot be witnessed because it occurs over intervals that far exceed the human lifespan. The connection between these processes is also a major source of conflict between science and religious belief. Biologists often forget that Charles Darwin offered a way of resolving this issue, and his proposal is ripe for re-evaluation in the light of recent research.

The keys to Darwin’s thinking about macroevolution are the ‘principle of divergence’ and extinction. In this Review, we consider how these principles have fared since the publication of On the Origin of Species1, and we discuss whether Darwin’s concept of the relationship between microevolution and macro evolution can provide useful insight today. This relationship continues to generate controversy both within the biological sciences and in the confrontation between science and religion. On the 200th anniversary of Darwin’s birth, a status report is surely in order.
David N. Reznick & Robert E. Ricklefs
Nature 457, 837-842 (12 February 2009)
I warmly recommended this article in which two American biologists argue that Darwin's On the Origins of Species 1859 is still today a source of fresh insights worth of serious consideration by modern scientists. The paper focuses especially on his theory about divergence and extinction.

On divergence
Analyses of diversification sometimes reveal other details that are consistent with Darwin’s macroevolution theory. For example, the passerine birds include many depauperate lineages that occupy ecologically or geographically marginal habitats40,41. These lineages seem to have diversification and extinction rates that are an order of magnitude lower than those of more species-rich clades of passerines, and thus cor respond to Darwin’s lineage F (Fig. 1), a slowly diversifying lineage isolated from interactions with more rapidly diversifying lineages. Certainly, Darwin’s principle of divergence has been supported by a range of what are now well-characterized and generally accepted evolutionary phenomena.
op.cit. p. 840

On extinction
Darwin’s proposal for the cause of extinction has yet to be fairly evaluated. He suggested that many taxa are driven to extinction by competition from ecologically similar but adaptively superior groups undergoing diversification.

This core assumption of Darwin’s explanation for macroevolution has little empirical support, mainly because the search for appropriate evidence has fallen through the gap between evolution and ecology; of course, pertinent evidence would strongly resist discovery under any circumstance.
op.cit. p. 841

Evolution and Ecology!
So after 150 years of intensive research there is still serious work to be done on this major issue - the origins of species - raised by Charles Darwin's amazing study On the Origins of Species!