What factors predominate in evolution? In daily life, the constant evolution of our lives is influenced by our conditions and by external factors. If I want to build a house with my own hands, I have to consider my abilities, some of which are genetic (I am small, thin and I am not strong, so I can’t carry heavy materials), and also I have to check how many money I can spend; hence, the “evolution” of the house, sort of, depends on both factors.
Two hypothesis, the “Red Queen” and the “Court Jester”, view evolution in these terms . The Red Queen hypothesis view evolution as a balance of biotic (intrinsic) pressures, whereas the Court Jester model propose that evolution, speciation and extinction rarely happen except in response to unpredictable changes in the physical environment. Finally, it seems reasonable that evolution proceeds as a mixture of both models, where the Court Jester model operates in a time scale far longer than the Red Queen. Locally, in an ecological niche, the competition (biotic factor) between events en species shapes the local evolution, but in a larger scale, such as earthquakes, rise of mountains, and separation of physical spaces, provide a definitive barrier shaping long-term evolution, although events such as migration in birds and migration between continents should be taken into account.
The Court Jester model seems more logical to be imagined. Darwin viewed evolution in terms of biotic factors, but in his journeys, he observed marked differences in similar species in long distances, being islands a hallmark of evolutionary observation. But the Red Queen hypothesis, in biological terms, remained a challenge to be resolved in a laboratory. In a recent paper published in Nature , Paterson and coworkers provided a genetic evidence for the Red Queen hypothesis, using a smart experimental design. They used co-cultures of the bacterium Pseudomonas fluorescens and its viral phage Φ2. The molecular evolution rate in the phage was higher when both bacterium and phage coevolved with each other that when phage evolved against a constant host genotype. Remarkably, the genes that most rapidly evolved were involved in host infection, after 12 serial transfers (being each transfer every 48 hours). Consequently, coevolved phage populations varied in the range and identity of host genotypes that they were able to infect, but phage from evolved populations failed to infect any coevolved hosts.
How fast a bacterium can coevolve inside a human organism? For example, in a hospital, there is a spreading of infectious bacteria. Could be possible a coevolution of the microorganism with its host, allowing the mutation and adaptation of the bacteria in order to be able to infect more hosts? It will be interesting the extrapolation of the findings from Paterson and coworkers, at the clinical level. An example is provided by a brief review in PLoS Genetics . Neisseria meningitidis, a major cause of morbidity and mortality in childhood, in a lapse of three decades of observation showed little variation, but a few loci showed variation, including the gene coding for a transferrin binding protein (tbpB). However, it seems that the genetic variation occurs at expenses of the “transmission fitness”. It will be interesting to see if this technique can be improved to study more complex and bigger “cosmos” and specially for disease-causing bacterium, or viruses.
 Benton MJ (2009). The Red Queen and the Court Jester: species diversity and the role of biotic and abiotic factors through time. Science (New York, N.Y.), 323 (5915), 728-32 PMID: 19197051
 Paterson S, Vogwill T, Buckling A, Benmayor R, Spiers AJ, Thomson NR, Quail M, Smith F, Walker D, Libberton B, Fenton A, Hall N, & Brockhurst MA (2010). Antagonistic coevolution accelerates molecular evolution. Nature, 464 (7286), 275-8 PMID: 20182425
 Falush D (2009). Toward the use of genomics to study microevolutionary change in bacteria. PLoS genetics, 5 (10) PMID: 19855823