But whose survival is natural selection concerned with? Is it the survival of the individual? Of the species? Of the habitat or ecosystem? These three - individual, species, habitat - are not necessarily compatible or mutually reinforcing in their goals and actions.
To prevent the potential excesses of egotistic self-propagation, survival is self-limiting and self-regulating. Consider epidemics: rather than go on forever, they abate after a certain number of hosts have been infected. It is a kind of Nash equilibrium. Macroevolution (the coordinated emergence of entire groups of organisms) trumps microevolution (the selective dynamics of species, races, and subspecies) every time.
This delicate and self-correcting balance between the needs and pressures of competing populations is manifest even in the single organism or species. Different parts of the phenotype invariably develop at different rates, thus preventing an all-out scramble for resources and maladaptive changes. This is known as "mosaic evolution". It is reminiscent of the "invisible hand of the market" that allegedly allocates resources optimally among various players and agents.
Moreover, evolution favors organisms whose rate of reproduction is such that their populations expand to no more than the number of individuals that the habitat can support (the habitat's carrying capacity). These are called K-selection species, or K-strategists and are considered the poster children of adaptation.
First published here: