Emergent behavior, features observable at the level of an entire system that cannot be reduced to the description of their smaller parts are a common occurrence in many fields of study. This is true of biology where phase transition has been suggested in the explanation of evolutionary novelties.
Traditional inquiry in the field of biology is split between microbiology, which studies genotypes that define physiological makeup, and macro-biology which concentrates on phenotypes or the typical behavior of specific species. It is assumed for both parts that phenotypes are resultant from the accumulation of micro-changes in genotypes, that have survived environmental constraints. Genotypes and phenotypes are described as discrete units that take small adaptive steps individually from the whole organism. Interconnectivity is viewed as conflicting constraints that may hinder or help evolutionary steps but are otherwise incidental. Microbiology and macrobiology are essentially two different sciences that have a difficult time describing the connecting steps between microscopic and macroscopic. Many macroscopic facts cannot find a convincing explanation from the resultant theory. The idea of continuous and gradual change is incompatible with the observation of certain stable traits in many life forms and the disparate rates of evolution. Comparative morphologists have found that a large number of species share a small number of basic anatomical design, baupläne, that differentiate various animal phyla. All these baupläne have appeared suddenly in the Cambrian Explosion, shortly after the appearance of multicellular organisms, 500 million years ago[3].
Many vestiges are still present long after the functional usefulness have gone. Somehow they have escape natural selection. Embryos of birds and mammals still have gill arches, a feature that has not been in use for 400 million years. Other evolution features, such as sexual reproduction, are puzzling. It is an expensive feature providing only half of the fitness that asexual reproduction provides; asexual reproduction has not proven to be an inferior strategy for the propagation of specific genotypes [17]. It does not explain why there are, for example, specialized flies that have evolved within a thousand years in the presence of non-indigenous banana crops in Hawaii, and why biological structures such as snapping turtles and alligators have changed little since they first appeared hundreds of million years ago. Fossil examination does not agree with the gradual evolution theory. Eldredge and Gould have showed, in 1972, that morphological characters are stable for long periods of time and dramatic changes occur in short bursts.
These observations are reminiscent of emergent feature theory developed in statistical physics. Sudden changes in the state variable of a physical system that give rise to emergent features are well understood phenomena in statistical mechanics. However this particular approach is not widely used in the description of evolutionary steps. Kaufman [38] and a few others are suggesting that many of these incongruities in empirical facts can be described using models of multi-bodied systems.