The Zero-Force Evolutionary Law (ZFEL) is a theory proposed by Daniel McShea and Robert Brandon regarding the evolution of

diversity Diversity, diversify, or diverse may refer to: Business *Diversity (business), the inclusion of people of different identities (ethnicity, gender, age) in the workforce *Diversity marketing, marketing communication targeting diverse customers * ...

and

complexity Complexity characterizes the behavior of a system or model whose components interact in multiple ways and follow local rules, leading to non-linearity, randomness, collective dynamics, hierarchy, and emergence. The term is generally used to c ...

. Under the ZFEL, diversity is understood as the variation among organisms and complexity as the variation among the parts within an organism. A part is understood as a system that is to some degree internally integrated and isolated from its surroundings.{{cite book , last1=McShea, first1=D. W., last2=Venit, first2=E. P., chapter=What is a part? , pages=259–284 , editor=Günter P. Wagner , title=The Character Concept in Evolutionary Biology, date=2001 , doi=10.1016/B978-012730055-9/50022-7 , isbn=9780127300559 In a multicellular organism, for example, a cell is a part, and therefore complexity is the number of different cell types. Like the

theory of relativity The theory of relativity usually encompasses two interrelated physics theories by Albert Einstein: special relativity and general relativity, proposed and published in 1905 and 1915, respectively. Special relativity applies to all physical ph ...

, the theory has a special and general formulation. The special formulation states that in the absence of natural selection, an evolutionary system with variation and

heredity Heredity, also called inheritance or biological inheritance, is the passing on of traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic infor ...

will tend spontaneously to diversify and complexify. The general formulation states that evolutionary systems have a tendency to diversify and complexify, but that these processes may be amplified or constrained by other forces, including natural selection. The mechanism of the ZFEL is the inherently error-prone process of replication and reproduction. In the absence of selection, errors tend to accumulate, with the result that individuals within a population tend to become more different from each other (diversity) and parts within an individual tend to become more different from each other (complexity). Both of these tendencies can be overcome by selection, including stabilizing or negative selection, with the result that diversity or complexity often does not change, or even decreases. What the ZFEL offers is not so much a prediction as a null expectation, telling us what will happen in evolution when selection is absent. It is the analogue of Newton's law of momentum, which tells us the trajectory of a moving object in the absence of forces (a straight line).

References

Evolutionary biology Neutral theory

See also

References