title: Evolution of lifespan.
abstract: Present-day evolutionary theory, modern synthesis and evo-devo, appear to explain evolution. There remain however several points of contention. These include: biological time, direction, macroevolution verses microevolution, ageing and the extent of internal as opposed to external mediation. A new theoretical model for the control of biological time in vertebrates/bilaterians is introduced. Rather than biological time being controlled solely by a molecular cascade domino effect, it is suggested there is also an intracellular oscillatory clock. This clock (life's timekeeper) is synchronised across all cells in an organism and runs at a constant frequency throughout life. Slower frequencies extend lifespan, increase body/brain size and advance behaviour. They also create a time void which could aid additional evolutionary change. Faster frequencies shorten lifespan, reduce body/brain size and diminish behaviour. They are therefore less likely to mediate evolution in vertebrates/mammals. It is concluded that in vertebrates, especially mammals, there is a direction in evolution towards longer lifespan/advanced behaviour. Lifespan extension could equate with macroevolution and subsequent modifications with microevolution. As life's timekeeper controls the rate of ageing it constitutes a new genetic theory of ageing. Finally, as lifespan extension is internally mediated, this suggests a major role for internal mediation in evolution.
authors.affiliation: University of Newcastle, Wear Base Unit, Monkwearmouth Hospital, Newcastle Road, Sunderland SR5 1NB, UK. Electronic address: david.neill@ncl.ac.uk.
authors.forename: David
authors.initials: D
authors.lastname: Neill
mesh_terms: D000818:Animals; D005075:Biological Evolution; D006801:Humans; D008017:Life Expectancy
keywords: Cope׳s rule; Domino effect; Evo-devo; Heterochrony; Life׳s timekeeper