John Tower’s preprint proposes a model linking adaptation to aging and sexual conflict
John Tower’s preprint proposes a model linking adaptation to aging and sexual conflict
On September 7, University of Southern California biologist John Tower posted a bioRxiv preprint, a preliminary scientific paper that has yet to undergo peer review. It describes when a regulated change of state can provide an immediate benefit while carrying a later cost.
A cell needs to preserve functional configurations, from DNA to proteins, but its environment sometimes demands a different response. Tower’s model distinguishes passive errors from active destabilization: a regulated departure from a maintained state. Such a transition is worthwhile if, as the environment changes, it leads to a beneficial new state often enough and at an acceptable cost. Selection can then favor both accurate cellular maintenance and a switching mechanism.
A hypothetical complex made of components A and B illustrates this. Degradation of B destroys the AB complex but releases A, which can bind to AB to form a more efficient AAB complex. A local loss gives the system a route to another state.
In another model, faster degradation and synthesis of a factor leave the proportions of states at a given moment unchanged but reduce dependence on the previous state more quickly. The model therefore accounts for the current proportions of states, the direction of the transition, and memory of the previous state.
Tower’s age-dependent extension links adaptation to aging through antagonistic pleiotropy: a trait is beneficial early in life but harmful later. A transition can be reversible while the consequences of time spent in the beneficial state persist. If females and males benefit from different transition frequencies, a shared genetic regulator leaves both sexes at a compromise value; independent regulation could bring each sex closer to its own optimum.
Two yeast studies test individual steps in this reasoning. In an experiment with an artificially controlled rate of state switching, fast switchers had an advantage when the environment changed rapidly, while slow switchers had an advantage when it changed infrequently. In data on environmental memory, the ability of mutants to reproduce under current conditions often depended on previous conditions; Tower’s reanalysis uses this as evidence that outcomes depend on the history of transitions.
The model sets out a testable sequence: identify which regulated transition is beneficial under particular conditions, determine the cost of initiating it and the effects that persist later, and establish whether the optimal frequencies differ between the sexes.