Connor Bernard, Aldo Compagnoni and Roberto Salguero‐Gómez
Senescence describes an organism’s physiological degradation with age, resulting in a higher risk of death and reduced reproductive performance over time. In recent years, many species across the Tree of Life have been identified that fail to conform to this pattern of senescing and its underlying classical theories. Certain species become more reproductive and less susceptible to death with age. Evolutionary biologists are now grappling with the question of how to account for these cases of neutral or negative senescence that run opposite to classical predictions and which contradict the foundation of classical senescence. In 1990, Caleb Finch posited a possible mechanism for reducing the strength of senescence based on the architecture of certain plants and animals – those comprised of repeat compartments, called modules. Finch’s hypothesis holds that, just as a ship can stay afloat with a breached hull if the damage can be isolated to select compartments, plants and animals with modular anatomies would be more resilient to death if their anatomies prevent local injuries from spreading and becoming fatal to the organism. Advances in data now allow us to test Finch’s hypothesis across a wide range of plants and animals, and ask: Do more modular anatomies correspond with a reduced pattern of senescence? Our review of 138 plants and 151 animal species suggests that Finch’s predictions hold in plants, but possibly not animals. Significantly lower rates of senescence are found in more modular plants, providing early evidence for a widespread phenomenon that may lie at the heart of a crucial evolutionary puzzle.