Evolvable soma theory of ageing: observations from the natural world.

Abstract

Ageing has traditionally been interpreted through declining selection gradients with age. The Evolvable Soma Theory of Ageing (ESTA) provides a complementary perspective by proposing that age-associated somatic changes reflect the late extension of the developmental program, which is shaped by evolution. These late-acting changes are epigenetic in nature, encoded in the genome, subject to germline-mediated modification, and may be viewed as developmentally regulated variants that have not yet been refined by selection. Here, we explore whether patterns observed in the natural world are consistent with key expectations derived from this framework. One such expectation is that species experiencing lower rates of evolutionary change may exhibit slower age-associated decline. In line with this idea, we examine long-lived species occupying ecological niches characterised by reduced competition and environmental turnover, as well as taxa often described as exhibiting high evolutionary stasis, and note that several display extended lifespans compared to related groups. Secondly, we examine evo-devo dynamics concerning the relationship between development and evolutionary history, and discuss their compatibility with the conceptual structure of ESTA. A third expectation is that stronger evolutionary pressure may influence life-history timing, including shifts in the age of sexual maturation; this possibility is explored through comparisons between bonobos and chimpanzees and through broader sex-specific patterns reported in mammals. Taken together, these observations do not constitute definitive tests but provide preliminary, qualitative support for the idea that evolutionary dynamics and ageing may be more closely intertwined than traditionally assumed, and they highlight directions for future investigation.