Evolutionary Biology of Aging

by

Grant A. Rutledge, Michael R. Rose

• LAST REVIEWED: 09 May 2023
• LAST MODIFIED: 26 April 2018
• DOI: 10.1093/obo/9780199941728-0105

Introduction

Evolutionary biology offers a coherent and experimentally supported theory for biological aging. Here we will introduce the literature on the evolutionary biology of aging, starting with formal theory. Over the last forty years this field has developed important empirical foundations. The longest standing data pertaining to the evolutionary biology of aging naturally are its comparative biology. We will touch on the quantitative genetics of aging and its manipulation using experimental evolution. Lastly, we will consider research on the cessation of aging, a recently uncovered phenomenon of great interest from an evolutionary standpoint.

Early Evolutionary Theories of Aging

August Weismann was the first to publish an explanation of senescence in terms of evolution by natural selection. In his lecture titled “The Duration of Life,” delivered in 1881, Weismann proposed that longevity was programmed according to “the need of the species” (Weismann 1891, p. 9). He rejected the idea that an organism’s longevity was determined merely by its physiological “construction,” arguing instead that evolution could shape longevity according to the dictates of natural selection, as he understood them. The need for death was an important theme in Weismann’s “The duration of Life.” He explains that if an individual was not killed by accident, it would experience injuries over time. A limited ability to heal such injuries would result in older individuals having lower Darwinian fitness than younger individuals. Older individuals would therefore take limited resources that could be better allocated to younger individuals, thus creating a selective advantage (at the level of the population or group) for dying at old ages. Weismann proposed limits to somatic cell replication as a mechanism for this inability to heal. In his own language (as translated), “when one or more individuals have provided a sufficient number of successors they themselves, as consumers of nourishment in a constantly increasing degree, are an injury to those successors . . . natural selection therefore will weed them out.” In his essays “Life and Death” and “On Heredity,” Weismann suggested that once a selective advantage for death had been established, there would be no barrier to selection for any advantageous traits that might trade-off against immortality. The forgoing of immortality might make additional resources available to reproductive cells. This evolutionary loss of immortality he attributed to “panmixia.” The central idea of Weismann’s theory is that characters useless to an organism escape the action of natural selection and therefore disappear (Kirkwood and Cremer 1982). Weismann’s panmixia theory seems to be an anticipation of modern thinking about the evolution of aging.

• Kirkwood, T. B. L., and T. Cremer. 1982. Cytogerontology since 1881: A reappraisal of August Weismann and a review of modern progress. Human Genetics 60:101–121.

  DOI: 10.1007/BF00569695

  Kirkwood and Cremer review the work of August Weismann and his emphasis on the preeminent role that selection plays in the evolution of senescence. They also assess the research in the field of aging from an evolutionary and cellular standpoint. They believed that Weismann’s theory and thoughts were, “more extensive in their scope and more pertinent to current research than is generally recognized” (p. 101).

• Weismann, A. 1891. Essays upon heredity and kindred biological problems. Vol. 1. 2d ed. Oxford: Clarendon.

  This volume published in 1891 contains three key essays delivered in the early 1880s. The essay “The Duration of Life” was the first to offer a theory for the evolution of senescence based on Weisman’s interpretation of how natural selection might shape aging. Weismann proposed senescence evolved for the “good of the species”; older individuals die off to allow adequate nourishment for younger individuals. But his other essays on aging focus more on selection at the level of individuals.