Raymond Pearl

Raymond Pearl (3 June 1879 – 17 November 1940) was an American biologist, regarded as one of the founders of biogerontology. He spent most of his career at Johns Hopkins University in Baltimore.

Pearl was a prolific writer of academic books, papers and articles, as well as a committed populariser and communicator of science. At his death, 841 publications were listed against his name.

Background
Born of upper-middle class parents in New England, Pearl excelled at school and went on to Dartmouth College where he gained his B.A. in 1899, and the University of Michigan where he gained his PhD in zoology in 1902. In 1906 he spent a year studying under Karl Pearson at University College, London. During this year he discovered biometry, which seemed to offer a solution to the problems he was concerned with in biology, zoology and eugenics. On his return to the US he continued his interests, but was converted from biometry to Mendelian genetics.

Science
Pearl is regarded as one of founders of biogerontology. In 1908 Max Rubner observed that mammals of different size and longevity had equal mass specific metabolic output. Partly based on the observation that the longevity of fruit flies varies inversely with ambient temperature, Pearl (like Rubner) also asserted that maximum life span is inversely proportional to basal metabolic rate. Pearl accepted Alexis Carrel's erroneous ideas that normal somatic cells don't age, and that aging must therefore be due to dysfunction at the body level. Pearl speculated that lifespan was limited by vital cell components that were depleted or damaged more rapidly in animals with faster metabolisms. Denham Harman's free radical theory of aging later provided a plausible causal mechanism for Pearl's hypothesis.

The Rate of Living Hypothesis enjoyed prominence as one of the foremost theories of aging for nearly 50 years. The Rate of Living Hypothesis is undermined by the observation that a rat and a bat have similar metabolic rate, but a bat lives several times longer. More recently, further doubts have been raised on the Rate of Living Hypothesis by the demonstration that, when modern statistical methods for correcting for the effects of body size and phylogeny are employed, metabolic rate does not correlate with longevity in mammals or birds. (For a critique of the Rate of Living Hypothesis see Living fast, dying when?. )

In 1926 Pearl founded The Quarterly Review of Biology. He also served on the board of trustees for Science Service, now known as Society for Science & the Public, from 1929-1935.