200 Years. 200 Stories. Story 120: “This Looks Like a Primate ”

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Lithograph showing fossil mammals
1873 Lithograph showing several fossil mammals. The jaw of Notharctus is located second from the bottom in the lower left.

This Looks Like a Primate

In 1870, Joseph Leidy gave the name of Notharctus tenebrosus to a small fossil jaw he received from the Bridger Basin of the Wyoming Territory. Three years later, he provided a detailed description of it and 137 other fossil species in the first volume of a report for the Hayden Geologic Survey of the Western United States. Like most of his fossil descriptions, it was a detailed and dense account that would be useful to his fellow scientists but would be conspicuously uninteresting to most readers.

Remarkably, Leidy follows this description with the observation: “The resemblance is so close that but little change would be necessary to evolve from the jaw and teeth of Notharctus to that of a modern monkey.” He continues with the observation that additional—but relatively minor—evolutionary modifications would result in a jaw that resembled those of modern apes and humans.

Leidy never formally identified Notharctus as a primate (a group that includes lemurs, monkeys, apes, and humans), and he largely abandoned paleontology shortly after these comments were published. In any case, it’s clear that Leidy was an evolutionist. An occasional target of creationist attacks during his long career—including one that seriously threatened his livelihood, Leidy may have buried this discussion within the dense text in the hope that only the receptive reader would find it.

Read more about Notharctus on ansp.org.

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