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How did Stephen Jay Gould argue that selection can occur at the species level?

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Marble bust of Aristotle with a beard and draped robe, showing detailed facial features and wavy hair, set against a dark background. — Philosophy of biology Detail of a Roman copy (2nd century bce) of a Greek alabaster portrait bust of Aristotle, c. 325 bce; in the collection of the Roman National Museum.

The American paleontologist Stephen Jay Gould argued that species selection is a significant factor in macroevolution—the study of evolutionary changes over millions of years.1

Gould’s argument was not merely that individual members of a successful species possess advantageous traits that others lack. Instead, he proposed that species can possess emergent features—characteristics that belong to the species as a whole rather than to its individual members—and that these features can be the direct targets of selection.1

A primary example Gould cited is reproductive isolation. He suggested that such features influence the likelihood of a species to undergo speciation or extinction. For instance, if members of one species are more prone to wandering, that species might break up and speciate more frequently than another, leading to greater overall variation in its descendants. While critics argued that such outcomes might be accidental by-products rather than adaptations, Gould maintained that species selection remains a critical, distinct level of evolutionary process that operates beyond the individual organism.12