The Evolutionary Accident Distinctive to Homo Sapiens

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In 1979, famend evolutionary biologists Stephen J. Gould and Richard Lewontin published “The Spandrels of San Marco and the Panglossian Paradigm,” a comparatively quick treatise pushing again on what they noticed as a disconcerting pattern of their discipline. 

Evolutionary biologists, the 2 wrote, had develop into enamored with atomizing organisms into discrete traits and telling “just-so stories” about how these particular person elements had develop into optimized by pure choice to their superb kind. 

To illustrate the fallacy of this mode of considering (what they referred to as “the adaptationist’s programme”), they used the instance of “spandrels” in Venice’s St. Mark’s Cathedral. A “spandrel” is the curved triangular house between two arches at proper angles to one another, and in St. Mark’s they’re embellished with detailed mosaics. 

It could be fallacious to say the spandrels have been created for the aim of displaying mosaics, Gould and Lewontin defined. Instead, they have been architectural byproducts of arch building, embellished after the actual fact. And simply as spandrels are byproducts of the constraints of architectural house, many organic traits are byproducts of the constraints of bodily and developmental processes, Gould and Lewontin argued.

Since publication of their paper, “spandrel” has develop into shorthand amongst evolutionary biologists for an incidental trait, or results of a byproduct of evolution. Now, a brand new research published in PLOS One is investigating the potential spandrelhood of a human trait: the chin.

Read extra: “What Made Early Humans Smart”

Absent from different primates—and even Denisovans and Neanderthals—the bony, protruding chin is a uniquely human attribute and infrequently used to establish members of our species within the fossil report. As such, it’s tempting to take pleasure in one other uniquely human trait (storytelling) and provide you with a motive it was honed by pure choice. Among others, supporting the decrease jaw to facilitate chewing or appearing as a secondary sexual attribute to promote maturity to mates, are two such tales. 

To examine theories of the evolution of the chin, researchers from the University of Buffalo examined gene sequences concerned within the improvement of the pinnacle and jaw for proof of evolution. Specifically, the workforce checked out whether or not sequences concerned in producing the chin itself have been topic to direct choice, whether or not they arose neutrally because of genetic drift, or whether or not they have been merely a byproduct of evolution appearing upon different traits (a spandrel). They discovered that the proof pointed towards the chin being a spandrel.

“The chin evolved largely by accident and not through direct selection, but as an evolutionary by-product resulting from direct selection on other parts of the skull,” research creator Noreen von Cramon-Taubadel mentioned in an announcement.

The traits pure choice was most certainly appearing on included lowered anterior dental measurement and different cranial modifications associated to the evolution of bipedalism, the authors clarified.

“While we do find some evidence of direct selection on parts of the human skull, we find that traits specific to the chin region better fit the spandrel model,” von Cramon-Taubadel defined. “The changes since our last common ancestor with chimpanzee are not because of natural selection on the chin itself but on selection of other parts of the jaw and skull.”

It’s an vital reminder that traits needs to be thought of inside their context, and that not all variations between species are a results of an omnipotent power of pure choice. 

“Generating empirical evidence against that line of reasoning is an important goal of this study and biological anthropology in general,” von Cramon-Taubadel mentioned. “The findings underscore the importance of assessing the evolution of physical characteristics with trait integration in mind.”

Something to stroke your chin and take into consideration.

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Lead picture: cybermagician / Shutterstock

• Jake Currie

  Posted on February 17, 2026

  Jake Currie is a author primarily based in Brooklyn, NY.