[1][3] McBrearty's work on the Middle Stone Age (MSA) in Africa helped kickstart a paradigm shift in the understanding of modern human behavior.
[4] With colleague Alison S. Brooks, McBrearty published "The revolution that wasn't: a new interpretation of the origin of modern human behavior," one of the most-cited papers in the history of Paleolithic archaeology.
[5] This paper argued that behavioral modernity arose in Africa over a long period of time, and that it is visible very early in the MSA archaeological record.
[6][7][8] McBrearty collected the first fossil, a molar tooth, during her surveys at Kapthurin in the East African Rift Valley in 2004, and immediately suspected that it belonged to an ape.
Researchers did not expect to find the ancestors of chimpanzees in the drier savannahs of the Rift Valley, typically seen as the ecological niche of archaic humans, but McBrearty believes that there are more examples there because of the better preservation.