Humans and monkeys may have evolved their keen ability to detect snakes due to a fear response triggered by the reptiles’ scales, rather than their elongated bodies, according to research from Nagoya University.
The findings, which could reshape the understanding of visual system evolution in primates, were published in the British scientific journal Scientific Reports.
Prof. Nobuyuki Kawai, cognitive scientist at Nagoya University’s graduate school who heads the research, explained that while humans and monkeys have long been believed to have an innate fear of snakes, the specific features that elicit this fear remained unclear.
To investigate, Kawai’s team conducted experiments using three Japanese macaques born in captivity and unfamiliar with snakes or newts. The monkeys were trained to identify an odd animal out of nine images displayed on a touchscreen, and the time it took them to do so was measured and compared.
As previous theories suggested, the monkeys were faster in identifying a snake among newts than in finding a newt among snakes, with one monkey detecting a snake an average of 0.84 of a second quicker than locating a newt.
The researchers then conducted the experiments using processed images of newts overlaid with snake scales. When shown these modified images, two of the monkeys took roughly the same amount of time to differentiate a scaled newt from snakes as they did to find a snake among such newts.
Interestingly, the third monkey identified a scaled newt among snakes faster than a snake among scaled newts.
The study concluded that primates might be particularly sensitive to the distinctive feature of snake scales.
“Snake-scale patterns could potentially be effective in preventing crop damage caused by wild monkeys,” Kawai suggested, highlighting potential applications for the research.
Translated by The Japan Times