The theory of nighttime vigilance is not new, reports Healthline.

“Forty to 72 percent of the variability we see in chronotyping” — each individual’s internal clock, which determines sleep behavior based on circadian rhythms — “is explained by genetics,” Samson told Healthline. “The rest is variable by environment, culture, social factors, and now technological factors.”

Most sleep research is conducted in a lab setting, noted Samson, “not in an evolutionarily relevant context.”