Reading about yawning right now might actually make you yawn. Here's the strange science behind why

[Wardlow86]

Yawning likely arose alongside the very first jawed fish roughly 400 million years ago, according to evolutionary biologist Andrew Gallup, who has spent years studying the behavior. Every vertebrate species studied so far yawns spontaneously in some form, suggesting it serves a genuinely deep, ancient biological function rather than being a quirky human habit.

What that function actually is remains debated. One leading theory holds that yawning helps regulate brain temperature, working something like a cooling fan, drawing in cooler air and increasing blood flow to help the brain avoid overheating. Another older theory pointed to carbon dioxide buildup and oxygen exchange, though more recent research has leaned harder toward the thermoregulation explanation.

Contagious yawning is a separate and stranger phenomenon entirely, one only documented in highly social species, humans, chimpanzees, dogs, and even lions among them. Roughly 40 to 60 percent of people yawn after watching someone else do it, and researchers increasingly connect that response to empathy and social bonding rather than pure tiredness. A 2021 study on lions found that individuals who caught a yawn from another lion were eleven times more likely to then mirror that lion's subsequent movements, a striking hint that yawn contagion might help synchronize group behavior.

Not everyone catches yawns equally. Individuals scoring higher on measures of psychopathic traits tend to be less susceptible to contagious yawning, and the response typically doesn't appear in humans until around age four, right around when children develop theory of mind, the ability to understand that other people have their own separate thoughts and feelings.

Why is yawning contagious?www.livescience.com