Yawning is pretty weird, when you think about it – especially the part where we can catch them from others (even animals!). If you’re curious about why we do it at all, keep reading!
Science is 100% sure why some species yawn – baboons and guinea pigs yawn as part of a threat display, while penguins do it as part of a mating ritual, for example. When it comes to human beings, however, we’ve got a few theories but no hard facts.
One is that yawning controls brain temperature, while another posits that the brain chemicals controlling our appetite, mood, and emotions could cause yawning – some studies correlate the latter, but no definitive proof has been found.
A more popular theory is that humans yawn to keep ourselves alert, which makes sense when you realize how often you do it when bored or tired. Several studies have confirmed that yawning can increase our attentiveness similar to the jolt we get from caffeine.
This would have been particularly important for early humans, who would have needed to stay alert and on the lookout for predators, etc, on a daily basis.
As far as yawns being contagious, the idea that yawns keeps us alert might explain this, too. If a yawn spreads, it could make an entire group more alert instead of just one person, and since humans are social by nature, evolution prioritizes behaviors that helps us connect with each other.
Interestingly, people with psychological disorders that inhibit empathy, like autism and schizophrenia, are less likely to catch a yawn, which lends further credence to the idea that yawns, and catching them, are intertwined with our ability to connect and empathize with others.
Any way you slice it, yawning isn’t a bad thing – it keeps us alert, jolts our brain, keeps us comfortable, and allows us to feel connected to others in our species.