Thread by @NAChristakis

While spontaneous yawning is common across all vertebrate classes, *contagious* yawning is less common and has been observed only in a few species of *social* animals.

But, sweetly, elephants yawn when we do. 1/

A 2018 review of functions of yawning: sciencedirect.com/science/articl…

A 1999 review of *evolution* of yawning: link.springer.com/article/10.100… 2/

Elephants were shown to yawn in 2017. frontiersin.org/articles/10.33… 3/

*Interspecific* contagious yawning in response to human yawning had been seen only in chimpanzees and dogs.

But new 2020 work shows elephants engage in both intraspecific contagious yawning and interspecific contagious yawning with *familiar* humans.

frontiersin.org/articles/10.33… 4/

The functions of yawning are not wholly clear. Yawning may prompt brain arousal and activation. But why is it contagious? Yawning by an arousing elephant, prompting contagious yawns from elephants already awake could facilitate a state of higher arousal throughout a herd. 5/

The social contagion of emotional states may function to synchronize coordinated action of all sorts within social animals, and yawning may function partly in this manner (for more, via @connected_book, see: amazon.com/Connected-Surp…). 6/

The *social contagion* of yawning reflects a host of adaptive responses independently evolved by elephants and humans (via convergent evolution), as discussed in #BLUEPRINTbook amazon.com/Blueprint-Evol…. 7/

But the remarkable existence of *inter-specific* contagion of yawning is something else.

As also discussed in #BLUEPRINTbook amazon.com/Blueprint-Evol…, it may be of a piece with many examples of elephants (empathetically) coming to the aid of humans in distress. 8/

Just like humans might come the aid of (often social) animals in distress (like cutting netting off a baby seal -- ) elephants can do the same for us. Makes you think, doesn't it? 9/