Did you think that humans are the only species capable of showing empathy? Think again!

Some fish also show it. That’s the finding of a recent study published in the journal Science.

Researchers from the Instituto Gulbenkian de Ciência (Portugal) conducted several types of experiments on a species of zebrafish to study the role that oxytocin production plays in their ability to feel empathy. More precisely, their ability to transmit the emotion of fear. A phenomenon that the authors of the work refer to using the term “emotional contagion,” that is to say “the most ancestral form of empathy,” they specify.

In their experiments, the researchers concluded that oxytocin is both necessary and sufficient for zebrafish to mimic the distressed behavior of one of their own species. For example, a test showed that when fish watched videos showing other fish in danger, they had the reflex to move closer to their fellow fish, as if to connect with them or aid in recovering from the stressful experience.

“The brain regions associated with emotional contagion in zebrafish are homologous to those involved in the same process in rodents (e.g., striatum, lateral septum),” the study authors explain, “our results support an evolutionary conserved role for oxytocin as a key regulator of basic empathic behaviors across vertebrates.”

In other words, the emotional contagion observed in these fish, as well as in other species, is similar to the ability of humans to understand and feel the emotions of others.

Although more research is needed to support this theory, it suggests that emotional contagion appeared several million years ago, and then evolved from species to species, until humans developed the capacity for what we now term “empathy.”