Our capacity to care about others may have very, very ancient origins, a new study suggests. It might have been deep-rooted in prehistoric animals that lived millions of years ago, before fish and mammals like us diverged on the tree of life, according to researchers who published their study Thursday in the journal Science. Scientists are usually reluctant to attribute humanlike feelings to animals. But it's generally accepted that many animals have moods, including fish. The new study shows that fish can detect fear in other fish, and then become afraid too " and that this ability is regulated by oxytocin, the same brain chemical that underlies the capacity for empathy in humans. The researchers demonstrated this by deleting genes linked to producing and absorbing oxytocin in the brains of zebrafish. Those fish were then essentially antisocial " they failed to detect or change their behavior when other fish were anxious. But when some of the altered fish received oxytocin injections, their ability to sense and mirror the feelings of other fish was restored " what scientists call "emotional contagion." "They respond to other individuals being frightened. In that regard, they behave just like us," said ... neuroscientist Ibukun Akinrinade, a co-author of the study. The study also showed that zebrafish will pay more attention to fish that have previously been stressed out " a behavior the researchers likened to consoling them. Previous research has shown that oxytocin plays a similar role in transmitting fear in mice.