Deep in the jungles of Tanzania, a chimpanzee gave birth to a severely disabled female infant. The female was completely dependent, unable to walk on her own, and showing symptoms similar to Down syndrome—a death sentence for those unfortunate enough to be born in the the wild.

Instead of abandoning the needy child, the mother, along with her older daughter, spent two years caring for the female, until it was presumed to have died. What makes this story incredible is that this was the first time scientists have observed chimpanzees nursing the disabled for an extended time, according to a Japanese study published this week in the journal Primates.

Caring for creatures with disability may seem strange in the chaotic and unaccommodating environment of the animal kingdom—but University of New Mexico anthropologist Martin Nicholas Muller tells Upvoted that he isn’t surprised by these findings.

Chimpanzee mothers are highly invested in infants and will go to extraordinary lengths to care for them, he says. In Uganda, Muller once saw a chimpanzee carry her dead baby around for two weeks—unprepared to give up on it.

“The stench from the corpse was so bad that other chimpanzees would threaten her when she sat near them, but she would not let her baby go,” Muller describes.

You can see an example of a mother dealing with a dead infant in this video by the Chimfunshi Wildlife Orphanage Trust.

And chimpanzee mothers care for sick infants all the time. Muller is unsure how common it is to care for the disabled, specifically, since they rarely live long enough in the wild.

But he did observe a chimpanzee mother attentively care for a handicapped infant born with spina bifida, until it died a few days later.

This video by the Jane Goodall Institute shows us just how tight the bond is between a mother and her child.

This seemingly altruistic behavior is not limited to primates. In laboratory experiments, rats will pay a high cost to help another that is suffering, he says. And wild orcas has been shown to go to great lengths to care for their disabled or malformed young, according to a report in the Journal for Critical Animal studies.

Though it’s much rarer to find examples of unrelated adults helping each other in this way. If an adult chimpanzee is so sick that it’s unable to leave its nest, nobody will bring it food, explains Muller.

And it’s not unusual for male chimpanzees to kill—and sometimes eat—infants that are not their own, destroying the competition’s offspring so they have a higher chance of copulating with the female sooner.

And while females do not murder their own infants, they have ferociously killed the infants of rival females.

In 1976, famed scientist Jane Goodall wrote about “a barbarous murder” in Tanzania. A female chimp—aptly referred to as Passion—stole an infant chimpanzee from its mother’s arms. Passion bit its skull and “feasted on the bloody remains,” Muller described in his report published in Current Biology.

The mother and her daughter Pom went on rampage—murdering four other infants. It was suspected that they were attacking “new immigrants” to the region, to preserve their limited resources. But their behavior still remains a mystery.

“Chimpanzees can be fairly brutal, but no more so than humans. And like humans—they also have a gentle and playful side,” says Muller.

While chimpanzees are humans closest living relatives, we must not confuse their gentle side for empathy. Caring for their disabled does not provide evidence that they understand another individual’s emotional state—the definition of empathy.

“Although I don’t think this study showed anything about empathy, I do think there is strong evidence for it in chimpanzees,” he said.