Pansy was probably in her 50s when she died, which is pretty good for a chimpanzee. She passed in a way most of us would envy — peacefully, with her adult daughter, Rosie, and her best friend, Blossom, by her side. Thirty years earlier, Pansy and Blossom arrived together at the Blair Drummond Safari and Adventure Park near Stirling, Scotland. They raised their children together. Now, as Pansy struggled to breathe, Blossom held her hand and stroked it.

When the scientists at the park realized Pansy’s death was imminent, they turned on video cameras, capturing intimate moments during her last hours as Blossom, Rosie and Blossom’s son, Chippy, groomed her and comforted her as she got weaker. After she passed, the chimps examined the body, inspecting Pansy’s mouth, pulling her arm and leaning their faces close to hers. Blossom sat by Pansy’s body through the night. And when she finally moved away to sleep in a different part of the enclosure, she did so fitfully, waking and repositioning herself dozens more times than was normal. For five days after Pansy’s death, none of the other chimps would sleep on the platform where she died.

This account was published in 2010 in the journal Current Biology, but it’s not the only time scientists have watched chimpanzees, bonobos and other primates deal with death in ways that look strikingly like our own informal rituals of mourning: watching over the dying, cleaning and protecting bodies and displaying outward signs of anxiety. Chimps have been seen to make loud distress calls when a comrade dies. They investigate bodies as if looking for signs of life. There are many cases of mothers refusing to abandon dead infants, carrying and grooming them for days or even weeks. Still, it’s rare to capture primate deaths, especially those of chimpanzees and bonobos, in detail. It happens just often enough that many scientists are starting to think there’s something interesting, maybe protohuman, going on.

But this sort of speculation is laden with epistemological issues: are the scientists guilty of anthropomorphizing their subjects? Are these just isolated events? Are they more likely in captivity? Stories like Pansy’s are mere anecdotes in a world that demands testable hypotheses, and they color the fringes of a continuing scientific debate: Can we find the basis for aspects of our culture in the behavior of other primates?