The Last Thing These Chimpanzees Saw Before Their Own Group Did the Unthinkable

In a forest in Uganda, chimpanzees are hunting down their own family. The ones doing the killing used to share their trees and their food with the ones they kill. For decades, this was one group. Then it broke in two, and one half went after the other. It hasn't stopped. One evening, they come for a big, easygoing male called Basie. Three of them close in around his tree, He drops to the ground, and before he can get up, and the only way left is down. ten of them are on top of him, biting. A female tries to shield him. They chase her off fast. When they finally leave, Basie is still alive, and he's not alone for long. He wasn't the first. The first to die was Errol, a young male from the central side, about 16 years old. Five males from the western side caught him and killed him. They'd been feeding at a fig tree near the middle of Ngogo, their forest. Nobody patrolled the middle. It was where everybody ate. Were the chimps who killed him ones he'd eaten beside his whole life? The day Errol died, the killing started right in the center of the place they'd all called home. How does a tree everybody shared turn into the place you get torn apart? It broke on one ordinary day in June, four years before Basie died. A big group of the western chimps was traveling toward the center, the way they'd always done. Then, all at once, every one of them went quiet. Some of them pulled their lips back tight over their teeth. Others reached out and touched each other for reassurance. They were acting like strangers were coming. But the calls in the trees weren't strangers. They came from the central chimps, their own group. Normally, when the two halves met up again, it was a loud, happy mess, with hands held and backs patted. The western chimps turned and ran, the central chimps went after them, and it turned into chaos, screaming and chasing through the trees. Even the man who's followed these chimps for decades, and who's rarely surprised by anything they do, didn't know what was going on. Nothing like it had ever been seen in that forest. One of the chimps in the group the west ran from that day was Jackson, the new alpha who'd just thrown out the old one. The clock on him had already started. It just took years to run down. Whatever set it off, nobody saw it happen. The two halves of this family had just been spending less and less of their days together, until the day they met and acted like strangers. Every family has cousins who stop turning up. Every office has two lunch tables that don't mix. At Ngogo, that's how it started. Three years later, the first chimp was dead. The side that ran that day was the west, and it was the west that came through the trees for Basie. For a while, it looked like the two halves would just stay out of each other's way. That didn't last. The center of their home had become a border, and on a border, chimps kill. The chimps who could have pulled the two sides back together were already dying. The year before it broke, five old males and one adult female died of what looked like a lung sickness. Were those six the ones still grooming chimps on both sides? Still holding the two halves together? If they were, the split had started before anybody saw it. Two years after the day it broke, they weren't one group anymore. Each side had its own land, and each side patrolled its own edge. That was the year a sickness went through Ngogo. Coughing, sneezing, runny noses, chimps going limp and losing weight. 25 of them were dead inside 40 days. That's about one chimp in every eight. Among the dead were the last males who still had friends on both sides. It was a cold virus. The kind that goes around every school and office every winter. A human one. Since then, every researcher who wants to walk into that forest has to sit out a week in quarantine first. Did the last chimps holding this family together die of something that came in on us? Back on the forest floor, Basie is bleeding and he can barely move. That's when BF comes. BF is 53, which is ancient for a For more than 10 years, he and Basie have been something close to friends. He goes to Basie and helps him walk. Slowly, one step at a time, the whole way back to the heart of the land their side still holds. BF keeps to Basie's pace, through a forest where the west could come back for both of them. By the time they get there, it's dark. Basie has one night, and at the end of it, the sun is going to come up on the two of them. Basie was the second one killed. Before him, both sides sent patrols out along the edges. After him, the central and eastern chimps, the side with more males, stopped patrolling west at all. To the people watching them, it looks like they've given up. All of the killing in this war has come from the west. With nobody defending the border, what's left to stop it moving? The west keeps coming. Once, while a researcher was describing this war on camera, word came through on the team's group chat that the Westerners were traveling east. He hoped out loud that they wouldn't kill anyone. Two years after Basie, the West changed what it was hunting. Within a single year, Western chimps were seen stealing 14 babies from the central side. They were ripped off their mother's chests and battered to death. The line that started in the middle of the forest went through Basie's trees, and then it went into the arms of the mothers. When the West catches a grown male, five or ten of them pile on, hold him down, bite him, punch him, kick him, and drag him. 24 attacks in, the count is at least seven grown males and 17 babies. Fourteen more of their males are missing. Ten chimps can take one apart. So what happens to 14 that nobody sees go? Since that count was closed, there have been at least two more attacks on Central Males. Somebody is still out there in those trees, writing down every one of these attacks. The next time that list gets longer, I'll bring it here. Subscribe now, and you'll know how many are left. While the Central Side was losing its babies, the West was growing. It started this war as the Smaller Side, with 76 chimps. It's up to 108 now, and the Central Side keeps shrinking. Jackson was one of the ones who didn't make it. The alpha who was standing in the central group on the day the west ran, the one chimp empire followed, died of the wounds he took fighting the west. Without him, the central side couldn't settle who led it. Even while it was being hunted, its males were fighting each other for the top spot. For every chimp an ordinary group loses to its neighbors, the central side is losing more than 30. Every one of them killed by chimps they used to sleep beside. This isn't the first time this family learned that killing pays. Back when they were still one group, they went to war with their neighbors, killed neighboring chimps in 18 separate attacks, and moved into the land where most of those killings had happened. Over the next three years, the number of babies born went from 15 to 37. Killing their neighbors paid them in babies. And those babies helped make this the biggest chimp group anyone had ever followed, a size that's one of the things that split it. Now, the killing is aimed at their own. What does the West do with the middle of that forest once there's nobody left on the central side to feed in it? The only other time anyone watched a chimp group split and go to war with itself, it started when six males caught a young male alone in a tree and beat him until he stopped moving. An old male who'd stayed friendly with the attackers had his leg twisted like they wanted it off. An old female was beaten while one of her own daughters, who'd gone over to the attackers, watched. The last male on that side got through more than a year on his own before they found him. They dragged him down a slope, and a day later, he was gone for good. By the end, every male on that side was dead or gone. Then the winners found out what they'd lost, and that's the part the West hasn't reached yet. The dead had been standing between them and the group to the south. With them gone, the winners got squeezed until their land shrank to a scrap, and the male who'd held down that first victim was killed by the neighbors. That war took four years to finish off the losing side. At Ngogo, the killing has been going on for more than six, and it's still going. Back at Ngogo, the night goes on. Basie lies down, bleeding and weak. BF stays with him through the dark, gesturing over and over like he's in distress. How many of the chimps who came for Basie that evening had groomed him? Had he ever gone out with some of those same males against somebody else's group? By morning, BF is still there. Basie is barely alive. BF reaches out and holds his hand open toward him, like he wants Basie to get up and follow him. That's the last thing Basie had in front of him. All the faces that came through the leaves for him the evening before belonged to chimps he'd lived beside his whole life. So did this one. BF was the one who stayed. Basie died that day. A split like this happens in a chimp group about once every 500 years. This time, people were standing in the leaves, writing it down. What's happened in all the forests where nobody was standing there to watch? The central side is being wiped out, and the man who's followed this family for decades calls it an extinction event. At night, it still builds its nests where a patrol can reach them. BF was 53 on the night he walked Basie home. How many more nights does an old male on the losing side get? The West has taken Errol, Basie, Jackson, and the Babies. The one thing it couldn't take from Basie's last night was BF. If the West finishes what it started, the last thing the rest of the Central Side ever sees will be the same line of faces Basie saw coming through the leaves.