![]() Indeed, that’s why its genome is so weird. “In either case, it was well-adapted for its preferred lifestyle.” But “the passenger pigeon’s genome is that of both a low-diversity species and a high-diversity one,” says Ben Novak, who worked on the study. It’s commonly assumed that animals with massive populations should be genetically diverse. Same goes for the ends of the passenger pigeon’s chromosomes: That’s why they’re more diverse than the middle. But in your wardrobe, the hats, scarves, socks, and shoes are still free and loose, allowing you to consider each item individually and choose the best ones for your ensemble. Recombination is low, so genes stick together in large blocks, making it hard to select for one without getting all the hangers-on. That’s what happens in the middle of the pigeon’s chromosomes. If you want to keep a particular shirt, you’re forced to keep everything else that goes with it. Unfortunately, you find that some miscreant has stitched all the shirts, skirts, and pants together. Imagine that you’re going through your wardrobe trying to chuck out any clothes you hate, while keeping only the ones you love. But in birds, recombination happens more often at the ends of chromosomes than in the middle. This process, known as recombination, breaks up blocks of genes, allowing natural selection to weed out the worst mutations and keep only the best ones. When animals reproduce, their chromosomes mix and mingle, shuffling their genes into new groups. This pattern-and the evolutionary forces that produced it-have important implications for understanding both why the passenger pigeon died out, and whether it'll be possible to bring it back. Indeed, Shapiro had never seen anything like this before. The band-tailed pigeon doesn’t share the same pattern its genome has roughly the same level of diversity throughout. DNA is packaged in chromosomes, and the team found that the genetic diversity at the ends of these chromosomes was exceptionally high, while the diversity in the middle was exceptionally low. That made sense, given how many of them there were.īut averages are deceptive. On average, the passenger pigeon’s genome looked to be extremely diverse-two to three times more so than that of any other bird that had been sequenced thus far. Using these samples, they sequenced the full genomes of four individuals, and compared them to the genome of the band-tailed pigeon-a close relative that still exists but lives in considerably smaller flocks.Īt first, nothing jumped out. But Shapiro and her colleagues Gemma Murray and André Soares have found some new twists to the old answers by collecting bits of skin from around 200 passenger pigeons, whose century-old, taxidermied bodies sit in museums around the world. These questions have been debated for decades. “Why didn’t tiny populations survive somewhere in refugia? I mean, we are pretty good at murdering things, but how did we kill every one of them?” “It’s always astounded me how something could have that large a population and entirely disappear,” says Beth Shapiro from the University of California, Santa Cruz. In a matter of decades, the continent’s most common bird has been completely wiped out, down to the last individual. They poisoned them, netted them, gassed them, hit them with sticks. Simon Pokagon, a Potawatomi author and leader, described them as “the grandest waterfall of America” and their sound as that of “distant thunder” or “an army of horses laden with sleigh bells.”Īnd then, people started shooting them. ![]() At their peak, there were a few billion of them, traversing the continent in gargantuan, nomadic flocks that would blacken the sky for hours as they passed overhead. Passenger pigeons were once the most abundant bird in North America, and quite possibly the world. This is an animal that existed in gestalt. But in many ways, the species was already gone, for a solitary passenger pigeon is almost not a passenger pigeon at all. With her demise, her entire species slid into extinction. On September 1, 1914, an old, trembling passenger pigeon named Martha died at Cincinnati Zoo.
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