This funny tale stems from the extensive analysis conducted by geneticists to reconstruct the birds’ evolutionary epic: that mad conquest of the skies led by a handful of surviving dinosaurs.
This project, called 10,000 Genomes, started in 2015. The goal: to sequence and classify the genetic sequence of a representative of the 34 known bird orders, then a representative of the 240 families, then one of the 2250 genera, finally a representative of about 8000 different species. Enough to create a beautiful evolution tree!
In the coming days, the international team will submit their work for the 240 families for publication (the order situation has already been completed). And already they realize it: There is an intruder, an unclassifiable one, another one: the Hoatzin. “A hideously unruly species,” one of the researchers confided. The hoatzin, or “sassa” in Guyanese Creole, is a pheasant-sized bird that lazes in the foliage of the Amazon mangroves. And his behavior is already bizarre.
Unique among birds, chewing the cud like a cow: its breast has given way to a huge harvest in which leaves and buds are fermenting. Other Quirks: The baby bird instinctively knows how to swim, even underwater; it has a pair of dinosaur-like claws on each wing that enable it to climb trees; and he can move on all fours like a quadruped. But most mysterious is its genome: It’s the only bird that doesn’t have a cousin species alive. He’s lost in the tree: he’s the sole representative of his order, mowed just for him for want of something better.
For morphological reasons, for a long time it was related to chickens, then to cuckoos. Then, for genetic reasons, one approached the group of “terrestrial birds” (like the peacock), then the order of waders, small waders. But that has nothing to do with the new sequencing either: the blur remains.
Without a common ancestor with other birds, it is impossible to trace the origin of its branch. According to some, the hoatzin’s mystery may never be solved. It can therefore forever remain the most mysterious of all birds. A real alien…