Field of Science

Evolution highlights XVI

Monkey and duiker DNA found in gorilla shit suggest that gorillas eat meat in the wild, too. Or that they eat ants that eat monkey and duiker. Or that monkeys and duikers nibble at the gorilla dung. Or that they peed on it. Or stepped in it. Or that someone who licked a monkey and a duiker spit in the poo. Make up your own stories...

Why is this about evolution? Consider this:
Plus, "most herbivores can digest meat quite well," said study co-author Michael Hofrieter, a geneticist also at the Max Planck Institute. "It just does not work the other way around."
One of the projects I am working on is about the evolution of specialists vs. generalists. Sometimes new specilaists evolve by mutating to have a non-zero affinity for a new resource (say, plants), and then specialize on the new resource by losing the affinity for the first resource (e.g. meat). Seems like gorilla are on the path to becoming plant specialists, but aren't quite there yet. They are still generalists, but with a low affinity for meat.

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Fossils of a proto-dinosaur, Asilisaurus, dated to 10 million years before the first dinosaurs show that they weren't carnivores and walked on two legs, as previously thought.
The individuals stood about 1.5 to 3 feet (0.5 to 1 meter) tall at the hips and were 3 to 10 feet (1 to 3 meters) long. They weighed about 22 to 66 pounds (10 to 30 kilograms), walked on four legs, and most likely ate plants or a combination of plants and meat.
I'll bet they ate both meat and plants (see above). Or, just maybe, some big bipedal carnivore urinated on Asilisaurus scat.

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Way, way before the Cambrian explosion (which took 80 million years!), at 716.5 million years ago (now that's accuracy for ya!), most of the globe was covered in ice and snow, according to Harvard geologists (if it's Harvard, you know it's true):
The rocks Macdonald and his colleagues analyzed in Canada's Yukon Territory showed glacial deposits and other signs of glaciation, such as striated clasts, ice rafted debris, and deformation of soft sediments. The scientists were able to determine, based on the magnetism and composition of these rocks, that 716.5 million years ago they were located at sea level in the tropics, at about 10 degrees latitude.
Imagine how much such a five million year ice-age must have changed evolutionary trajectories. Perhaps this was yet another event crucial in paving the way for animals, tetrapods, etc., all the way up to the end-product: birds.

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