It is estimated that some 99 percent of the about 4 billion species that have evolved on Earth have disappeared. According to paleobiologist Anthony Barnosky, extinction of species caused by humans is now happening at such an accelerated rate that, in just about three centuries, 75 percent of all mammal species will be gone.
The fossil record gives us just the barest sense of the rich, rich diversity of species that once thrived on Earth. Some recent discoveries:
1. The oldest known domestic dog
While humans began to domesticate dogs over 10,000 years ago (before the beginning of agriculture), we don’t know exactly when modern dogs became a species distinct from wolves. A 33,000 year old fossil tooth from southern Siberia has yielded DNA confirming that the tooth belonged to one of the oldest known domestic dogs.
Analysis of the DNA found that the tooth belonged to an animal who is more closely related to prehistoric canids and to domestic dogs on the American continents than to wolves. Some previous studies have suggested that modern dogs and wolves became distinct species 100,000 years ago — this new study by Russian researchers suggests the two species emerged much later.
2. A new hippo-like mammal
While Central America’s subtropical regions are some of the most diverse, lush vegetation has made paleontological excavations difficult. Recent excavations of the Panama Canal that began in 2009 have unearthed the fossils of a hippo-like mammal previously unknown to science.
According to University of Florida archaeologists, the now-extinct mammal lived about 20 million years ago and is an anthracothere, a mammal with even-toed hooves who is believed to be related to today’s hippos and who has a “hypothetical relationship with whales.” About the size of a cow, the mammal was, like the hippo, semi-aquatic.
3. Not one but two new ancient species of crocodilians
The University of Florida archaeologists also found the partial skulls of two new species of caimans in rocks that are 19.83 to 19.12 million years old. One of the species, Culebrasuchus mesoamericanus, is thought to represent an evolutionary transition between the caimans of South America and the alligators of North America.
The isthmus of Panama was formed 2.6 million ago, creating a land-bridge that has been thought to have made it possible for armadillos and giant sloths to move up to North America while modern horses, rabbits, pigs, cats, dogs and elephants moved down. Along with the new mammal fossil, those of the crocodilians provide a new understanding of species distribution at a time before the isthmus existed, when oceanic waters separated the North and South American continents.
4. Camels in Canada
Scientists have found 30 fossil fragments from a leg bone of an ancient camel in a site in the Canadian arctic. Camel fossils have previously been found in Canada; the new find is 1,200 kilometers farther north than earlier discoveries.
The fragments (part of a large tibia) were first thought to possibly be wood. Scientists digitized images of the bone fragments and also used a new procedure, collagen fingerprinting, to analyze them. Collagen is the main protein in bone; samples of it were extracted from the fossils and found to match those of modern camels (dromedaries, who have one hump). They also matched samples from a fossil of a giant camel previously found in the Yukon.
Camels have been called the ships of the desert, so it may come as a surprise to learn that their ancestors originated from North America about 45 million years ago. It’s not that northern Canada was once a desert, but that camels may have originally lived in a far colder climate. As researchers note, modern camels have adaptations for living in a polar environment, such as large eyes, wide flat feet and their iconic humps.
The remains of giant tortoises and alligators have also been found in the arctic, fascinating clues to what life on earth was like once upon a very long time ago.
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