About 56 million years ago, on a Earth so hot that palm trees adorned the Arctic Circle, a primate the size of a mouse, called Teilhardina first wrapped his fingers around a branch.
The oldest known ancestor of modern primates, TeilhardinaRelatives of the latter will finally give birth to the apes, apes and humans of today. But one of the persistent mysteries about our distant cousin is at the origin.
Teilhardina (ty-hahr-DEE & # 39; -nuh) quickly spread to the forests of Asia, Europe & North America, a range unmatched by any other primates, to Exception of the man. But where did his journey begin?
New research shows that Teilhardina brandti, a species found in Wyoming, is as old or older than its Asian and European parents, going against the dominant assumption that Teilhardina first appeared in China.
TeilhardinaThe origins of, however, remain an enigma.
"The scientific conclusion is:" We simply do not know, "said Paul Morse, lead author of the study and recently graduated doctor from the University of Florida." While the fossils we found could reversing past assumptions of Teilhardina have come and where they have migrated, they certainly do not offer a clearer scenario. "
What is clear, says Morse, is that T. brandti had a wide variety of characteristics, some of which are as primitive as those found in Teilhardina asiatica, its Asian cousin, previously considered the oldest species of its kind.
To make this determination, Morse studied 163 teeth and jaws in the most complete analysis of the T. brandti nowadays.
Teeth contain a wealth of information and often keep better than bones, thanks to their resistant enamel. They can reveal clues about an animal's evolutionary past, its size, diet, and age as an individual and at a geological time.
According to Jonathan Bloch, co-author of the study and curator of vertebrate paleontology at the Florida Museum of Natural History, primate teeth have particularly distinct structures and immediately recognizable by a trained eye.
"Identifying the differences between the teeth of primates is not so different from a biker who recognizes that a Harley is different from a scooter or a criticism of a dog. art and who evaluates whether an image was created by Picasso or Banksy, "he said. "In detail, they are very different from each other in a specific and predictable way."
While Teilhardina bones are very rare in the fossil record, his teeth are more numerous – if you know how to find them. The team of paleontologists from Bloch, including Morse, spent years painting the surface of the Bighorn Basin, Wyoming, and then taking 50-pound sacks of earth into a river to filter them. The remaining bone fragments and teeth – which may be smaller than a flea – are examined under a microscope at the museum.
This careful research has built the dental record of T. brandti from a single molar – used for the first time to describe the species in 1993 – to hundreds of teeth, providing a general overview of the variation in the primate population level.
Yet, Morse and Bloch were not prepared for the particular variation presented by UF specimen 333700, a piece of jagged jaw with T. brandti the teeth.
"Jon and I started arguing about the cells" and their flaws, Morse said, now a postdoctoral fellow at Duke University. "At the end of the day, we realized that this specimen completely reversed the definition of T. asiatica and part of the reason why he is the oldest Teilhardina species."
Studies based on a small number of teeth simply missed the diversity of TeilhardinaThe physical characteristics of, says Morse.
"There is probably a huge amount of variation in the fossil record, but it is extremely difficult to capture and measure when the sample is small," he said. "That's one of the reasons why additional fossil collection is so important."
The analysis also reworked the Teilhardina genealogical tree, reducing from nine to six the number of species described and reclassifying two species into members of a new genus, Bownonomys, named in honor of the prominent vertebrate palaeontologist Thomas Bown.
But the precise age of Teilhardina species are still unidentifiable and can remain so.
Teilhardina appeared at the geological equivalent of a flash in the pan, a brief period of 200 000 years called the Paleocene-Eocene Thermal Maximum, or PETM. This era was characterized by a massive injection of carbon into the earth 's atmosphere, which caused a surge in global temperatures. Sea levels rose 220 feet, ecosystems were revised, and the waters of the North Pole warmed to 74 degrees.
Scientists can use the distinct carbon signature of the PETM to locate this period in the rock disk. Carbon isotopes in teeth can also be used to identify fossil animals of this time.
But among Teilhardina Fossil sites around the world, only Wyoming has uninterrupted rock layers, carefully delineated, which allow paleontologists to become familiar with more precise dates.
"The humblest statement would be to say that these species are essentially of equivalent age," said Bloch. "Determining what happened earlier in the PETM probably exceeds the level of resolution we have in the rock record.But what we can say is that it's the only place where you can really to establish where. Teilhardina appears in this climate event with confidence is in the Bighorn Basin. "
As the Earth warmed, plants and animals expanded their range northward, down to the south at the end of the PETM.
"This dance of plants and animals with climate change has occurred over vast landscapes, with forests moving from the Gulf Coast to the Rocky Mountains in just a few thousand years," Bloch said. .
Teilhardina probably followed the evolution of its forest habitats on the land bridges that then connected to North America, Greenland and Eurasia, he said.
"Teilhardina do not throw your bag over your shoulder and do not walk, "he said. Its range varies from one generation to the next. More than 1,000 years, you have a lot of movement, and over 2,000 to 3,000 years, you could easily travel continental distances. "
While it was well suited to the Earth's greenhouse environment, Teilhardina disappeared with the PETM, replaced by new physically distinct primates. It's a sobering reminder of what can happen to species – including humans – in times of rapid climate change, Bloch said.
"A changing planet has dramatic effects on biology, ecosystems, and evolution, and is part of the process that has produced the diversity of life we see today and mass extinctions of life. that have occurred periodically in the history of the Earth, "said Bloch. "One of the unexpected results of global warming 56 million years ago is that it was at the origin of the group that finally drove us in. The way we go about it will shoot in the future warming scenarios is less certain. "