New geological evidence from an international team of researchers - including Professor of Geological Sciences Peter Schultz - suggests that the drop in woolly mammoth populations about 13,000 years ago may have been caused by extraterrestrial impacts.
At the end of the Pleistocene epoch, the Earth was populated by a host of very large mammals including the woolly mammoth, mastodon, giant sloth and saber-tooth tiger. However, many of these species vanished from the fossil record about 12,900 years ago.
These mysterious disappearances have been the subject of Schultz's research, and he was brought in as an impact specialist to fact-check for the National Laboratory team, he told The Herald.
The group of researchers - led by Richard Firestone of Lawrence Berkeley National Laboratory - theorize that these mass extinctions were caused by earth's collision with one or more extraterrestrial objects. The impacts with these comets or meteorites caused worldwide climate changes, triggering the end of many of the large mammals.
The team discovered clues to these events hidden in a layer of the Earth's fossil record called the "black mat."
This three-centimeter-deep, carbon-based mat has been found in over 50 locations in North America alone and in many other locations worldwide.
The layer's formation coincided with the beginning of the "big freeze," an abrupt phase of climate change in the Earth's geological history. The team suggested that the mat might be related to the mass extinctions, leading them to further explore the formation.
Researchers found rare chemicals and compounds like iridium and nanodiamonds in the mat, which they say are evidence of an extraterrestrial impact. Nanodiamonds - microscopic fragments of diamonds - are the most telling discovery, as they can only be formed through an event such as the intense pressure of an extraterrestrial object colliding with Earth.
Schultz said the evidence is not definitive and more research needs to be done. Researchers know the impact event occurred, but they do not know for sure how it occurred. The site of impact, the number of objects that fell and the trajectory of these objects remain unknown.
But if this new theory is supported by additional evidence, it may indicate that such an impact event may have caused profound changes to human cultural development. One major question left to be answered is if the extraterrestrial object hit an ice sheet when it collided with Earth, Schultz said.
Schultz said the new theory could have profound impact on geology as well as on other fields of science. Evolutionary biologists may find an explanation for the disappearances of apparently well-adapted species, and anthropologists may find a clue to the source of some of the earliest myths of mankind, as well as why certain groups of people decided to migrate.
Schultz said the new theory "makes your mind spring in terms of possibilities," although further research is needed to fully confirm the theory. He said this particular area of study is growing quickly and that many students are entering it.
Schultz was assisted by Brown graduate student R. Scott Harris GS, a specialist in petrology. The research by Schultz and his team was funded by the National Science Foundation and the U.S. Department of Energy.
