New evidence in support of an extraterrestrial source behind an abrupt climate change event that occurred at the end of the last ice age has been found in Africa, according to a team of South African scientists. The discovery marks the first such evidence from the African continent found to-date.
12,800 years ago, the planet was undergoing some big changes. As the ice age was coming to an end, glacial ice was beginning to recede back toward the poles, and the Earth had gradually begun to warm. Then something caused the Earth to plunge back into a period of cooler temperatures, lasting more than 1000 years and affecting global weather patterns.
This period is known as the Younger Dryas, named for the flower Dryas octapetala, which grew in abundance during the cooler temperatures of the Pleistocene, and which researchers found again in abundance during this cold reversal period that occurred around 12,800 years ago.
Scientists initially argued that the Dryas had been the result of natural deglaciation processes. However, mounting evidence for an extraterrestrial cause has led many paleoclimatologists to consider whether there might have been more to this unusual period in Earth's history. Key evidence for this was discovered in the form of an anomalous spike in platinum--an element that is rare on Earth--which is found in abundance in geological layers associated with this period. One reason for such an abundance of a rare earth element could be a meteor impact or airburst.
Now, a team led by Professor Francis Thackeray of the University of Johannesburg's Evolution Studies Institute has discovered evidence for this unusual platinum abundance in Africa as well, EurekaAlert reports.
The platinum anomaly was discovered at the Limpopo Province near Pretoria, South Africa at Wonderkrater, a Middle Stone Age site comprised of a large spring and peat mound, which has proven rich in both archaeological and paleoclimatic information in past studies.
The platinum anomaly was discovered in a core from a peat deposit at the location dated to approximately 12,800 years ago, which coincides with the time at which the impact is believed to have occurred.
"Without necessarily arguing for a single causal factor on a global scale," Thackery noted in the study, "we cautiously hint at the possibility that these technological changes, in North America and on the African subcontinent at about the same time, might have been associated indirectly with an asteroid impact with major global consequences."
The discovery is significant due to the fact that it is the first evidence from Africa that supports the global disturbance caused by the Younger Dryas event, evidence for which was first uncovered in Europe, and thereafter in North America, South America, and Asia. In addition to climate changes, the events of the Younger Dryas were likely to have played a role in widespread megafaunal extinctions. Human populations were also affected, as indicated most prevalently in changes in the archaeological record coinciding with the American Clovis culture, which would have existed at the time of the Dryas.
"We cannot be certain," Thackery went on to say, "but a cosmic impact could have affected humans as a result of local changes in environment and the availability of food resources, associated with sudden climate change."
Thackery further states that the evidence obtained by the team "is entirely consistent with the Younger Dryas Impact Hypothesis." Thackery and his team's study appeared in Palaeontologia Africana.
Additional information on the Younger Dryas Impact Hypothesis can be found at the website of the Comet Research Group, an interactive source for information online which details the scientific evidence in support of the impact theory, in addition to promoting broader awareness of the potential threat future asteroid strikes may pose to humanity.