New Evidence: Abrupt Climate Change Did Not Drive Neanderthal Extinction

Woods Hole Oceanographic Institution reports that new research by a multidisciplinary, international team shows that Neanderthals did not die out at a time of extreme and sudden climatic change.

Over time, scientists have offered more than one competing theory for what led to the extinction of the Neanderthals. Much scholarly debate focuses on the possible relative roles of climate change versus Neanderthal conflict with modern humans.

Thanks to new research and dating methodology, the theory propounding catastrophic climate change can be ruled out as a possible reason for the Neanderthals' extinction.

The innovative team of researchers, which included paleoclimatologist Konrad Hughen of the Woods Hole Oceanographic Institution, compared the dates of the final Neanderthal occupation of Gorham's Cave on Gibraltar with paleo-climatological records drawn from both Greenland ice cores and Atlantic seafloor sediments.

The location of Gorham's Cave is on Gibraltar's south side. It is considered to be the last known habitation of the Neanderthals. Sea level change has brought the Cave within meters of the Mediterranean Sea.

Ice cores and sedimentary records, such as those used by the researchers, allow scientists to derive information about past temperatures and the amount of moisture in the atmosphere. From this data they can establish a general description of global climate in an era or throughout history.

Events that are located in time through radiocarbon-dating may be difficult to calibrate exactly with calendar years. But geologic, climatological, and paleontological records can be mapped to each other allowing for specific time location of events.

The results of the team's comparison led Hughen and colleagues to conclude that two proposed dates, those being roughly 28,000 and 32,000 years ago, both fall within climate intervals that were neither particularly severe nor cold. This finding rules out the theory that Neanderthal extinction was due to abrupt global climate change.

More specifically, some theorists posit that Neanderthal extinction coincided with the Heinrich Events. These events correlated with initial warming during which vast quantities of icebergs spilled into the North Atlantic and blanketed the salty ocean water with fresh water. This fresh water disturbed the oceanic and atmospheric circulation and caused sudden global climate change that then abruptly precipitated reglaciation.

Tzedakis noted that "there are three main limitations to understanding the role of climate in the Neanderthal extinction: uncertainty over the exact timing of their disappearance; uncertainties in converting radiocarbon dates to actual calendar years; and the chronological imprecision of the ancient climate record."

"Our method circumvents the last two problems," said Hughen. Basically, the researchers did not attempt to relate the dates of the disappearance of Neanderthals to a calendar year. Instead they related the dates of the disappearance directly to what the climate record--ice cores and sedimentary records--indicates about the environment.

A different proposed theory of Neanderthal extinction suggests that the Neanderthals died out as recently as 24,000 years ago. This theory does show the extinction coincident with a period of major climate change. However, the climate change during this epoch was much more gradual and incremental than during the later suggested dates. Therefore the Neanderthals would have had time and opportuity to adapt and migrate as evidence indicates that they had done before.

This more recent, or younger, date "would imply a greater role of climate in Neanderthal extinction, not necessarily directly, but perhaps in the form of climate-driven intensified competition as a result of increased southward human migration from higher latitudes," the researchers wrote in their results that were published in the September 13 issue of the journal Nature.

The research analysis was led by Chronis Tzedakis of the University of Leeds; with contributions from Hughen, Isabel Cacho of the University of Barcelona, and Katerina Harvati of the Max Planck Institute for Evolutionary Anthropology

"News Release : Extinction of Neanderthals Was Not a Climate Disaster Scenario," Woods Hole Oceanographic Institution.