Many theories have tried to explain the disappearance of Neanderthals, but a new one hits close to home for modern humans: climate change.

At one point, people were on the winning side of the shifting climate. A new research suggests that ancient cold, dry periods played a role in the extinction of the Neanderthals, helping the Homo sapiens to replace them and eventually become the only surviving human species.

Climate Change Edges Neanderthals Out

In a new study published in the journal Proceedings of the National Academy of Sciences, scientists found that stretches of cold, dry climate coincided with the disappearance of the ancient hominins, Neanderthals, in various parts of Europe. These periods were then followed by the appearance of Homo sapiens.

"Whether they moved or died out, we can't tell," Michael Staubwasser of the University of Cologne in Germany said in a statement.

Staubwasser and the rest of the team analyzed new and existing climate, as well as the archaeological and ecological data for the research. Two cold and dry periods were highlighted in the study: one lasted about 1,000 years that occurred 44,000 years ago and a second one that lasted 600 years about 40,800 years ago.

These climate events matched up with the time the Neanderthal artifacts began to disappear and Homo sapiens clues started to surface in sites within the Danube River valley and France.

The scientists suggest that the climate shift would have transformed the landscape from a forest into a shrub-heavy grassland. This type of setting is better suited to the highly adaptable Homo sapiens, which explains their sudden appearance.

"As has been said before, our species didn't outsmart the Neanderthals," Rick Potts of the Smithsonian Institution, who wasn't involved in the study, said in an e-mail. "We simply outsurvived them. The new paper offers much to contemplate about how it occurred."

The Neanderthals

Neanderthals, along with other hominins, lived throughout Europe and Asia hundreds of thousands of years ago. They disappeared around 40,000 years ago alongside another hominin species, Denisovans, leaving Homo sapiens as the only existing humans on Earth.

There are many theories about what happened on the extinction of the Neanderthals, including diseases, natural disasters, and tendency to be less adaptable than the surviving Homo sapiens. The shifting climate may have been the final blow to the Neanderthals' dwindling population.

Not everyone is convinced that the periods of climate shifts caused the ultimate demise of the hominins, though. According to Katerina Harvati, a Neanderthal expert at the University of Tuebingen who was not involved in the study, it is unclear if the Neanderthals and Homo sapiens appeared and disappeared at the times the authors have noted as the evidence is quite limited and could be disputed.