The mass extinction of large mammals or megafauna during the last Ice Age was caused by humans and not climate changes, according to an Aarhus University study.

"Our results strongly underline the fact that human expansion throughout the world has meant an enormous loss of large animals," Postdoctoral Fellow Søren Faurby said in a statement.

Prior to the finding, there were two theories propagated by scientists for the extinction.

One of the theories stated that large animals disappeared due to climate change, meaning most of the species were unable to find suitable habitats and as a result died. Since the extinction of large animals did not occur during previous Ice Ages, the disappearance of the species during the last Ice Age was mystifying to researchers.

The other theory claimed the loss of the animals was due to "overkill." Modern man spread from Africa to all parts of the world more than 100,000 years ago. Human hunting either decreased the animal population significantly or caused the loss of their prey.

For the study, the researchers did a global analysis and a minute mapping of all the large mammals that existed 132,000 to 1,000 years ago. They analyzed the geographical variation in the percentage of large species that became extinct on a much finer scale than previously managed.

The researchers found that a total of 177 species of large mammals vanished during this period. Africa lost 18 species, Europe 19, Asia 38, Australia 26, North America 43 and South America lost a total of 62 species of large mammals.

The disappearance of the large animals occurred in all climate zones. It affected cold-adapted species like woolly mammoths, temperate species like forest elephants and giant deer, and tropical species like giant cape buffalo and some giant sloths.

Holding climate change as a cause for the loss of large mammals during the last Ice Age is not feasible. In fact, the connection between climate change and the loss of megafauna was only observed in Eurasia (Europe and Asia).

"The significant loss of megafauna all over the world can therefore not be explained by climate change, even though it has definitely played a role as a driving force in changing the distribution of some species of animals. Reindeer and polar foxes were found in Central Europe during the Ice Age, for example, but they withdrew northwards as the climate became warmer," said Postdoctoral Fellow, Christopher Sandom.

On the other hand, the findings show a strong connection between the extinction and the history of human expansion.

"We consistently find very large rates of extinction in areas where there had been no contact between wildlife and primitive human races, and which were suddenly confronted by fully developed modern humans (Homo sapiens). In general, at least 30% of the large species of animals disappeared from all such areas," said Professor Jens-Christian Svenning.

The findings are published in the journal Proceedings of the Royal Society B.