A new study published online in the journal Proceedings of the National Academy of Sciences sheds light into the cause of extinction of the last woolly mammoths. The last population of the extinct animals on an Alaskan island were wiped out by rising sea levels and the lack of fresh water.

The findings came from the analysis of sediment core from a lake on St. Paul Island. Apparently, the island underwent dry conditions and deteriorating water quality, killing the remnant woolly mammoths on the island thousands of years after the mainland population of mammoths died. The team also says that the mammoth bones and teeth confirm drier conditions in the area during this time.

The research team estimates that the remnant population of woolly mammoths became extinct around 5,600 years ago. St. Paul Island used to be bigger, but its size fell to 110 square kilometers due to rising sea levels. This event also made the mammoths unable to find new areas with fresh water.

However, the researchers assert that humans did not play a role in the woolly mammoth’s extinction on the island. The team did not find any evidence of people living here during the time of the mammoths.

“It paints a dire picture of the situation for these mammoths,” points out the study’s co-author Matthew Wooller, the director of the Alaska Stable Isotope Facility at the University of Alaska Fairbanks. “Freshwater resources look like the smoking gun for what pushed them into this untenable situation.”

The findings can also have implications to current wildlife living on St. Paul Island. The researchers assert that the island is prone to environmental changes.

The research was led by Russ Graham from Pennsylvania State University. Other collaborators of the study included a group of researchers from the US and Canada.