In the end it was too wet: The ice age climate change and not humans brought the mammoth to an end, according to a study. As a result of increasing moisture, the giants’ livelihoods disappeared: the typical vegetation of the mammoth steppe. This emerges from the examination of old environmental DNA. The study also documents that in addition to the known remnants of proboscis on Wrangel Island, mammoths also lived on the Siberian mainland until around 4,000 years ago. Accordingly, they were apparently able to coexist with humans for a long time until the change in vegetation brought about the end there too.
They are the symbolic animals of the Ice Age: the woolly mammoths are the most prominent representatives of the megafauna – the society of large animals that once populated the cold landscapes in the north of the world. The shaggy cousins of the elephants also lived side by side with our ancestors in the late phase of their era, as numerous finds show. But then the huge herds of animals increasingly disappeared from their former areas of distribution. According to finds, only remnants could last for some time: when the Egyptians built their pyramids, mammoths trudged across Wrangel Island in northern Siberia before the end came there too.
Climate or overkill?
“Scientists have been discussing what shaped the decline of the mammoths for 100 years. Humans were blamed for this because the animals had survived for millions of years without climate change processes being able to exterminate them. But when they lived with humans, they disappeared and so our ancestors were accused of chasing them to death, ”says Eske Willerslev of the University of Cambridge. But he and his colleagues advocate an alternative explanation: the animals could not cope with the special challenges posed by climate change at the end of the last ice age and therefore died out. They now see convincing evidence of this cause in the results of their current study.
Her focus was on studying the livelihood of mammoths and other now extinct representatives of the megafauna: Despite the cool conditions, the northern landscapes produced vegetation that could feed the large herbivores. Presumably their huge stomachs helped the mammoths with the digestion of the food and in winter they probably used their mighty tusks to shovel the food out of the snow. So far, however, it has remained unclear what characteristics the vegetation exhibited in the areas that offered the mammoths good living conditions and how the northern ecosystems changed in the course of the ice age climate change.
Environmental DNA provides insights
To gain further insight, Willerslev and his colleagues examined genetic traces of plants and animals from 535 different Arctic sites spanning the past 50,000 years. The team used the comparatively new method of examining environmental DNA: This also enables genetic traces to be detected that have penetrated the soil through animal excretions and skin cells. An important source of reference for the study was the analysis of the DNA of more than 1500 arctic plant species today.
As the researchers report, the typical mammoth steppe was characterized by a mixture of grasses, flowering plants and shrubs that is no longer found today. Wherever it dominated the landscape, the genetic traces of the mammoths and other representatives of the Ice Age megafauna were also found. At the end of the Pleistocene, however, a rapid change in the vegetation became apparent in many places, which was evidently associated with increasing wetness in the course of climatic changes. “As the climate warmed up, trees and marsh plants replaced the mammoth’s grassland habitats,” reports Willerslev. First author Yucheng Wang continues: “As the climate became more humid and the ice began to melt, lakes, rivers and swamps formed. The ecosystem changed, the biomass of the vegetation decreased and could no longer feed the mammoth herds, ”said the researcher.
Man apparently did not play a decisive role
The scientists also inserted their results into models to work out the importance of various factors. “Our results show that climate change, especially precipitation, is directly responsible for the change in vegetation. According to our models, humans had no influence on the decline of the mammoth, ”says Wang. Willerslev adds: “We were finally able to prove that not only was climate change the problem, but also the speed with which it was happening. The mammoths were unable to adapt quickly enough when the landscape changed dramatically and their food became scarcer ”.
The researchers were also able to gain insights into the fate of the last mammoth populations. Evidence of mammoth environmental DNA from samples from the Siberian Taimyr Peninsula shows that mammoths were there until around 4,000 years ago. This existence beyond the end of the Pleistocene 12,000 years ago is evidently due to the steppentundra vegetation of herbaceous plants that continued there for a long time. In view of the fact that humans have continuously colonized northern Eurasia for at least 16,000 years, these late surviving Taimyr mammoths also speak against the theory of a rapid overkill: Apparently there was a long coexistence between humans and mammoths in the last retreats, until the Change in vegetation robbed the animals of their livelihood.
Source: University of Cambridge, specialist article: Nature, doi: 10.1038 / s41586-021-04016-x