The successful dating of the most ancient genetic material yet may allow scientists to use preserved DNA from sources such as mammoth dung to help paint a picture of past environments.

An international research effort led by Eske Willerslev of the University of Copenhagen in Denmark reports in today’s issue of the journal Science it has extracted well preserved animal and plant DNA from sediments deep in the permafrost of northeastern Siberia.

Among the samples was the oldest DNA ever found – about 300,000 to 400,000 years old – as well as DNA from 28 families of trees, shrubs, herbs and mosses. Animal DNA dominates the sediments, and the researchers suspect this is because it is from the copious dung that animals such as mammoths would have produced.

Previously, most of what we know about ancient environments has come from analysing hard or soft tissue remains of plants and animals – such as frozen mammoth flesh, or animal tissue trapped in amber. But there are various problems with using DNA from hard or soft tissues, including contamination. Sedimentary DNA on the other hand is more widespread and can be dated more accurately.

“Sedimentary DNA provides a unique opportunity to assess the accuracy of pollen-based paleoenvironmental records,” write the authors.

The study has already settled one argument over what the area in northeastern Siberia, formerly known as Beringia, looked like around 20,000 years ago. Based on different fragments of evidence there have been many different interpretations. It has been described as a “sparse and poorly productive polar-desert unable to support a diverse magafauna”; to a “dense herb-dominated steppe/tundra supporting populations of bison, horse and mammoth”; and even “a mosaic of different tundra types”.

However, the DNA from numerous herbs found in the latest study, “clearly indicates a herb-dominated community with populations of bison, horse, musk ox and mammoth”, said the authors.

The DNA recovered from sediments may also help answer one of the greatest mysteries of the ancient world: why the mammoths died out. The sediments showed that grasses declined after the last ice age, 16,000 to 22,000 years ago, and were replaced by sedges. Perhaps, speculate the authors, these mainly water-dwelling plants, which include the Chinese water chestnut and Egyptian papyrus, signalled a critical shift in climate.

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