Discovery in Africa: DNA can last 50,000 years in hot climates, says study
A recent study, published on May 27, revealed that researchers were able to extract genetic material from animals that lived in southern Africa during the last ice age, indicating that DNA can survive much longer in warm climates than previously imagined.
The team of scientists recovered DNA from a 50,000-year-old antelope tooth, setting a new record for the oldest genetic material ever found in sub-Saharan Africa.
This discovery suggests that DNA preservation in the region could occur for tens of thousands of years, a surprising fact given that the hot local climate often degrades the molecule, making it difficult to study the evolution of many species, including human ancestors.
More on this story: Discovery in South Africa reveals 50,000-year-old DNA and redefines preservation expectations
While some temperate areas are recognized for the conservation of ancient human DNA, such as the Sima de los Huesos in Spain, the sub-Saharan African environment is less conducive. Previously, the oldest human DNA in the region dated back around 18,000 years, and the oldest animal was just 9,300 years old.
How research into ancient DNA was carried out
In the most recent study, researchers investigated whether it would be feasible to extract DNA from even older skeletons. Analyzing more than 300 teeth from animals that lived in the last 110,000 years, they identified small amounts of DNA in remains from the Late Pleistocene, the final phase of the last ice age.
Published in the journal Quaternary Science Reviews, the research managed to extract DNA from dozens of bovid samples from the Holocene, less than 11,700 years old, and four specimens from the Late Pleistocene, between 12,000 and 50,000 years old. Although many teeth did not contain genetic material, some did. The oldest DNA was found in a partial molar of an African antelope, Redunca fulvorufula, discovered in Boomplaas Cave, in southern South Africa. Other ancient samples came from three extinct long-horned buffaloes, dating back to 21,000 and 12,000 years ago.
Initial skepticism and new evidence confirm finding
Deon de Jager, a paleogenomics expert at the University of Copenhagen and first author of the study, expressed some skepticism. “50,000-year-old DNA is exciting, but I’m skeptical myself, for two reasons,” he said.
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De Jager explained that the reedbuck’s DNA is much older than the next oldest sample (from the long-horned buffalo) and that the specimen was contaminated with human DNA, which could be removed. These issues make the result of the antelope’s 50,000-year-old DNA not completely guaranteed. However, since the study’s publication, researchers have sequenced the genome of a 42,000-year-old wildebeest in Ethiopia, reinforcing the idea that DNA lasts longer in the African climate than previously thought.
Learn more: Excavation in Greece reveals 430,000-year-old wooden artifacts used by ancient hominids
“There is a limit to DNA preservation in Africa, but it is not clear what it is,” said De Jager. “There are certainly parts of Africa where DNA will be preserved even better than in the places we researched. Deep caves with stable, low temperatures would be good candidates, as would high-altitude sites where temperatures have been very low for a long time.”
Importance of the discovery for evolutionary studies and its limits
The Late Pleistocene teeth analyzed by De Jager and his team contained very low amounts of DNA. The half-life of DNA is estimated to be about 521 years, meaning that half of it disappears every 521 years. However, the quantity found is still valuable, according to the expert.
DNA is sufficient to identify evolutionary lineages, allowing researchers to compare gene flow and interbreeding between species and populations if they can collect enough data.
While these results open new doors to understanding animal and human evolution in South Africa over the last 40,000 to 50,000 years, it is unlikely that it will be possible to extract DNA from ancient human relatives like Homo naledi, which became extinct around 240,000 years ago, or Paranthropus robustus, which disappeared approximately 1 million years ago.
“I think the chances of getting DNA from Homo naledi are very, very low, unfortunately,” commented De Jager. “You would have to be very lucky with an incredibly well-preserved skull, with the petrosal bone still intact, which is the best for getting ancient DNA. Getting DNA from something almost 1 million years old in Africa would probably be impossible, as the climatic conditions are so harsh.”
