The world’s oldest peach pits were discovered relatively recently in southwest China. They have been dated to be around 2.5 million years old, predating early man in the region. Though these pits look similar to present day ones, with long grooves along its sides, the fruit itself is believed to have been a lot smaller, somewhere around 2 inches (5 centimeters) in diameter.
“If you imagine the smallest commercial peach today, that’s what these would look like,” Peter Wilf, a professor of paleobotany at Pennsylvania State University, said in a statement. “It’s something that would have had a fleshy, edible fruit around it. It must have been delicious.”
Tao Su, a colleague of Peter Wilf, an associate professor at Xishuangbanna Tropical Botanical Garden in China’s Yunnan province, collected 8 such pits which were discovered by accident during a construction work near the North Terminal Bus Station in Kunming, the capital of the province. These pits were put through a battery of tests to see if they warn’t placed there recently, either intentional or by accident.
Instead they discovered these pits to be placed in a rock dating back to the Pliocene era, a geological period dating back from 5.3 to 2.6 million years ago.
By scanning the fossils at Penn State, Wilf and Su discovered that the seeds inside the pits had been replaced by iron and the walls of the pits had recrystallized —marks of old age. The researchers also attempted to date the peach fossils by looking at the amount of decaying carbon-14 they contained —a common way tomeasure the age of organic remains. But their results showed that the fossils were beyond the range of radiocarbon dating, which is currently about 50,000 years.
Peaches were already thought to be native to China, and historical sources attest that the fruit was cultivated in China for centuries. Peaches are mentioned in the Book of Songs, or Shi-Jing, China’s oldest known collection of poetry, with works dating from the 11th to seventh centuries B.C. Evidence of peach eating has also turned up at archaeological sites, such as a Neolithic settlement discovered in Hemudu village, in Zhejiang province, where peach pits that are about 8,000 years old were discovered in the 1970s.
The researchers on the new study, which was published online Nov. 26 in the journal Nature Scientific Reports, think their evidence shows that peaches evolved both under natural selection and later through human domestication.
Peaches were probably an attractive food source for fruit-eating primates, including human ancestors like the extinct Homo erectus and early Homo sapiens who arrived in China during the Pleistocene epoch. The earliest peach eaters might have even helped the plant species spread by inadvertently dispersing seeds through their feces, the researchers said.
“The peach was a witness to the human colonization of China,” Wilf said in a statement. “It was there before humans, and through history, we adapted to it and it to us.”
Though the researchers think the prehistoric peaches could be assigned to the same peach species living today (Prunus persica), they have proposed a new species name, Prunus kunmingensis, because they are not able to reconstruct the whole plant based on the pit alone.