DNA reveals apples’ mixed ancestry – Alice Roberts

The news that most of us carry some Neanderthal DNA has its parallels in the world of apples. Domestic apples such as Tom Putt and Kingston Black were long thought to have developed from the crab apple, Malus sylvestris, then it seemed that their true ancestor was Malus sieversii, a wild species named after the 18th-century German botanist Johan Sievers who found it in what is now Kazakhstan. Now, it looks as though both species have been mixing it up for millennia.

Crab apples found in oldest human settlement

Traces of crab apples have been discovered at sites dating from the Mesolithic in Scotland and even further back – 25,000 years – in Dolní Věstonice in the Czech Republic, the oldest known permanent settlement. ‘While crab apples seem to have formed part of the “paleo diet”, there were other uses for them — medicinally and in cider-making,’ writes TV anthropologist Alice Roberts in her book Tamed – Ten Species that Changed our World (Penguin)

Alice Roberts

Anthropologist Alice Roberts followed the apple’s DNA trail 

In 1790, ‘Sievers found forests of huge apple trees laden with unusually large and colourful fruit,’ growing on trees up to 60 feet (20m) high on the slopes of the Tian Shan or the Heavenly Mountain, Roberts writes. And in the 1990s scientists tracing their mitochondrial DNA seemed to prove a direct and almost unsullied ancestral link with Malus sieversii, with origins between 4000 and 10,000 years in the past.

‘Similarities in the shape of trees and their flowers and fruit, together with clues from written history all pointed to the foothills of the Tian Shan as the birthplace of domesticated apples, Malus domestica,’ Roberts writes.

DNA shows two-way gene flow between ancient apples

But then, in 2012, the French geneticist Amandine Cornille analysed the DNA of a large number of apple species from China to Spain more completely. While she traced their ancestry back to Malus sieversii, her research also revealed that ‘the influence of other world apples – particularly Malus sylvestris, the European crab apple – has been profound,’ says Roberts. ‘The study showed that our modern, domesticated apples actually owe more of their genetic make-up to crab apples than to the original central Asian apples.’

The gene flow has been in both directions, apparently. ‘Cultivated apples did indeed come from the wild apples of Kazakhstan – but not exclusively… cultivated apples had clearly bred with wild crab apples as the cultivars [were] spread along the Silk Road,’ not only by humans but also by horses.

Invasive species? Romans and Normans

Malus sieversii

Malus sieversii

As Liz Copas wrote in Cider Apples – The New Pomona, even before the Romans invaded Britain bringing Malus pumila, other travellers from the Mediterranean to our western shores may have brought apples with ‘Khazak blood’ since ‘traffic from Asia Minor through the fertile crescent was well established before then.’

European crab apple

Malus sylvestris, Rosaceae

A thousand years later, ‘Normans brought over some of their apple varieties and by the 13th century when cidermaking was a widespread pursuit, codlins, custards, and reinettes came to our orchards’ Copas noted. ‘All our present-day apples, eaters, cookers and ciders, come from these common origins – the wild crabs.

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