We have always assumed the modern apple was a cross of several wild species of Malus. Here’s an old article, from 2001, on the origins of the apple. There’s been more recent research, but this is still interesting.
The Garden
June, 2001

We may never know where the Garden of Eden was situated, but the origins of its most famous fruit – the apple – may have been discovered. Apples are so familiar in Britain that we assume they have always been part of our flora. Yet there is only one species of apple native to the British Isles, the spiny, wholly inedible Malus sylvestris. It is quite distinct in flavour, shape and genetic makeup for the eating apple, M. Domestica, which has been grown here since at least the Roman era. Botanists have nevertheless assumed that the domestic apple was a hybrid of crosses between the wild species that exist in northern temperate parts of the world.

This long-held ‘hybridization’ assumption has been challenged by the work over the last four years of botanist Barrie Juniper. Together with colleagues at Oxford University’s Department of Plant Sciences he has shown that the hybrid theory is almost certainly false and that the true genetic ancestors of all the apples we eat today seems to be a small population of a single species still growing in the remote Ili Valley on the northern slopes of the Tien Shan (the Heavenly Mountains) right on the border between northeast China and the former Soviet republic of Kazakhstan. He has also arrived at a plausible account of how, over perhaps the last 4.5 million years, this apple evolved within its mountain homeland to become larger and sweeter and, finally, how it was carried into western Europe by traders perhaps as early as the Neolithic period some 6,000 years ago.

Barrie explains that two unrelated factors in the last decade made these achievements possible. First, his department became equipped for sophisticated DNA comparison work. Second, the Russians and Chinese stopped nuclear testing in that area, allowing Barrie to launch two expeditions to hitherto inaccessible areas of the newly independent Kazakhstan.

One of the group, geneticist Julian Robinson, has been using DNA analysis to assess differences and similarities between Malus species, taking samples from pressed herbarium specimens and live material found in the Oxford Botanic Garden. ‘If they had assumed anything at all, botanists had assumed the apple came from some vague, undefined place in Central Asia and was crossed with one or more wild European species,’ said Barrie. The results of the analysis were something of a surprise therefore: far from containing genetic sequences from several species, it appears that the genetic material of only one species closely resembles what is known today as Malus domestica: M. Sieversii, a species of wild crab apple that replaces M. Sylvestris in Central Asia. ‘We came to the conclusion,’ Julian says, ‘that in all likelihood M. Domestica originated in Central Asia.’

Of all the regions where wild apples grow, south central China has the greatest number of different species. Although there are more than 20 true wild species of apple in southern, central and western China, most have small fruits, no bigger than a cherry. How then,Barrie asked himself, did they evolve into the big, red, juicy fruit that we enjoy today?

In search of paradise
Barrie began with a trip in autumn 1997 to Uzbekistan, north of Afghanistan, on which basis he led Julian Robinson and student biologist Thomas Ralis on their first expedition into Kazakhstan the following summer (funded by the Leverhulme and Merlin Trusts). Flying into the regional capital Alma-Ata or Almaty, meaning ‘father of apples’, they had, naively, expected to see wild apples growing in abundance, but instead of forests found scrubland in the country’s central region. This low vegetation of grass and small shrubs is the result of several thousand years of grazing by goats. More recent environmental change was caused by Stalin’s and Khrushchev’s attempts to introduce large-scale irrigated agriculture in the area.

Yet the Kazakh people with whom Barrie and his team spoke described fruit forests; local information suggested they drive northeast. With guides, they crossed some 970km (600 miles) of border country formerly frequented only by Russian and Chinese military, armed to the teeth, to reach the lower slopes of Dzhungarskiy Alatau, a string of mountains separated from the main Tien Shan range by the Ili Valley. They arrived in the dark to stay with a homestead family who combined farming with semi-military patrol duties at an altitude of 1,500m (5,000ft) and overlooking China. The next morning they stepped out of their ‘yurt’ (thick-walled traditional tent) and found they were in the heart of a malian wonderland. The apple trees, all Malus sieversii, grew to 9m, (30ft) high, hundreds of them, accompanied by a diverse selection of pear trees, apricots, plums and cherries. Every apple tree seemed to bear a different sort of fruit. Some were tiny and yellow like crab apples, others were round, red and as big as Bramleys, illustrating the great genetic diversity that seems characteristic of many apple species. ‘It was like a mad orchard, a huge tangle, full of old, dying trees and young seedlings,’ Barrie says.

After photographing the wild orchard, they collected three leaves from each tree, which were taken back to the laboratory in Oxford, preserved in silica gel, for DNA analysis. There they found a match between some genetic sequences in the samples of their Malus sieversii from Kazakhstan and modern apple cultivars. Comparison with other Malus species showed only remote evolutionary relationships that had occurred in the much more distant past.

The great Russian geneticist, NI Vavilov, is credited with the first suggestion that M. Sieversii might be the progenitor of the modern apples, as early as 1930, but conclusive proof was not then possible. Nor was Vavilov, in spite of his prestige, able at the time to get into that remote, disputed border region.

Barrie and his co-researchers had now shown pretty conclusively that the hybrid theory was wrong and the modern apple’s origins lay in the fruit forests of the Tien Shan. But they wanted to go back even further.

The next question was, how did fruit from a remote part of Asia end up domesticated thousands of miles away in Western Europe? The following year the team returned for more clues because ‘genes alone cannot provide the answer’. This time they entered the Ili Valley via China, and stopped by Urumqi, in the provinces of Xinjiang. Here they saw 4,000- 6,000 year-old human mummies unearthed from the edge of the Taklimakan desert. These individuals dating from the Neolithic and Bronze Age proved, to the surprise of archaeologists, to be not of Asian, but of Caucasian or Indo-European origin. Barrie’s team therefore had direct evidence from the mummies proving there was human traffic moving west-east-west, 6,000 years ago or more, forming a vital part of the jigsaw of the apple’s origins.

Combining the evidence
Barrie was now in a position to construct a complete, if hypothetical, evolutionary history of the apple. It runs thus: the original Malus, judging by the 20-plus species and their numerous varieties in central and southern China, evolved 10-20 million years ago and bore a small fruit with hard but edible seeds, probably similar to those of modern rowans. It was spread by birds through the northern hemisphere and our own wild crab apple is a descendant.

A key small group of wild apples penetrated northwest from their central Chinese stronghold along a fertile corridor, now the Gansu Province. Around 4.5 million years ago, the Tien Shan mountain range began pushing ever higher in the same mountainbuilding episode that created the Himalaya, caused by the collision of India with Asia. Birds took the seeds of one or possibly more species of Malus over the rising hills towards what is now Kazakhstan. Meanwhile, climate change was causing the arid Gobi and Taklimakan deserts to spread over Gansu, preventing movement back east so the Tien Shan apples were cut off and began to evolve in isolation.

As early as 7 million years ago, in the Ili Valley, forest deer, wild pigs and bears began to occupy the growing woodland, joined by wild horses and donkeys from the Steppes further west. All these herbivores would have gorged on the wild autumn fruit, selecting those individual trees producing larger, sweeter and juicier fruit. The apple therefore evolved in tandem to take advantage of these new means of distribution, growing even
larger and sweeter. Gradually it changed from a bird’s fruit with edible seeds to a much larger mammal’s fruit with poisonous seeds (apple pips contain cyanide). The seed coat became smooth, black and hard, and the seed itself became tear-shaped to pass unharmed more easily through the animals’ guts.

By the time the ‘new’ apple had populated the northern slopes of the eastern Tien Shan and reached what is now Almaty, it would have grown to something approximating its present qualities. Much later, after the end of the last ice age (around 10,000 years ago) humans began to travel the animal migratory routes east and west and took advantage of the new fruit.

Thus did the big, sweet apple move west. It was taken up and cultivated in progressively more sophisticated ways in Mesopotamia and around the Mediterranean. Apples cannot be raised from cuttings, so the first cultivated trees would have been grown from seed. Genetic variation would have meant the same size differences still found in the Ili Valley. It was not until the art of grafting was perfected that vegetative propagation of selected trees with the best fruit was possible. Whether or not seed-raised sweet apples reached these shores earlier, it was probably the Romans who brought the modern, grafted apple to Britain, where it found conditions so much to its liking it ultimately produced, as Barrie says, ‘the finest collection of dessert, culinary and cider fruits ever known’.

Barrie will be returning to the ancient fruit forest of which the world knows so little, for it may well hold the key to the origin of the other fruits they found there, the pears and cherries and plums and apricots, and perhaps even almonds and walnuts as well. ‘We’ve started with the apple. Hopefully, we will go on to establish the genetic history of the other fruits, too,’ he says.