The wild ancestor of Malus domestica is Malus sieversii. It has no common name in English, but is known in Kazakhstan, where it is native, as 'alma'; in fact, the region where it is thought to originate is called Alma-Ata, or 'father of the apples'. This tree is still found wild in the mountains of Central Asia in southern Kazakhstan, Kyrgyzstan, Tajikistan, and Xinjiang, China. For many years, there was a debate about whether M. domestica evolved from chance hybridisation among various wild species. Recent DNA analysis by Barrie Juniper, Emeritus Fellow in the Department of Plant Sciences at Oxford University and others, has indicated, however, that the hybridisation theory is probably false. Instead, it appears that a single species still growing in the Ili Valley on the northern slopes of the Tien Shan mountains at the border of northwest China and the former Soviet Republic of Kazakhstan is the progenitor of the apples we eat today. Leaves taken from trees in this area were analyzed for DNA composition, which showed them all to belong to the species M. sieversii, with some genetic sequences common to M. domestica.[citation needed] Some individual M. sieversii, recently planted by the US government at a research facility, resist many diseases and pests that affect domestic apples, and are the subject of continuing research to develop new disease-resistant apples. Other species that were previously thought to have made contributions to the genome of the domestic apples are Malus baccata and Malus sylvestris, but there is no hard evidence for this in older apple cultivars. These and other Malus species have been used in some recent breeding programmes to develop apples suitable for growing in climates unsuitable for M. domestica, mainly for increased cold tolerance.[citation needed] Apple cut horizontally, showing seedsThe apple tree was perhaps the earliest tree to be cultivated, and apples have remained an important food in all cooler climates. To a greater degree than other tree fruit, except possibly citrus, apples store for months while still retaining much of their nutritive value. Winter apples, picked in late autumn and stored just above freezing, have been an important food in Asia and Europe for millennia, as well as in Argentina and in the United States since the arrival of Europeans.[citation needed] The word 'apple' comes from the Old English word ęppel, which in turn has recognisable cognates in a number of the northern branches of the Indo-European language family. The prevailing theory is that 'apple' may be one of the most ancient Indo-European words (*abl-) to come down to English in a recognisable form.[citation needed] The scientific name malus, on the other hand, comes from the Latin word for apple, and ultimately from the archaic Greek malon (melon in later dialects). The legendary placename Avalon is thought to come from a Celtic evolution of the same root as the English 'apple'; the name of the town of Avellino, near Naples in Italy is likewise thought to come from the same root via the Italic languages. Linnaeus assigned the apple to the genus Pyrus, along with pears and quinces. Philip Miller subsequently separated the apple into its own genus, a division repeatedly ratified over the years.