Exploring the origins of the apple – ScienceDaily

The apple is probably the most famous fruit in the world. It is cultivated in temperate environments around the world and its history is deeply linked to humanity. The representations of large red fruits in classical art show that domesticated apples were present in southern Europe more than two thousand years ago, and ancient seeds of archaeological sites attest to the that people have been collecting wild apples in Europe and Western Asia for more than ten thousand years. . While it is clear that populations have closely maintained populations of wild apple trees for millennia, the process of domestication, or evolutionary change in human culture, among these trees is not clear.

Several recent genetic studies have demonstrated that the modern apple is a hybrid of at least four wild apple populations, and the researchers hypothesized that the Silk Road trade routes were responsible for the merger. of these fruits and their hybridization. Archaeological remains of preserved seeded apples have been found at sites in Eurasia. These findings support the idea that fruit trees and walnuts were among the commodities borrowed on these early trade routes. Spengler recently summarized the archeobotanical and historical evidence of cultures on the Silk Road in a book titled Fruit from the Sands, published by the University of California Press. The apple has a close link with the Silk Road – much of the modern apple's genetic material is sourced from the heart of the ancient trade routes of the Tien Shan Mountains in Kazakhstan. In addition, the exchange process provoked the hybridization events that gave birth to the large, sweet red berries in our product markets.

Understanding how and when apple trees have evolved to produce larger fruits is an important issue for researchers, as fruit trees do not seem to have followed the same path to domestication as other, better understood crops, such as cereals legumes. Many different wild and anthropogenic forces exert selective pressure on the crops of our fields. It is not always easy to reconstruct what pressures caused what evolutionary changes. Therefore, examining the evolutionary treatment in modern and fossilized facilities can help researchers interpret the domestication process. Sweet fleshy fruits evolve to attract animals to eat afterwards and spread their seeds; large fruits evolve specifically to attract large animals to disperse.

The big fruits have evolved to attract the old megafauna

While most researchers studying domestication focus on the period during which humans begin to grow a plant, Spengler explores in this study the processes in nature that have paved the way for domestication. Spengler suggests that understanding the process of evolution of large fruits in nature will help us understand the process of their domestication. "Seeing that fruits are evolutionary adaptations for seed dispersal, the key to understanding the evolution of fruits is to understand what animals ate in the past," he says.

Many fruit plants in the apple family (Rosaceae) have small fruits, such as cherries, raspberries and roses. These small fruits are easily swallowed by birds, which then disperse their seeds. However, some family trees, such as apples, pears, quinces and peaches, have evolved in the wild to become too big for a bird to disperse their seeds. Fossil and genetic evidence shows that these large fruits evolved several million years before humans began to grow them. So who did these big fruits evolve to attract?

Evidence suggests that large fruits are an evolutionary adaptation to attract large animals able to eat fruit and spread seeds. Some large mammals, such as bears and domesticated horses, eat apples and spread the seeds today. However, before the end of the last ice age, there were many more large mammals in the European landscape, such as wild horses and large deer. Evidence suggests that seed dispersal in wild relatives of the coarse apples has been low over the last ten millennia, with many of these animals extinct. The fact that wild apple populations appear to map glacial ice-cover areas also suggests that these plants did not move long distances or colonize new areas in the absence of their ice spreaders. seed of origin.

The trade along the Silk Road has probably allowed the development of the apple we know today

Wild apple populations were isolated after the end of the last ice age, until humans began to carry fruit across Eurasia, especially along the Silk Road. Once humans brought these lines of trees back into contact, bees and other pollinators did the rest of the work. The resulting hybrid offspring had larger fruit, common result of hybridization. Humans have noticed the largest fruit trees and corrected this trait by grafting and planting cuttings on the most favored trees. Thus, the apples that we know today have not been developed mainly through a long process of selection and propagation of the seeds of the most favored trees, but rather by hybridization and grafting. This process may have been relatively quick and some of its parts were probably unintentional. The fact that apple trees are hybrids and not "properly" domesticated is why we often end up with a wild apple tree when we plant an apple seed.

This study challenges the definition of "domestication" and demonstrates that there is no single model for explaining the evolution of plants in human culture. For some plants, domestication took millennia of culture and a selective pressure induced by humans – for other plants, hybridization caused a rapid morphological change. "The process of domestication is not the same for all plants and we still know little about the process in long-lived trees," notes Spengler. "When we study the domestication of plants, it is important that we examine past annual herbs, such as wheat and rice.There are hundreds of other domesticated plants on the planet, many of which have taken different routes to domestication. " In the end, the apple in your kitchen seems to owe its existence to megafaunal navigators and extinct Silk Road traders.