Round tomatoes, orange carrots, virtually seedless bananas and sweet oranges are not identical versions of the plants known to humans thousands of years ago. Most of what reaches fruit and vegetable departments today is the result of a long history of domestication, selection and hybridisation, during which people reshaped crops in terms of size, flavour, colour and productivity, and in some cases even their methods of reproduction.
Seed selection began reshaping crops
Most staple crops began to be domesticated between 3,000 and 10,000 years ago. Over successive generations, farmers kept the seeds of plants bearing the largest, tastiest, least bitter and most productive fruits, then replanted them.
As this process was repeated, larger and easier-to-harvest crops gradually emerged, thousands of years before modern genetic engineering. These changes were not the result of a single decision or brief experiment, but accumulated slowly as particular traits were selected in each growing season.
Over time, the form and composition of plants and their fruits changed, until some cultivated varieties differed greatly from the wild relatives from which their domestication began. Sweet oranges are an example of fruits that did not exist in their current form in nature, but were shaped through a complex history of hybridisation between different citrus lineages.
Sweet oranges are the product of citrus hybridisation
Genetic studies have shown that it combines genetic material from mandarins and pomelos, while a study published by Nature Genetics in 2025 offered a more detailed explanation of its origins. The study suggested that sweet oranges arose from an ancient hybridisation between bitter oranges and mandarins, while bitter oranges themselves carry genetic ancestry from mandarins and pomelos.
Researchers reinforced this view through artificial hybridisation experiments, illustrating the many stages that preceded the emergence of the sweet fruit known today. Oranges are not unique in this respect: some lemons, grapefruits and several modern citrus fruits emerged through repeated hybridisation.
Planting a seed taken from an orange does not guarantee a tree that retains the original fruit’s characteristics. Farmers therefore graft branches from desirable trees onto other rootstocks to preserve the traits of the same variety. The difference becomes even clearer when commercial bananas are compared with their wild relatives.
Parthenocarpy produced low-seed bananas
Wild bananas contain large, hard black seeds, and their fruits have only a limited amount of edible flesh. Modern bananas emerged after plants were selected for a combination of low fertility and the ability to form fruit without fertilisation, a phenomenon known as parthenocarpy. Generation after generation, this selection produced soft bananas that are almost free of hard seeds.
Genetic studies indicate that most cultivated varieties are descended mainly from two wild species: Musa acuminata and Musa balbisiana. Many modern dessert-banana varieties have 3 sets of chromosomes, a structure that explains their sterility and inability to reproduce naturally through seeds. But the ease of eating bananas is linked to an agricultural weakness.
Sterile varieties are propagated using suckers or tissue culture rather than seeds, making plants of the same variety highly similar genetically. As a result, a disease capable of infecting one plant can pose a threat to the rest of a genetically similar crop. Watermelons, too, were not always juicy, red and sweet.
Did selection change only the sweetness and flesh colour of watermelons?
Wild relatives include fruits that are bitter, have pale flesh and contain more seeds and less flesh. Genetic studies show that their domestication focused on enlarging the fruit, increasing its sweetness, changing the colour of its flesh and eliminating bitterness. Wild watermelons produce defensive compounds responsible for the bitter taste, but agricultural selection led to the absence of these compounds from cultivated watermelon fruits.
They did not disappear from the entire plant, however, and remain present in inedible parts, including the roots. Tomatoes, meanwhile, originate from wild plants in western South America, before moving to Central America and Mexico, where they underwent long periods of domestication and agricultural selection.
Some of their wild fruits weighed only a few grams and generally had two seed chambers. Selecting larger fruits over successive seasons produced modern varieties with multiple chambers, some of which can weigh about 1 kilogram. These varieties are dozens of times larger than their wild ancestors, with the increase reaching more than 100 times in some comparisons.
The changes to tomatoes did not stop at size, but also included shape, colour, skin firmness, ripening time, disease resistance and storage capacity. At times, however, the focus on abundant yields, ease of transport and longer shelf life came at the expense of some flavour and aroma characteristics.
The main origin of cultivated apples is linked to the wild apple Malus sieversii in Central Asia, particularly the area around the Tian Shan mountains in Kazakhstan. Modern apples are not simply larger versions of that ancestor, however: the movement of seeds and fruit east and west along ancient trade routes helped reshape them genetically.
During this journey, apple trees hybridised with other wild species, including the European wild apple. Genomic analyses have shown that the movement of apples along the Silk Road was also a route for hybridisation: varieties acquired traits from several wild populations, and people then preserved trees with distinctive characteristics through grafting.
Wild apples were highly diverse: some fruits were small, sour or astringent, while others were relatively large and sweet. There is therefore no single form that can be identified as “the first apple”, but rather a broad group of ancestors and lineages that contributed to the formation of cultivated varieties to varying degrees.
Research indicates that cucumbers were domesticated in India about 3,000 years ago from a smaller, more bitter wild relative. Over time, farmers selected plants with longer, fuller fruits and lower levels of cucurbitacin compounds, which cause bitterness in many plants of the cucurbit family. The genes for bitterness did not necessarily disappear completely from cucumbers, however.
Some plants can therefore produce bitter fruit when exposed to certain environmental stresses, or as a result of characteristics linked to the cultivated variety itself. Cultivated aubergine is thought to descend from an Asian wild species known as Solanum incanum, which had more thorns and smaller, more bitter fruits. As cultivation continued, people selected plants with fewer thorns and larger, better-tasting fruits.
This process led to great diversity in the shapes and colours of aubergines. They are no longer limited to the long purple fruit: varieties can be white, green or striped, as well as round or long. Its detailed history is still being studied, but evidence indicates that it passed through multiple stages of domestication and improvement in the Indian subcontinent, China and South-east Asia.
Not all fruit improvement dates back to ancient times; commercial kiwifruit provides a more recent example. Its widespread domestication began in the early 20th century, after its seeds were transferred from China to New Zealand. Over the following decades, farmers selected larger, better-tasting fruits that were more suitable for marketing, leading to the emergence of the global kiwifruit industry known today.
Agricultural selection has made many fruits and vegetables sweeter and less bitter. Humans are instinctively attracted to sweet tastes, while they avoid bitterness, which in nature may indicate the presence of defensive or toxic compounds. As a result, fruits with more sugars or lower levels of acids and bitter substances were repeatedly cultivated.
Greater size and productivity do not mean that all nutritional components increased at the same rate. In some cases, the proportion of water or starch rose and the fruit became larger without a corresponding increase in certain minerals and plant compounds. This can lead to a lower concentration of those elements when measured per 100 grams, a phenomenon known as the “dilution effect”.
Nutritional value, however, is not linked solely to selection and domestication. It is also affected by soil quality, fertilisers and irrigation, the timing of harvest and storage conditions, as well as rising levels of carbon dioxide in the atmosphere. Scientific reviews have recorded declines in the concentration of some nutrients in a number of crops, but the decrease does not occur at the same rate and does not affect all plants or all nutrients.
The domestication process was not a series of losses, however. Orange carrots, for example, are rich in carotenoids, while reducing bitterness has made many vegetables more acceptable and easier to eat. Increased crop productivity has also improved the ability to provide food for larger numbers of people.
Wild plants therefore cannot be considered superior in every respect. They may be richer in a particular compound, but they may also be smaller, more bitter and harder to digest, and may contain undesirable defensive compounds. Cultivated crops have gained size, flavour and ease of eating, while some varieties have, in return, lost part of the density of certain nutrients.
What people eat today is descended from ancient plants whose flavour, size, colour and methods of reproduction humans reshaped over thousands of years.
