What Did Tomatoes Originally Look Like?

The original wild tomato was a tiny, round berry roughly the size of a pea, weighing about one gram and growing on scraggly vines in the dry western slopes of the Andes. Compared to the hefty beefsteaks and plum tomatoes in grocery stores today, these ancestral fruits were almost unrecognizable. The journey from that small, bitter-tasting wild berry to the enormous, sweet tomato on your sandwich involved thousands of years of human selection, a surprisingly small number of genetic changes, and a domestication story that researchers are still piecing together.

The Wild Ancestor

The species most researchers point to as the tomato’s closest wild relative is Solanum pimpinellifolium, a plant that still grows wild in parts of South America. Its fruits average about one gram each, meaning you could fit several of them on a single fingertip.¹ These berries were round, smooth-skinned, and grew in loose clusters. By contrast, modern cultivated varieties can exceed 1,000 grams per fruit, making the domesticated tomato roughly a thousand times heavier than its wild progenitor.²

Between the fully wild species and the modern supermarket tomato sits an intermediate form, Solanum lycopersicum var. cerasiforme, sometimes called the cherry tomato type. This semi-domesticated variety likely represents an early stage of human selection. It still grows in a semi-wild state across parts of Central and South America and produces small, cherry-sized fruits that are notably larger than wild S. pimpinellifolium but far smaller than fully domesticated types.³ If you have ever grown currant tomatoes in your garden, those tiny bursting fruits are the closest commercially available thing to what the original wild tomato looked and tasted like.

Where the Original Tomato Grew

Wild tomato species are native to a surprisingly harsh environment. Rather than lush tropical forests, these plants evolved along the western coast of South America, from southern Ecuador through Peru and into northern Chile. Several related wild species thrive in conditions that would kill most garden plants: extreme aridity, high soil salinity, and dramatic temperature swings between scorching days and cold nights in the high Andes.⁴

Wild tomato populations tend to be geographically fragmented, clinging to stream drainages along the Andean and coastal mountain ranges. This patchwork distribution meant that different wild populations were somewhat isolated from each other, which contributed to the diversity of wild tomato species. Some tolerate near-desert conditions, while others survive freezing temperatures at high elevations. The toughness of these plants in extreme environments is part of why breeders still turn to wild tomato species today when they need genetic traits that modern cultivated varieties have lost.

Color, Ripening, and the Green Question

People often assume early tomatoes were green, and there is a kernel of truth to that, but the picture is more nuanced. Wild tomato species are predominantly green when unripe, like most modern varieties. When they ripen, they typically turn red or orange, driven by the same carotenoid pigments (especially lycopene) that make modern tomatoes red.⁵ So the ancestral wild tomato was a tiny red or reddish-orange berry at maturity, not a permanently green fruit.

That said, certain wild varieties and some domesticated lines retain green coloration even when fully ripe, a trait controlled by specific genetic factors. This “green-ripe” phenomenon occurs in scattered wild populations and is now understood to involve particular gene variants that block the normal ripening color change.⁵ The diversity of fruit colors we see in heirloom tomatoes today, from yellow and orange to deep purple and striped green, largely emerged through centuries of human selection and occasional mutations rather than reflecting the original wild state. The wild original was most likely a simple, bright red little berry.

Bitter, Toxic, and Built to Survive

If you could taste an unripe wild tomato, you probably would not enjoy it. Wild tomato fruits contain steroidal glycoalkaloids, a class of chemicals that are bitter and genuinely toxic to humans in large amounts. The primary one in tomatoes, called α-tomatine, is present at high levels in unripe fruit and serves as a chemical defense against insects, birds, and small mammals that might eat the fruit before the seeds are ready for dispersal.⁶

As the fruit ripens, those toxic compounds are chemically converted into nontoxic forms. In modern cultivated tomatoes, the shift from bitter α-tomatine to a harmless compound called esculeoside A happens during ripening, making the ripe fruit safe and palatable.⁷ This chemical switch is not just a quirk of biochemistry; it represents a clever evolutionary strategy. The plant poisons its own fruit while the seeds are immature to keep animals away, then detoxifies the fruit once the seeds are viable, essentially inviting animals to eat the fruit and spread the seeds.

Domestication accelerated this detoxification process. Research has shown that changes in how certain genes are chemically regulated, through a process involving DNA demethylation, helped drive the shift toward lower toxicity during tomato domestication.⁷ In practical terms, early humans selecting tomatoes that tasted less bitter were inadvertently selecting for plants with better chemical detoxification in their ripe fruit. This is why even today, eating green (unripe) tomatoes in large quantities can cause stomach upset: the ancestral defense chemistry has not been entirely bred out.

How a Pea-Sized Berry Became a Pound of Fruit

The thousand-fold increase in fruit size from wild to modern tomato is one of the most dramatic changes in any domesticated crop, and it happened through a surprisingly small number of genetic changes. Rather than thousands of genes shifting gradually, researchers have identified a handful of key mutations that account for most of the size increase.²

Two main processes drove the enlargement. The first involves how quickly and how often cells divide inside the developing fruit. A gene called fw2.2 acts as a brake on cell division; mutations that weakened this brake allowed cells to multiply more, producing larger fruit. The second process involves how many seed compartments (called locules) the fruit contains. Wild tomatoes typically have just two, giving them their round, simple shape. A mutation in a gene called fasciated increased the number of these compartments, creating the deeply lobed, irregular shapes seen in large beefsteak-type tomatoes.² Together, more cells per fruit and more compartments per fruit account for much of the dramatic size difference between ancestral and modern tomatoes.⁸

This means that the massive beefsteak tomato in your kitchen is essentially the same plant as its wild ancestor, with just a few critical genetic dials turned up. The underlying cellular machinery is nearly identical; what changed is how much of it runs and for how long during fruit development.

A Two-Step Domestication Journey

The path from wild berry to cultivated crop was not a single event but happened in at least two major stages, separated by geography. The prevailing model holds that the first transition occurred in South America, where people began selecting larger-fruited forms from wild S. pimpinellifolium, gradually producing the semi-domesticated cherry-type tomato. The second transition happened in Mesoamerica, likely in what is now Mexico, where these intermediate forms were further selected into the fully domesticated tomato with large, fleshy fruit.⁹

This two-step model is clean and elegant, but genomic research has complicated it. Analysis of DNA from hundreds of tomato varieties suggests the domestication history was messier than a straight line from wild to intermediate to cultivated. There appear to have been multiple waves of migration, mixing between wild and semi-domesticated populations, and selection events happening in parallel in different regions.³ The tomato’s domestication, in other words, was less like a relay race with a clean handoff and more like a tangled web of human movement and plant selection across a continent.

What the First European Tomatoes Looked Like

When tomatoes arrived in Europe in the early 1500s, they were already a domesticated crop, not raw wild plants pulled from the Andes. But they looked nothing like what we grow today. Historical herbarium specimens and botanical illustrations from the sixteenth century reveal that the earliest European tomatoes came in a much wider variety of colors, shapes, and sizes than historians previously assumed.¹⁰

Some had simple, five-petaled flowers and small, smooth, spherical fruits, looking much like a modern cherry tomato. Others had doubled-up petals, protruding styles, and deeply furrowed, segmented fruits that resembled a lumpy, lobed pumpkin more than a sleek Roma. The very first tomato described in European writing, by the Italian physician Matthioli in 1544, was a segmented type, which tells researchers that at least some of the tomatoes arriving in Europe had already undergone significant domestication in the Americas, including the mutations affecting compartment number that produce that ribbed, irregular shape.¹⁰

Colors in these early European tomatoes ranged widely. Yellow and golden forms were common enough that the Italian name “pomo d’oro” (golden apple) stuck, and red, orange, and multicolored forms also appeared. The uniform deep-red globe that dominates modern commerce was a much later development, shaped by centuries of selective breeding and, eventually, industrial agriculture’s preference for uniformity.

Changes You Would Not See at a Glance

Beyond fruit size, shape, and color, domestication reshaped the tomato plant in subtler ways. Wild tomato species are typically outcrossers, meaning they rely on pollen from other plants to set fruit. Their flowers have a structural feature called stigma exsertion, where the female part of the flower protrudes beyond the male parts, making self-pollination difficult and cross-pollination by insects more likely. Domesticated tomatoes have much shorter stigma exsertion, allowing the flowers to self-pollinate reliably without insect help.¹¹

This shift toward self-pollination was enormously practical for farmers. A plant that can pollinate itself does not depend on the right insects being present at the right time, and it breeds true more reliably from seed. But it came at a cost: self-pollinating plants shuffle their genes less, which over many generations narrows the gene pool. This is part of why domesticated tomatoes are genetically much less diverse than their wild relatives, a vulnerability that breeders are now working to address.

Leaf shape changed too. Domesticated tomato leaves are larger, more lance-shaped, and more deeply lobed and serrated than those of wild relatives, which tend to have smaller, rounder, smoother leaves.¹² If you placed a wild tomato plant next to a modern garden variety, the leaf differences alone would make them look like different species, even before you noticed the fruit.

What Modern Breeding Lost

The intense focus on yield and uniformity over the past half-century has had unintended consequences. Breeding tomatoes for high production, firm shipping texture, and long shelf life indirectly reduced flavor and nutrient content. This happened because flavor in tomatoes is biochemically complex, involving dozens of volatile compounds, sugars, and acids that interact in ways breeders were not specifically tracking. When you select hard for one trait like yield or firmness, other genetically linked traits can drift in the wrong direction without anyone noticing until the tomato reaches the consumer’s mouth.¹³

This is the origin of the common complaint that supermarket tomatoes taste like nothing. It is not your imagination and it is not just nostalgia. The genetics behind that bland flavor are now well-documented, and ironically, some of the missing flavor compounds still exist in the wild relatives that modern breeding left behind.

Wild Tomatoes as a Genetic Rescue Squad

The narrow genetic base of cultivated tomatoes makes them vulnerable to diseases, and breeders have repeatedly gone back to wild species to find resistance genes. Most of the major disease resistance in modern tomato varieties, including resistance to viruses, fungi, bacteria, and root-damaging nematodes, originally came from wild tomato species and was bred into cultivated lines through traditional crossing.¹⁴ Resistance to Fusarium wilt, one of the most economically damaging tomato diseases worldwide, has been introgressed from wild species for each of the three known races of the pathogen.¹⁵

This creates an interesting irony. The same tiny, bitter, tough wild plants that early farmers spent millennia transforming into something edible are now the essential source of genetic material that keeps the modern tomato industry from collapsing under disease pressure. The wild ancestors we “improved” away from are the ones we keep needing to go back to.

Re-Domesticating the Wild Tomato with Gene Editing

One of the more striking recent developments in tomato science flips the domestication story on its head. Instead of continuing to tweak cultivated tomatoes that have already lost most of their wild genetic diversity, a research team used gene editing to re-domesticate a wild tomato from scratch. By targeting just six genes in Solanum pimpinellifolium, the same tiny-fruited wild species that started the whole domestication saga, they produced plants with altered shape, larger and more numerous fruits, and improved nutritional content, while retaining the wild species’ natural disease resistance and stress tolerance.¹⁶

The approach essentially compressed thousands of years of selective breeding into a targeted set of genetic changes. The resulting plants were not identical to modern cultivated tomatoes but represented a kind of parallel-universe domestication: the same wild starting point, steered toward productivity through precise edits rather than centuries of trial and error. The fruits were still smaller than commercial varieties, but they carried traits that breeders have spent decades trying to reintroduce from wild relatives. Whether this strategy scales to commercial agriculture remains to be seen, but it underscores just how few genetic changes separate a wild weed from a productive crop plant, and how much of the original tomato’s character could be preserved if domestication had taken a different path.

1
Genetics. Dissecting the Genetic Pathway to Extreme Fruit Size in Tomato Using a Cross Between the Small-Fruited Wild Species Lycopersicon pimpinellifolium and L. esculentum var. Giant Heirloom
2
PubMed. Regulatory change in YABBY-like transcription factor led to evolution of extreme fruit size during tomato domestication
3
PubMed Central. Haplotype analyses reveal novel insights into tomato history and domestication driven by long-distance migrations and latitudinal adaptations
4
Euphytica. Distribution, ecology and reproductive biology of wild tomatoes and related nightshades from the Atacama Desert region of northern Chile
5
PubMed Central. Green ripe fruit in tomato: unraveling the genetic tapestry from cultivated to wild varieties
6
PubMed. Proteinase inhibitors I and II in fruit of wild tomato species: Transient components of a mechanism for defense and seed dispersal
7
PubMed Central. Removal of toxic steroidal glycoalkaloids and bitterness in tomato is controlled by a complex epigenetic and genetic network
8
PubMed Central. Genes that influence yield in tomato
9
PubMed Central. Genomic Evidence for Complex Domestication History of the Cultivated Tomato in Latin America
10
PubMed Central. Sixteenth-century tomatoes in Europe: who saw them, what they looked like, and where they came from
11
The Plant Cell. From non-self to self: stepwise mutations in transcription factors promote the transition to self-pollination in tomato
12
PubMed Central. Resolving Distinct Genetic Regulators of Tomato Leaf Shape within a Heteroblastic and Ontogenetic Context
13
Cell Press / Trends in Genetics. Breeding value: the value of crop wild relatives for the genetic improvement of tomato flavor
14
Genetic Resources. The role of tomato wild relatives in breeding disease-free varieties
15
PubMed Central. Breeding for Resistance to Fusarium Wilt of Tomato: A Review
16
PubMed. De novo domestication of wild tomato using genome editing