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Grapes have been closely linked to human history for millennia, providing the basis for the wines produced by our ancestors thousands of years ago – but that might not have been the case if dinosaurs had not disappeared from the planet, according to new research.
When an asteroid hit Earth 66 million years ago, it wiped out the massive, heavy animals and paved the way for other creatures and plants to flourish.
The discovery of fossilized grape seeds in Colombia, Panama and Peru that are 19 million to 60 million years old is shedding light on how these humble fruits gained a foothold in Earth’s dense forests and eventually became established globally. One of the newly discovered seeds is the oldest example of a grape family plant found in the Western Hemisphere, according to a study of the specimens published Monday in the journal Nature Plants.
“These are the oldest grapes ever found in this part of the world, and they are a few million years younger than the oldest grapes ever found on the other side of the planet,” Fabiany Herrera, lead author of the study and assistant curator of paleobotany at the Field Museum at the Negaunee Integrative Research Center in Chicago, said in a statement. “This discovery is important because it shows that after the dinosaurs went extinct, grapes really started to spread around the world.”
Like the soft tissues of animals, fruits themselves don’t preserve well in the fossil record. But seeds, which are more likely to fossilize, can help scientists understand which plants were present at different stages of Earth’s history, piece together the tree of life, and establish origin stories.
The oldest grape seed fossils discovered so far were found in India and date back 66 million years, around the time the dinosaurs disappeared.
“We always think about animals, dinosaurs, because they were the ones that were most affected, but the extinction also had a huge impact on plants,” Herrera said. “The forest regenerated in a way that changed the composition of the plants.”
Steven Manchester, Herrera’s PhD advisor and lead author of the new study, published a paper on grape fossils found in India. It prompted Herrera to wonder where else grape seed fossils might exist, such as in South America, although they have never been found there.
“Grapes have been known for 50 million years, so I wanted to find one in South America, but it was like looking for a needle in a haystack,” Herrera said. “I’ve been looking for the oldest grape in the Western Hemisphere since I was an undergraduate.”
Herrera and Mónica Carvalho, a co-author of the study and an assistant curator at the University of Michigan Museum of Paleontology, were doing fieldwork in the Colombian Andes in 2022 when Carvalho spotted a fossil. It turned out to be a 60-million-year-old grape seed fossil trapped in rock, one of the oldest in the world and the first to be discovered in South America.
“She looked at me and said, ‘Fabiany, a grape!’ And then I looked at her, and I was like, ‘Oh my God.’ It was so exciting,” Herrera said.
Although the fossil was tiny, its shape, size and other characteristics allowed the duo to identify it as a grape seed. Back in the lab, the researchers performed CT scans to study its internal structure and confirm their findings.
Fabiany Herrera
Mónica Carvalho can be seen holding the first grape recently discovered in the Western Hemisphere at the excavation site in Colombia.
They named the newly discovered species Lithouva susmanii, or “Susman’s stone grape,” in honor of Arthur T. Susman, who was a strong proponent of South American paleobotany at the Field Museum.
“This new species is also important because it supports a South American origin of the group in which the common grapevine Vitis evolved,” said study co-author Gregory Stull of the National Museum of Natural History.
The rocks were deposited in ancient lakes, rivers and coastal areas, Herrera said.
“To look for such tiny seeds, I crack open every piece of rock available in the field,” he said, adding that the difficult search “is the fun part of my job as a paleobotanist.”
Encouraged by this discovery, the team continued their field research in South and Central America and discovered nine new species of fossilized grape seeds trapped in sedimentary rocks. By tracing the lineage of ancient seeds back to their modern counterparts, the team realized that something had allowed these plants to thrive and spread.
When the dinosaurs disappeared, their absence changed the entire structure of the forests, the team hypothesized.
“We know that large animals, like dinosaurs, change the ecosystems around them. We think that if large dinosaurs were roaming the forest, they were probably cutting down trees, which allowed the forests to be more open than they are today,” Carvalho said.
After the dinosaurs disappeared, rainforests were overgrown, and layers of trees created an understory and canopy. These dense forests made it difficult for plants to access light, which had to compete with each other for resources. Climbing plants had an advantage and used it to reach the canopy, the researchers explained.
“In the fossil record, we’re starting to see more plants that use vines to climb trees, like grapevines, around this time,” Herrera said.
Meanwhile, as a diverse set of birds and mammals began to populate the Earth after the dinosaurs disappeared, they likely also helped spread grape seeds.
The study of seeds tells the story of the spread, adaptation and extinction of grapes over thousands of years, showcasing their resilience to survive in other parts of the world despite disappearing from Central and South America over time.
Several fossils are related to modern grapes and others are distant relatives or grapes native to the Western Hemisphere. For example, some fossil species can be traced to grapes found today only in Asia and Africa, but it’s unclear why grapes became extinct in Central and South America, Herrera said.
“The new fossil species tell us a tumultuous and complex story,” he said. “We typically think of modern, diverse rainforests as a ‘museum’ model, where all the species accumulate over time. However, our study shows that extinction has been a major force in the evolution of rainforests. We now need to identify what caused these extinctions over the last 60 million years.”
Herrera wants to look for other examples of fossil plants, such as sunflowers, orchids and pineapples, to see if they existed in ancient rainforests.
Studying the origins and adaptations of plants in the past helps scientists understand how they might fare during the climate crisis.
“I just hope that most living plant seeds will quickly adapt to the current climate crisis. Seed fossils tell us that plants are resilient, but they can also completely disappear from an entire continent,” Herrera said.