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Grapes have been intertwined with the human story for millennia, providing the basis for wines made by our ancestors thousands of years ago – but that might not be the case if the dinosaurs hadn’t disappeared from the planet, according to new research.
When an asteroid hit Earth 66 million years ago, it wiped out the massive, lumbering animals and paved the way for other creatures and plants to thrive as a result.
Now, 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 established a global presence. One of the newly discovered seeds is the oldest example of a plant in the grape family 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 several million years younger than the oldest ever found on the other side of the planet,” said study lead author Fabiana Herrera, assistant curator of paleobotany at the Field Museum in Negaunee Integrative Research Center in Chicago, in a statement. “This discovery is important because it shows that after the extinction of the dinosaurs, grapes really began to spread around the world.”
Like the soft tissues of animals, true fetuses do not preserve well in the fossil record. But seeds, which are more likely to fossilize, can help scientists understand what plants were present at different stages of Earth’s history as they reconstruct the tree of life and create origin stories.
The oldest grape seed fossils yet found were discovered in India and date from 66 million years ago, around the time of the extinction of the dinosaurs.
“We always think about the animals, the dinosaurs, because those were the biggest things that could have been affected, but the extinction event had a huge impact on the plants as well,” Herrera said. “The forest reset in a way that changed the composition of the plants.”
Challenging search
Herrera’s doctoral advisor Steven Manchester, who is also the lead author of the new study, published a paper on grape fossils found in India. It inspired Herrera to wonder where other grape seed fossils might exist, such as South America, although they have never been found there.
“Grapes have an extensive fossil record that starts about 50 million years ago, so I wanted to discover one in South America, but it was like looking for a needle in a haystack,” Herrera said. “Even as a student I was looking for the oldest grapes in the Western Hemisphere.”
Herrera and study co-author Mónica Carvalho, associate curator at the University of Michigan Museum of Paleontology, were conducting fieldwork in the Colombian Andes in 2022 when Carvalho spotted the fossil. It turned out to be a 60-million-year-old grape seed fossil trapped in rock, among the oldest in the world and the first found in South America.
“She looked at me and said, ‘Fabian, the grapes!’ And then I looked at it, I was like, “Oh my God.” It was so exciting,” Herrera said.
Although the fossil was tiny, its shape, size and other features helped the pair identify it as a grape seed. And once back in the lab, the researchers performed a CT scan to study its internal structure and confirm their findings.
They named the newly discovered species Lithouva susmanii or “Susman’s stone grape” in honor of Arthur T. Susman, who was a proponent of South American paleobotany at the Field Museum.
“This new species is also important because it supports a South American origin for the group in which the Vitis vine 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 split 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 their find, the team carried out further fieldwork in South and Central America and found nine new species of fossil grape seeds trapped in sedimentary rocks. And by tracing the lineage of ancient seeds to their modern grape counterparts, the team realized that something allowed the plants to thrive and spread.
How the ancient forests changed
When the dinosaurs went extinct, their absence changed the entire structure of the forests, the team hypothesized.
“Large animals like dinosaurs are known to change their surrounding ecosystems. “We think that if there were large dinosaurs running through the forest, they probably would have been cutting down the trees, effectively keeping the forests more open than they are today,” Carvalho said.
After the dinosaurs disappeared, rainforests grew and layers of trees formed the understory and canopy. These dense forests made it difficult for plants to receive light and they had to compete with each other for resources. And creepers had an advantage and used it to reach the canopy, the researchers said.
“In the fossil record, we’re starting to see more plants around this time that use vines to climb trees, like grapes,” Herrera said.
Meanwhile, when a diverse group of birds and mammals began to populate Earth after the dinosaurs disappeared, they probably also helped spread grape seeds.
Plant resistance
The study of the seeds tells the story of how grapes have spread, adapted and become extinct over thousands of years, showing their resilience to survive in other parts of the world, even though they disappeared 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 of the fossil species can be traced to grapes that are found today only in Asia and Africa, but it’s not clear why grapes became extinct in Central and South America, Herrera said.
“The new fossil species tell us a tumultuous and complex history,” he said. “We usually think of diverse and modern rainforests as a model ‘museum’ where all species accumulate over time. However, our study shows that extinction was a major force in the evolution of rainforests. Now we have to find out 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 a climate crisis.
“I just hope that most living plant seeds will quickly adapt to the current climate crisis. The fossil record of seeds tells us that plants are hardy, but they can also disappear completely from an entire continent,” Herrera said.
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