Grapes have been intertwined with human history for millennia, providing the basis for the wines produced by our ancestors thousands of years ago, but perhaps that wouldn’t have happened if dinosaurs hadn’t disappeared from the planet, according to new research.
When an asteroid hit Earth 66 million years ago, it wiped out the huge lumbering animals and set the stage for other creatures and plants to thrive later.
Now, the discovery of fossilized grape seeds in Colombia, Panama and Peru, which range from 19 million to 60 million years old, is shedding light on how these humble fruits managed to gain a foothold in Earth’s dense forests and eventually establish a presence global. One of the newly discovered seeds is the oldest example of grape plants 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 found on the other side of the planet,” said study lead author Fabiany Herrera, assistant curator of paleobotany at the Field Museum at Chicago’s Negaunee Integrative Research Center, 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, real fruits do not 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 in Earth’s history as they reconstruct the tree of life and establish origin stories.
The oldest grape seed fossils found so far were discovered in India and date back to 66 million years ago, around the time of the extinction of the dinosaurs.
“We always think about the animals, the dinosaurs, because they were the biggest things to be affected, but the extinction event had a big impact on plants as well,” Herrera said. “The forest reorganized itself in a way that changed the composition of the plants.”
A difficult search
Herrera’s doctoral advisor, Steven Manchester, who is also a co-author of the new study, published a paper on grape fossils found in India. This inspired Herrera to question where other grape seed fossils might exist, such as in South America, even though they had 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,” said Herrera. “I’ve been looking for the oldest grape in the Western Hemisphere since I was an undergraduate.”
Herrera and study co-author Mónica Carvalho, assistant curator at the University of Michigan Museum of Paleontology, were conducting fieldwork in the Colombian Andes in 2022 when she spotted a fossil. It was a 60-million-year-old grape seed fossil trapped in a rock, one of the oldest in the world and the first to be found in South America.
“She looked at me and said, ‘Fabiany, a grape!’ And then I looked at her and thought, ‘Oh my God.’ It was so emotional,” Herrera said.
Although the fossil was small, its shape, size and other characteristics helped the pair identify it as a grape seed. And once back in the lab, the researchers performed CT scans to study its internal structure and confirm their findings.
They named the new species discovered Lithouva susmaniior “Susman’s stone grape,” named after Arthur T. Susman, who has been a supporter 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 environments, Herrera said.
“To search for such tiny seeds, I split every available piece of rock in the field,” he said, adding that the difficult search “is the fun part of my job as a paleobotanist.”
Encouraged by their discovery, the team conducted more fieldwork in South and Central America and found nine new species of fossilized grape seeds trapped in sedimentary rocks. And by tracing the lineage of ancient seeds to their modern counterparts, the team realized that something had allowed the plants to thrive and spread.
How ancient forests have changed
When dinosaurs became extinct, their absence changed the entire structure of forests, according to the hypothesis put forward by the team.
“Large animals, like dinosaurs, are known for altering their surrounding ecosystems. We think that if there were large dinosaurs roaming the forest, they were probably cutting down trees, effectively keeping the forests more open than they are today,” said Carvalho.
After the dinosaurs disappeared, tropical forests became densely populated, and layers of trees created an understory and canopy. These dense forests made it difficult for plants to obtain light, as they had to compete with each other for resources. And climbing plants had an advantage and used it to reach the canopy, the researchers said.
“In the fossil record, we started to see more plants that use vines to climb trees, like grapes, around this time,” Herrera said.
Meanwhile, as a diverse set of birds and mammals began to populate Earth after the dinosaurs disappeared, they likely also helped spread grape seeds.
The resilience of plants
Studying the seeds tells a story about how grapes spread, adapted and became extinct over thousands of years, showing 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 of the fossil species can be traced back to grapes that today are only found 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 often think of modern, diverse tropical forests as a model ‘museum’ where all species accumulate over time. However, our study shows that extinction has been an important force in the evolution of tropical forests. Now we 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 past origins and adaptations of plants is helping scientists understand how they might behave during the climate crisis.
“I just hope that most living plant seeds adapt quickly to the current climate crisis. The fossil record of seeds tells us that plants are resilient, but they can also completely disappear from an entire continent,” said Herrera.
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