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Grapes have been intertwined in the story of humanity for thousands of years, providing the basis for wines produced by our ancestors thousands of years ago – but that might not have been the case if dinosaurs hadn’t disappeared from the planet, according to new research.
When an asteroid hit the Earth 66 million years ago, it wiped out the giant, lumbering animals and set the stage for other creatures and plants to flourish later.
Now, the discovery of fossilized grape seeds in Colombia, Panama and Peru that are between 19 million and 60 million years old is shedding light on how these humble fruits gained a foothold in the Earth’s dense forests and eventually established global presence. One of the newly discovered seeds is the oldest example of a plant from 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 a few million years younger than the oldest ever found on the other side of the world,” said lead study author Fabiany Herrera, assistant curator of the company. paleobotany at the Chicago Integrated Research Center Negaunee Field Museum, in a statement. “This discovery is important because it shows that grapes began to spread around the world after the extinction of the dinosaurs.”
Like soft animal tissues, actual fruits do not hold up well in the fossil record. But seeds are more likely to fossilize, they help scientists understand the plants that were present at different stages of Earth’s history as they reconstruct the tree of life and establish origin stories.
The oldest grape seed fossils found so far have been discovered in India and date back 66 million years, to around the time of the extinction of the dinosaurs.
“We always think about the animals, the dinosaurs, because they were the most affected, but the extinction event also had a big impact on plants,” Herrera said. “The forest rearranged itself in a way that changed the composition of the plants.”
A difficult search
Herrera’s PhD advisor, Steven Manchester, who is also the senior author of the new study, published a paper about the grape fossils found in India. It prompted Herrera to ask where other grape seed fossils might exist, such as South America, although they were never found there.
“Grapes have an extensive fossil record that started about 50 million years ago, 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 student.”
Herrera and study co-author Mónica Carvalho, 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, among the oldest in the world and the first to be found in South America.
“She looked at me and said, ‘Fabiany, grape!’ 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 duo identify it as a grape seed. And when they were back in the lab, the researchers performed CT scans to study their internal structure and confirm their findings.
They named the newly discovered species Lihouva susmanii, or “Susman’s stone grape,” in honor of Arthur T. Susman, who was 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 where Vitis the common grapevine evolved,” said study co-author Gregory Stull of the National Museum of Natural History.
The rocks were deposited in ancient lakes, rivers and coastal sites, Herrera said.
“To search 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 discovery, the team did more fieldwork across South and Central America and found nine new species of fossil grape seeds trapped within sedimentary rocks. And by tracing the lineage of the ancient seeds to their modern grape counterparts, the team realized that there was something that enabled the plants to thrive and spread.
How 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 roaming through the forest, they probably would have cut down trees, and kept forests more open than they are today,” said Carvalho.
After the dinosaurs disappeared, tropical forests became overgrown, and layers of trees formed an understory and canopy. These dense forests made it difficult for plants to get light, and 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 start seeing more plants that use vines to climb trees, like grapes, around this time,” Herrera said.
Meanwhile, as a diverse array of birds and mammals settled on Earth after the dinosaurs were gone, they likely helped spread grape seeds.
Plant resilience
Studying the seeds tells the story of how grapes spread, adapted and became extinct over thousands of years, showing their resilience to survive in other parts of the world despite their disappearance from Central and South America over time.
Many fossils are associated with modern grapes while 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 only found in Asia and Africa today, but it is not clear why the grapes became extinct in Central and South America, Herrera said.
“The new fossil species tell us a messy and complicated history,” he said. “We tend to think of the diverse and modern rainforest as a ‘museum’ model, where all species gather over time. However, our study shows that extinction was a major force in the evolution of rainforests. Now we have to identify what caused those 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 tropical forests.
By studying the origins and adaptations of plants in the past, it is helping scientists to understand how they can cope during the climate crisis.
“I hope that most living plant seeds will quickly adapt to the current climate crisis. The fossil record of seeds is telling us that plants are resilient but can also completely disappear from an entire continent,” said Herrera.
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