Modern grapes exist because dinosaurs disappeared, new research finds

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Grapes have been intertwined with human history for millennia, 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 Earth 66 million years ago, it destroyed the huge, lumbering animals and set the stage for other creatures and plants to thrive in the aftermath.

Now, the discovery of fossilized grape seeds in Colombia, Panama and Peru, ranging in age from 19 million to 60 million years, is shedding light on how these humble fruits became established 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’s Plants.

“These are the oldest grapes ever found in this part of the world and are a few million years younger than the oldest grapes ever 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 phases of 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 66 million years, roughly around the time the dinosaurs disappeared.

“We always think about animals, dinosaurs, because they were the most affected, but the extinction event also had a huge impact on plants,” said Herrera. “The forest recovered in a way that changed the composition of the plants.”

A difficult search

Herrera’s doctoral advisor, Steven Manchester, who is also senior author on the new study, published a paper on grape fossils found in India. It inspired Herrera to question where other grape seed fossils might exist, such as 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 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 found in South America.

“She looked at me and said, ‘Fabiany, a grape!’ And then I looked at him and thought, ‘Oh my God.’ It was so emotional,” Herrera said.

Although the fossil was tiny, its shape, size and other characteristics helped the pair identify it as a grape seed. And once they returned to the lab, the researchers performed CT scans to study its internal structure and confirm their findings.

They named the newly discovered species Lithouva susmanii, or “Susman’s seed grape,” in honor of Arthur T. Susman, who has supported South American paleobotany at the Field Museum.

“This new species is also important because it supports the South American origin of the group in which the common 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 break 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 the discovery, the team carried out more fieldwork in South and Central America and found nine new species of fossil grape seeds trapped in sedimentary rocks. And by tracing the lineage from ancient seeds to modern grapes, the team realized that something allowed the plants to thrive and spread.

How ancient forests have changed

When dinosaurs went extinct, their absence changed the entire structure of forests, the team surmised.

“Large animals, such as dinosaurs, are known to alter surrounding ecosystems. We think that if there were large dinosaurs roaming the forest, they would probably be cutting down trees, effectively keeping the forests more open than they are today,” said Carvalho.

After the dinosaurs disappeared, rainforests overgrew and layers of trees created an 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 the vines 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.

However, as a diverse set of birds and mammals began to populate the Earth after the dinosaurs disappeared, it is likely that they also helped spread grape seeds.

The resilience of plants

The study of 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 the years. of 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 now 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 typically 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 during 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 respond during the climate crisis.

“I can only 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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