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The extinction of dinosaurs may have influenced the creation of an environment that helped the evolution of fruit as we know it today. This, indirectly, will have shaped the evolution of the ancestors of humans (and our desserts).
A study in the January edition of Palaeontology It reinforced the theory about the fundamental role of dinosaurs extinctions in the evolution of fruits.
Os sauropodthe largest terrestrial animals that have ever lived on earth were engineers of ecosystems, deeply modifying their environments by overthrowing trees and eating large volumes of vegetation.
After EXTINCTION OF DINOSAURSthe forests became denser again, preventing the sun from reaching the soil layer, which, many generations later, led to the growth of large seeds and fruits.
Over time, these fruits have become the main source of food for many animal species, including primates ancestors.
The study provides mechanistic evidence in support of this theory that scientists have suspected for a long time, but so far they have not been able to prove through fossil registration.
More than 66 million years ago, when the world still had large and clumsy dinosaurs, the average size of plant seeds was small and the fruits were rare. After its extinction, the seeds and fruits increased exponentially in size.
The investigators hypothesized that this happened because, in denser forests, the competition for light encouraged trees to grow higher and faster than their neighbors, and the trees cultivated from larger seeds had an advantage in this competition .
As an additional benefit, investing in delicious and lush fruits has increased the likelihood that they are ingested and scattered by animals, which helped plants prosper.
However, there were not yet much evidence that supports this theory.
New model supports ancient theory
To resolve the dilemma, the research team created a model in which the size of the seeds and fruits increased in response to the darkest under-blast that followed the extinction of dinosaurs, corresponding to the real trends in seed size in the last 65 million of years.
They have incorporated recently acquired knowledge about how large animals affect the structure of the forest, how seeds develop in seedlings and young trees and how the size of animals has changed over time.
The result: The model closely replied the trends observed in seed and animal size over time.
So far, no surprise. But what happened next, as they continued to perform the model, was a surprise.
The data pointed to a mysterious phenomenon in the fossil record: About 35 million years ago, the seeds reversed their course and started to get smallerbecause land animals have been large enough to have a similar effect to the dinosaurs in forests, though proportionally smaller.
“Our model predicted that these animals would open the forest enough for light to start entering the understory and the larger seeds would no longer be successful about the smallest,” explained the investigation leader Christopher Doughtyda Northern Arizona University.
“Evolutionary pressure for increasing seed size has begun to decrease. We have therefore been able to explain the trends in seed size over time without resorting to external influences, such as climate change, ”he added.
Extinction of the “big guys” 2.0
Another change took place about 50,000 years ago, when another major event of extinction exterminated prehistoric mammals, such as mammoths.
Without these ecosystem engineers, the forest subsques darkened again, and the model predicted long -term increase in seed size in response to the absence of these animals.
Humans, descendants of the first frugivorous primates, were the last to influence the size of the seeds. Where human colonization has led to selective wood extraction practices, light levels in the under-ohes resemble those of the dinosaur forest.
However, if humans fail to play the role of sauropods and are not replaced by other Megafauna engineers, we can expect a darkening of the forest and a subsequent restart of the race to light, with the evolution of larger seeds to regain an advantage over smaller.
