Protoceratops had a less sensitive sense of smell than earlier ceratopsian dinosaurs, showing a clear decline. Could humans be going the same way? Photo: ShutterstockA new study by researchers in China and the United States found that horned dinosaurs saw a decline in their intelligence, hearing and sense of smell as they grew larger over 100 million years.
Scientists say human evolution could follow a similar course if we become too reliant on technology.
Researchers found that the sense of smell in early-diverging ceratopsians was more sensitive than in Protoceratops (a Late Cretaceous dinosaur in Asia) and late-diverging ceratopsids
“Early-diverging ceratopsians had higher hearing frequencies than ceratopsids and non-avian theropods,” they wrote in an article published in the peer-reviewed journal Paleobiology in October.
“The early horned dinosaurs bear relatively large brain volumes, even higher than most extant reptiles.”
The scientists explained that while these functions helped the dinosaurs escape their predators when they were smaller, as they grew larger, they became less useful.
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Ceratopsians, known for their frills and horns, were herbivorous dinosaurs that lived in the Jurassic and Cretaceous periods.
Early ceratopsians walked on two legs and measured one to two metres (3.3 to 6.6 feet) in length. This group includes Psittacosaurus and Yinlong, meaning “hiding dragon” in Chinese. While Yinlong did not have large horns or frills, it had a raised and triangular-shaped skull typical of ceratopsians.
But by the late Cretaceous period, after nearly 100 million years of evolution, ceratopsians walked on four legs and measured up to nine metres (29.5 feet) long. For example, Triceratops evolved to be able to fight Tyrannosaurus rex.
The study brought together researchers from the China University of Geosciences, the Institute of Vertebrate Palaeontology and Paleoanthropology in Beijing, the Nanjing Institute of Geology and Palaeontology and George Washington University. They performed CAT scans to produce images and analyse brain cavities of dinosaur skull fossils, from which they could reconstruct brain sizes.
Study author Han Fenglu, an associate professor at the China University of Geosciences in Wuhan, said ceratopsians developed features such as armour-like coverings to defend themselves against carnivorous dinosaurs and other predators.
“As they grew bigger, the vulnerability of becoming prey decreased. The environment became safer for them than their smaller predecessors who were always alert to threats and relied on speed or agility to escape.”
“When the functions that helped dinosaurs stay vigilant were not used as frequently, they degraded,” he said, adding that the sense of smell and hearing were essential for detecting approaching predators.
Using modern animals as examples, Han said carnivorous predators exhibit a relatively high level of intelligence to help social coordination and hunting, particularly those that live in groups like lions.
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In contrast, herbivores such as bison and zebras may not require as much intelligence, as their survival primarily depends on satisfying their hunger and avoiding predators. The survival odds for most group members during a hunt are high when only one or two animals are targeted, he said.
As for humans, Han said being too reliant on technology might reduce our abilities.
“We can hardly return to living in the jungle or savannah after adapting to modern society. We should consider how to maintain our sharpness in our senses and other capabilities as we evolve,” he said.
“People have become increasingly dependent on technologies with the rise of mechanisation and artificial intelligence. It may be difficult to adapt if we suddenly find ourselves without these tools.”
“These findings of dinosaurs remind us not to become too dependent,” he said. “While dinosaurs had no control over their evolution, humans, with our advanced brains, should be able to manage our behaviours and choices.”