(ORDO NEWS) — A controversial study found that dinosaur brains contained as many neurons as modern primates, and tyrannosaurus rex intelligence may have approached that of baboons.
True, not all experts agree with such bold conclusions.
Assessing the intelligence of an animal, especially an extinct one, is not easy. A good indicator is the encephalization coefficient (EQ) – the ratio of the actual brain mass to the brain mass characteristic of an animal of the appropriate size.
In humans, the EQ reaches 7.8, in a tyrannosaurus rex – 2.4.
However, such indicators do not give accurate estimates of intelligence, because for the “performance” of the brain, not only its size is important, but also its structure: the number of neurons, the area of the cortex, and so on.
And counting the density of neurons shows that some birds are four times more than rodents and twice as many as most primates.
For long-extinct dinosaurs, such work is impossible: in their fossilized remains, individual fragments of the brain are preserved only in unique cases.
On the other hand, the evolutionary relationship between reptiles, birds, and dinosaurs allows some parallels to be drawn.
Such a study was done by Susana Herculano-Houzel of Vanderbilt University.
The scientist relied on existing databases on the neuroanatomy of reptiles and birds, determining the correlation between the mass of the telencephalon – the anterior part, which includes the large hemispheres – and the number of neurons in it.
According to her, the exact ratio depends on the specific group of dinosaurs. For example, the same theropods, according to this indicator, approached modern birds, and herbivorous sauropods – with reptiles.
Further, the size of the brain of dinosaurs can be estimated from the inner surface of their skull, and then calculate the density and number of nerve cells, based on the previously found correlation.
The work showed that the theropod cerebral cortex contained quite a considerable number of neurons.
The six-meter-high Alioramus could have had as many as a billion, which brings them closer to modern capuchin monkeys, while tyrannosaurs have 3.3 billion, slightly more than baboons.
Given that these predators took four to five years to mature and could live up to 50 years, Herculano-Husel believes they could very well be as smart as these primates.
Paleontologists greeted the article with mixed reviews. Most noted the originality and promise of the approach, but at the same time the excessive courage with which the scientist conducts her extrapolations.
In addition, she relied on somewhat outdated data on the size of the brain of dinosaurs: more recent studies estimate their size to be somewhat smaller.
Finally, “extraordinary claims require extraordinary evidence.” And if the first ones are definitely present in the work of Herculano-Husel, then there are still problems with the second ones.
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