A Hidden Mathematical Rule Is Responsible For The Shape Of Bird And Dinosaur Beaks
Bird beaks come in almost every shape and size, but what determines the form they will take? Just how exactly can they be so different from one another?
According to a new study, a hidden mathematical rule is behind this diversity. It is responsible for the shape and growth of beaks in almost all living birds.
By using this mathematical rule to study beaks, scientists can begin to learn more about the evolution of the faces of birds and other dinosaurs over the course of 200 million years.
It is rare to find rules in biology that apply across all species. But when a rule is found, it can help to detect patterns in nature.
The simple mathematical rule explains the shape and growth of pointed structures like horns, teeth, hooves, shells, and beaks.
It captures how the width of a pointed structure expands from the tip to the base. This rule is called the “power cascade.”
Most dinosaurs had pointed teeth and a robust snout, but others did not have teeth at all. Instead, they had beaks.
In theropods, beaks evolved at least six times, and each time, the teeth were lost. Over millions of years, the snout stretched into a beak shape.
Only one of these dinosaur groups survived the mass extinction event 66 million years ago and eventually became our modern-day birds.
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The research team examined 127 species of theropods to investigate the power cascade rule of growth. They found that 95 percent of theropod beaks and snouts follow the rule.
After the birds survived the mass extinction, they went through a period of major change. Birds now live all over the world and have unique beaks that are specifically adapted to their own environments.
There are beak shapes geared toward eating fruit, catching insects, sipping nectar, and tearing through meat.
Most of them follow the power cascade growth rule, but a rare few were the exceptions. One of the rule-breakers is the Eurasian spoonbill, which has a beak shape that helps it sift through mud to scoop up aquatic life. Its beak resembles a spatula, which is how the bird got its name. Its distinctive feeding style may have led to it breaking the rule.
Overall, the majority of bird and dinosaur beaks follow the power cascade except for the occasional oddball like the spoonbill. The spoonbill emphasizes just how informative the power cascade rule is.
Moving forward, researchers hope to study how bird beaks grow from chick to adult. If the power cascade really is a foundational rule in the growth of bird beaks, perhaps it can be found in other forms as well.
The details of the latest findings were published in the journal iScience.
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