Don’t forget the moment scientists made a chicken grow ‘dinosaur feet’

Don’t forget the moment scientists made a chicken grow ‘dinosaur feet’

Until recently, one of the biggest myths in science was that all dinosaurs had become extinct for the past 65 million years. But thanks to new fossil discoveries that completed our knowledge of avian dinosaurs, we now know that only Some Dinosaurs became extinct after an asteroid collided with Earth; others survived and gave rise to the birds we live with today.

To find out how this evolution happened, researchers in Chile carried out a strange but fascinating experiment in 2016. They manipulated the genes of normal chickens, causing them to develop dinosaur-like tubular fibulae on the underside of their legs, one of two long, spine-shaped bones you’ll find in a drumstick.

In avian dinosaurs like Archeopteryx, the fibula was a tube-shaped bone that reached down to the ankle. Another bone, the tibia, grew to a similar length next to it.

As evolution progressed to a group of avian dinosaurs known as pygostilians, the fibula became shorter than the tibia and sharper and more splintered towards the end, and no longer reached the ankle.

While modern bird embryos still show signs of long, dinosaur-like fibula development, as they grow older, these bones become shorter, thinner, and also take on the splinter-shaped ends of Pigostylian bones, and they never go far enough up the leg to connect with the ankle.

The researchers, led by João Francisco Botelho from the University of Chile, decided to investigate how this transition from a long, tubular fibula occurred in dinosaurs to a short splinter-shaped fibula in birds.

They did this by inhibiting the expression of a gene called IHH or Indian Hedgehog (seriously), which saw their chickens continue to grow the long, dinosaur-like fibulae that originated in their embryonic form.

In doing so, the team discovered something strange. Regular bone development sees cell division and therefore growth stops on the shaft long before the ends stop growing, but in modern chickens fibula growth stops first at the ends.

This means that the fibulae of modern chickens are actively blocked from reaching the length of the bones of their ancient relatives.

molecular-exp(Botelho et al., Evolution, 2016)

Publish your observations in the magazine. Evolution In February 2016, researchers suggested that early maturation of the lower end of the fibula in modern chickens is caused by a bone in the ankle, called the calcaneus.

“Unlike other animals, the calcaneus in bird embryos presses against the lower end of the fibula,” the team explained in a press release at the time. “They are so close that some researchers have even mistaken them for a single element.”

The team suggested that in normal chickens, interactions between the calcaneus and the end of the fibula result in signals similar to those that cause the bone axis to stop growing, preventing the fibula from reaching anywhere near the ankle bone.

But when the Indian Hedgehog gene was turned off, the calcaneus strongly expressed the gene for parathyroid-related protein (PthrP), which allows growth at the ends of bones. This caused their chickens to grow long fibulae that connected to the ankle, just as they would in the Archeopteryx.

“Experimental down-regulation of IHH signaling at a postmorphogenetic stage led to a tibia and fibula of equal length,” the team wrote in the report. “The fibula is longer than in the controls and is fused with the fibula, while the tibia is shorter and bent.”

Unfortunately, the ‘chicken dinosaurs’ did not reach the hatching stage, but the goal of the research was not to breed them to adulthood, but to discover the biological processes that led to the transition from dinosaur legs to chicken legs. modern birds. .

“The experiments focus on unique traits to test specific hypotheses,” explained one of the team, Alexander Vargas. “We not only know a lot about the development of birds, but also about the dinosaur-bird transition, which is well documented by the fossil record. This naturally leads to hypotheses about the evolution of development, which can be explored in the laboratory.”

This is not the first time that dinosaur traits have been “recreated” in modern chickens. In 2015, the same team managed to grow dinosaur feet in their chickens, and a separate team in the US managed to grow a dinosaur-like ‘beak’ in their chicken embryos.

Look below to see how lead researcher and renowned paleontologist Jack Horner managed to do it:

The research was published in Evolution.

A version of this article was first published in March 2016.


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