Environmental changes are responsible for the diversification of sharks

Origins of carcharhiniform shark diversification

This is the most diverse group of sharks. There are 290 of them, and there are small sharks like the fruit bat as well as large predators like the hammerhead shark or the bulldog shark.

This group also has a long evolutionary history: the oldest fossils date back to 170 million years ago. And we find a lot of them because sharks, ancient or modern, lose their teeth and replace them continuously throughout their lives.

These researchers wanted to understand how a group that was so diverse early in its history became the dominant group of sharks today. To do this, they gathered all the available fossil records… and determined the age of appearance of each species with models. Only, for the last 20-30 million years, there are few traces of present-day species in the fossil record. To avoid this problem, they took a second approach, combining their data with molecular phylogeny, tracing a family tree with DNA sequences.

As a result, very little happens during the first 80 million years of their evolutionary history, we have mostly small fruit bats… Then, the emergence of new species accelerates in the Cretaceous-Tertiary crisis, that of the dinosaurs… and finally, the diversification in the last thirty million years boom is happening… especially under the influence of climate, which has current implications for conservation.

Interview with Guillaume GuinotLecturer and paleontologist at the Institute of Evolutionary Sciences in Montpellier and co-author

to learn

CULTURE MORNINGS – 852 JDS / ITW guillaume guinot

1 min

Scientific method

58 min

Finding a 3,000-year-old crime scene

Discovered in 2008, but who knows

results just printed and deciphered

Journal of Science and Future. That year, a team of archaeologists was working on one of the first Mesopotamian cities: Muhammad Diyabi Tell, located in present-day Syria. This city could shelter 2,000-2,500 inhabitants continuously at the beginning and middle of the 2nd millennium BC.

We see an irregularity on the floor of one of the houses: a circle is drawn in the middle of the paving of pebbles. During the excavation, scientists discover a silo for food storage… and two skeletons, but nothing resembling a burial… The two bodies were discarded, not carefully arranged on their backs or sides as was customary. directly into the hole.

Both people are between 20-30 years old. One was stabbed twice, and the other had no joints in his left hand. According to the authors, it could therefore be a cleverly disguised crime scene.

A vaccine that prevents urinary tract infections

This cystitis is mainly caused by bacteria Escherichia coli… To limit the use of antibiotics, which are sometimes ineffective against these strains,

Researchers from Duke University, USA wanted to create preventive treatment.

To do this, they collected certain proteins present on the surface of these pathogenic bacteria and triggered an immune response… by introducing them not into an injection solution, but into a tablet coated with nanofibers… By placing it under the tongue of mice, the scientists found that the effectiveness of this sublingual vaccine was equivalent to a high dose of oral antibiotics, but render the gut microbiota intact. Results that need to be confirmed in humans.

Scientific publications are becoming less and less “innovative”.

Scientific production is exponential, but increasingly less disruptive… Proves it

A team of researchers from the University of Minnesota. To do this, they developed a disruption index… that characterizes how these papers change and disrupt the citation network… For example, an article that changes the vision of a discipline will disrupt the way we cite articles. of the same field… Obviously we stop quoting outdated old ones and quote this new article…

As a result, from 45 million articles, this index has decreased by almost 92% in five decades… The same observation for patents… and this affects all areas of research. We know that since the 2000s, the research environment has become increasingly competitive… “publish or destroy”, which encourages scientists to publish as regularly as possible or risk not seeing career advancement. Despite this, the authors note that the number of highly disturbing studies remains about the same… and the quality of the publications does not decrease.

LSD, Documentary Series

54 min

We thank Guillaume Guinot for his valuable explanations

To continue

Shark Diversification Study (Nature Scientific Reports)

Petty Crimes Among the Mesopotamians: Discovery of a Masked Crime Scene 3000 Years Ago (Science and the Future)

The study of crime in Mesopotamia (The Ancient Near East today)

For vaccination against urinary tract infections (Science and the Future)

Urinary tract infection vaccine study (Advances in Science)

Disruptive science is in decline – and no one knows why (Nature, English)

Innovation Survey of Scientific Publications and Patents (Nature, English)

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