Enlarge (credit: Anton Petrus )

Generation over generation, catch after catch, fishing changes fish evolution. This phenomenon, called fisheries-induced evolution, is well documented, though it impacts the myriad species of fish differently. For the North Sea cod, it has meant that early bloomers thrive, while fish that are slower to mature get taken out of the gene pool. This has meant that the fish population is evolving toward smaller sizes. A recent paper models what it would take to reverse this effect through conservation, and what it would mean economically to do so.

“In general, fishing is one of the main drivers of change in marine ecosystems,” Hanna Schenk, a postdoctoral researcher at the German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig and one of the paper’s authors, told Ars.

Fishing increases mortality rates among fish—particularly large fish, which are caught in higher numbers because they are more likely to stay within fishers’ nets. In turn, this puts selective pressure on a species: fish that mature quicker (but remain smaller) gain an advantage. These smaller, early bloomers then pass on their genes more often, which impacts the whole population over time.

Enlarge / A 3D paleoreconstruction of a sauropod dinosaur has revealed that the hind feet had a soft tissue pad beneath the "heel," cushioning the foot to absorb the animals immense weight. (credit: Andreas Jannel)

Ask people to think of a dinosaur, and they'll likely name Tyrannosaurus Rex , the carnivorous antagonist prominently featured in the Jurassic Park and Jurassic World film franchises. But an equally well-known dinosaur clade are the herbivorous sauropods , which include Brachiosaurus, Diplodocus, Apatosaurus , Argentinosaurus , and Brontosaurus . Australian paleontologists have digitally reconstructed these plant-munching giants to glean insight into how their feet managed to support their enormous weight, according to a new paper published in the journal Science Advances.

"We've finally confirmed a long-suspected idea and we provide, for the first time, biomechanical evidence that a soft tissue pad—particularly in their back feet—would have played a crucial role in reducing locomotor pressures and bone stresses," said co-author Andreas Jannel , who worked on the project while completing doctoral studies at the University of Queensland. "It is mind-blowing to imagine that these giant creatures could have been able to support their own weight on land."

Sauropods (clade name: Sauropoda, or "lizard feet") had long-necked, long-tailed bodies that made them the lengthiest animals to have roamed the Earth. They had thick and powerful hind legs, club-like feet with five toes, and more slender forearms. It's rare to find complete Sauropod fossils, and even those that are mostly complete still lack the heads, tail tips, and limbs. Scientists have nonetheless managed to learn a great deal about them, and digital reconstruction is proving to be a valuable new tool in advancing our knowledge even further.

Enlarge / A mammoth tusk thaws out of the ground in Siberia.

Ancient DNA has revolutionized how we understand human evolution, revealing how populations moved and interacted and introducing us to relatives like the Denisovans, a "ghost lineage" that we wouldn't realize existed if it weren't for discovering their DNA. But humans aren't the only ones who have left DNA behind in their bones, and the same analyses that worked for humans can work for any other group of species.

Today, the mammoths take their turn in the spotlight, helped by what appears to be the oldest DNA ever sequenced. DNA from three ancient molars, one likely to be over a million years old, has revealed that there is a ghost lineage of mammoths that interbred with distant relatives to produce the North American mammoth population.

Dating and the mammoth family tree

Mammoths share something with humans: like us, they started as an African population but spread across much of the planet. Having spread out much earlier, mammoth populations spent enough time separated from each other to form different species. After branching off from elephants, the mammoths first split into what are called southern and steppe species. Later still, adaptations to ice age climates produced the woolly mammoth and its close relative, the North American mammoth, called the Columbian mammoth. All of those species, however, are extinct, and the only living relatives are the elephants.

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