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DNA from mammoth remains reveals the history of the last surviving population

29 June 2024 at 07:15
A dark, snowy vista with a single mammoth walking past the rib cage of another of its kind.

Enlarge / An artist's conception of one of the last mammoths of Wrangel Island. (credit: Beth Zaiken)

A small group of woolly mammoths became trapped on Wrangel Island around 10,000 years ago when rising sea levels separated the island from mainland Siberia. Small, isolated populations of animals lead to inbreeding and genetic defects, and it has long been thought that the Wrangel Island mammoths ultimately succumbed to this problem about 4,000 years ago.

A paper in Cell on Thursday, however, compared 50,000 years of genomes from mainland and isolated Wrangel Island mammoths and found that this was not the case. What the authors of the paper discovered not only challenges our understanding of this isolated group of mammoths and the evolution of small populations, it also has important implications for conservation efforts today.

A severe bottleneck

It’s the culmination of years of genetic sequencing by members of the international team behind this new paper. They studied 21 mammoth genomesβ€”13 of which were newly sequenced by lead author Marianne Dehasque; others had been sequenced years prior by co-authors PatrΓ­cia PečnerovΓ‘, Foteini Kanellidou, and HΓ©loΓ―se Muller. The genomes were obtained from Siberian woolly mammoths (Mammuthus primigenius), both from the mainland and the island before and after it became isolated. The oldest genome was from a female Siberian mammoth who died about 52,300 years ago. The youngest were from Wrangel Island male mammoths who perished right around the time the last of these mammoths died out (one of them died just 4,333 years ago).

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Scales helped reptiles conquer the landβ€”when did they first evolve?

27 June 2024 at 09:40
Multipanel image showing reconstruction of the animal and the prints it left.

Enlarge / Upper left: a reconstruction of Diadcetes. Below: false color images of its foot and tail prints. Right: the section of the tail that left the print. (credit: Voigt et. al./Urweltmuseum GEOSKOP.)

Their feet left copious traces in muddy Permian floodplains, leaving tracks scattered across ancient sediments. But in one slab of such trackways, scientists uncovered something more: the trace of an animal’s tail as it dragged across the ground. Strikingly, these tail prints come complete with scale impressionsβ€”at 300 million years old, they’re among the earliest scale impressions we have.

This may seem small, but it shows us that some of the hardened skin structures necessary for our ancestors to survive on land had evolved much earlier than previously suspected. A paper published in Biology Letters this past May describes this discovery in detail.

A rare find

The particular slab holding these traces was discovered in 2020 at the Piaskowiec Czerwony quarry in Poland. Mining had stopped to enable paleontologists to search the red sandstone rocks for fossils. Gabriela CalΓ‘bkovΓ‘ described climbing upon β€œa huge pile of rubble” only to discover a sizable slab of fossil tracks at the very top. There, among one set of footprints, was something new.

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