Hexbyte Glen Cove Early long-distance trade links shaped Siberian dogs, study finds thumbnail

Hexbyte Glen Cove Early long-distance trade links shaped Siberian dogs, study finds

Hexbyte Glen Cove

Nenets dogs of the Siberian Arctic resting beside a dogsled in the Iamal-Nenets region of Siberia. Credit: Robert J. Losey.

Archeological finds show that people in the Arctic regions of Northwestern Siberia had already established long-range trading links with Eurasian populations some 2000 years ago. The initiation of trading relationships was one of a series of significant social changes that took place during this period. Moreover, these changes even had an impact on the genomes of Siberian dogs, as an international team of researchers led by LMU palaeogeneticist Laurent Frantz has now demonstrated. Based on extensive genetic analyses, the team concludes that dogs were imported into the Siberian Arctic, and that this process ultimately led to the establishment of Siberian breeds such as the samoyed.

Genomes dating from the Stone Age to the Holocene

The researchers analyzed the genomes of 49 dogs from sites in Siberia and Eurasia dating to between 60 and about 11,000 years ago. Four of the dogs originated from Ust-Polui, where Russian and Canadian archeologists have uncovered the remains of more than 100 dogs dating back to about 2000 years ago. Numerous finds indicate that this site on the remote Yamal peninsula in Northwestern Siberia was in use—most probably for ceremonial purposes—over a period of about 400 years.

“Some of the dogs found there appear to have been intentionally buried,” says Dr. Robert Losey, from the University of Alberta, and lead archeologist of the study. “But there is also evidence which suggests that many were eaten. Dogs were used for a variety of purposes—not only as a means of transport, but potentially also hunting partners and as sources of food.”

The artifacts uncovered in Ust-Polui include glass beads and objects made of metal, which cannot have been fabricated locally. They must have been sourced from the steppe zone, the Black Sea region or the Near East. Therefore, the people who lived on the Yamal peninsula must have been integrated into long-range trading networks more than 2000 years ago. This was also a time of significant social and technological change—as indicated by the exploitation of iron ore and artifacts related to reindeer harnessing both being evidenced at the site. Large-scale reindeer pastoralism, now widely practiced by Indigenous people in this region, emerged here only in the last few centuries.

Dogs as trade goods

The new genetic analyses revealed that dogs were also among the goods imported into the Siberian Arctic imported from areas further to the south at this time. “Whereas Arctic dogs evolved in isolation prior to at least 7000 years ago, genomic DNA isolated from Siberian dogs dated to between the Iron Age and medieval times shows that there were increasing portions of genetic material derived from dogs from the Eurasian steppes, as well as Europe,” says Dr. Tatiana Feuerborn, the lead author on the paper based at the University of Copenhagen. Thus, the proportion of non-Siberian ancestry among dogs on the Yamal peninsula increased significantly during this period. “Dogs were potentially valuable possessions, and they were bought and sold,” says Frantz. On the other hand, human genomes in Arctic Siberia remained quite stable over this long stretch of time, and there is little sign of genetic input from non-Arctic populations.

The authors of the new study assume that the import of dogs from farther afield is a reflection of societal transitions in Siberia. “The first dogs domesticated in the Arctic served primarily as sledding dogs,” says Frantz. “When Siberian populations turned to pastoralism, they may well have required dogs that had other useful behavioral traits, which were better suited for reindeer herding. The mixing of Arctic dogs with other populations potentially led to the establishment of dog lineages that were both suited to herding and also adapted to the harsh climatic conditions.”

From working dog to samoyed

This strategy of cross-breeding and selection for improved traits eventually led to the emergence of modern Siberian canine lineages such as the samoyed. “A large fraction of the samoyed genome can be traced back to ancestral Arctic bloodlines,” says Frantz, “but it also shows far more Western influence than the husky, for instance.” Because very little subsequent hybridization with other breeds has occurred in the meantime, yet samoyeds have remained largely unchanged since the Middle Ages. In contrast, most other modern breeds result from the targeted efforts of breeders during the 19th and 20th centuries. Only when polar explorers such as Ernest Shackleton obtained dogs from the Arctic and began to breed from them did the samoyed acquire its modern name. “Prior to that they were simply a population of working ,” says Frantz.

The study is published in the Proceedings of the National Academy of Sciences.



More information:
Modern Siberian dog ancestry was shaped by several thousand years of Eurasian-wide trade and human dispersal, Proceedings of the National Academy of Sciences, 2021. www.pnas.org/cgi/doi/10.1073/pnas.2100338118

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Hexbyte Glen Cove Early land plants evolved from freshwater algae, fossils reveal thumbnail

Hexbyte Glen Cove Early land plants evolved from freshwater algae, fossils reveal

Hexbyte Glen Cove

A new assemblage of fossil spores of Lower Ordovician age, about 480 Ma, are intermediate in character between controversial Cambrian forms and well-accepted plant spores from later Ordovician and Silurian deposits. This linkage aligns fossil spores with molecular data and helps explain why megafossil plants axes don’t appear in the geological record until 75 million years later during the Silurian. Credit: Paul Strother

The world may need to start thinking differently about plants, according to a new report in the journal Science by researchers who took a fresh look at spore-like microfossils with characteristics that challenge our conventional understanding about the evolution of land plants.

Found in rock samples retrieved in Australia more than 60 years ago, the microfossils dating to the Lower Ordovician Period, approximately 480 million years ago, fill an approximately 25-million-year gap in knowledge by reconciling the molecular clock—or pace of evolution—with the fossil spore record—the physical evidence of early plant life gathered by scientists over the years.

This reconciliation supports an evolutionary-developmental model connecting plant origins to freshwater green algae, or charophyte algae, said Boston College paleobotanist Paul Strother, a co-author of the new report. The “evo-devo” model posits a more nuanced understanding of plant evolution over time, from simple cell division to initial embryonic stages, rather than large jumps from one species to another.

“We found a mix of fossils linking older, more problematic spore-like microfossils with younger spores that are clearly derived from ,” said Strother. “This helps to bring the fossil spore record into alignment with molecular clock dates if we consider the of land plants as a long-term process involving the evolution of embryonic development.”

The fossil record preserves direct evidence of the evolutionary assembly of the plant regulatory and developmental genome, Strother added. This process starts with the evolution of the plant spore and leads to the origin of plant tissues, organs, and eventually macroscopic, complete plants—perhaps somewhat akin to mosses living today.

“When we consider spores as an important component of the evolution of land plants, there is no longer a gap in the fossil record between molecular dating and fossil recovery,” Strother said. Absent that gap, “we have a much clearer picture of a whole new evolutionary step: from simple cellularity to complex multicellularity.”

As a result, researchers and the public may need to re-think how they view the origin of terrestrial plants—that pivotal advance of life from water to land, said Strother.

A new assemblage of fossil spores of Lower Ordovician age, about 480 Ma, are intermediate in character between controversial Cambrian forms and well-accepted plant spores from later Ordovician and Silurian deposits. This linkage aligns fossil spores with molecular data and helps explain why megafossil plants axes don’t appear in the geological record until 75 million years later during the Silurian. Credit: Paul Strother

“We need to move away from thinking of the origin of land plants as a singularity in time, and instead integrate the fossil record into an evo-devo model of genome assembly across millions of years during the Paleozoic Era—specifically between the Cambrian and Devonian divisions within that era,” Strother said. “This requires serious re-interpretation of problematic fossils that have previously been interpreted as fungi, not plants.”

Strother and co-author Clinton Foster, of the Australian National University, set out to simply describe an assemblage of spore-like microfossils from a deposit dating to the Early Ordovician age—approximately 480 million years ago. This material fills in a gap of approximately 25 million years in the fossil spore record, linking well-accepted younger plant spores to older more problematic forms, said Strother.

Strother and Foster examined populations of fossil spores extracted from a rock core drilled in 1958 in northern Western Australia. These microfossils are composed of highly resistant organic compounds in their cell walls that can structurally survive burial and lithification. They were studied at Boston College, and at the ANU’s Research School of Earth Sciences, with standard optical light microscopy.

“We use fossil spores extracted from rock drill cores to construct an evolutionary history of plants going back in time to the very origin of plants from their algal ancestors,” said Strother. “We have independent age control on these rock samples, so we study evolution by looking at changes in the kinds of spores that occur over time.”

Molecular biologists also look at evolutionary history through time by using genes from living plants to estimate the timing of plant origins using “molecular clocks”—a measurement of evolutionary divergence based on the average rate during which mutations accumulate in a species’ genome.

However, there are huge discrepancies, up to tens of millions of years, between direct fossil data and dates, said Strother. In addition, there are similar time gaps between the oldest spores and when actual whole plants first occur.

These gaps resulted in hypotheses about a “missing fossil record” of the earliest land ,” said Strother.

“Our work seeks to resolve some of these questions by integrating the fossil spore record into an evolutionary developmental model of plant origins from algal ancestors,” Strother said.



More information:
A fossil record of land plant origins from charophyte algae, Science (2021). science.sciencemag.org/lookup/ … 1126/science.abj2927

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Early land plants evolved from freshwater algae, fossils reveal (2021, August 12)
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