Links: Volcanic Underworld, First Americans, Billion Year Old 3D Microfossils

Readings over the past few weeks.

1) Taking the First Steps Into a Newly Formed Volcanic Underworld: Maya Wei- Haas describes a fascinating landscape on the Canary Islands in the Atlantic Ocean. Volcanic eruptions and the transport of lava via underground tubes has formed a subterranean world of stacked lava tunnels and caves. Their mapping is ongoing and scientists hope to understand not just the details of volcanism and the hazards it poses, but also how life can colonize such nascent surfaces, powered by nutrients from minerals. As one of the scientists remarks- "lava tubes is a rare chance to watch an evolving ecosystem from time zero".

2) It looks like the 23ky old human footprints at White Sands are solid: What is the earliest securely dated evidence of people in the America's? In 2021, there was a report of human footprints from an ancient lake in New Mexico. Since the footprints themselves could not be dated, seeds of an aquatic plant that were found in the same layer were carbon dated to about 23 thousand  years ago. That result was greeted with caution. The main concern was that the seeds may have taken up much older lake water containing less of the radioactive isotope C14. This may have made the dated material look older than it actually was. 

Now, there has been more work on the geochronology of the site using two more independent lines of dating. The results agree with the previously estimated date of 23 thousand  years. ArcheoThoughts summarizes the dating methodologies. 

3) Discovery of oldest 3D-preserved microorganisms: Before organisms evolved the ability to build hard skeletons, their remains have been preserved as impressions on soft sediment or as chemical degradation products recognizable by a light carbon isotope signal. Stefanie Terp reports on a discovery of 3D preservation of microorganisms from a mine in Ukraine. They are 1.5 billion years old! 

Scanning Electron Microscopy reveals the filamentous structure of these creatures. They are most likely a variety of fungi. Groundwater in the granite environment in which they lived was saturated with aluminum and silica. The microorganisms were covered and entombed in micrometer thin layers of aluminum silicate, perfectly preserving their delicate structure.

Holiday Readings: Ancient Amputations, First Americans, Fossil Molluscs

Wishing my readers a very Happy New Year! I hope these readings will be to your liking.

1) Can ancient amputations tell us about the care systems of our ancestors? Paleoanthropologist John Hawks surveys the fossil record of ancient humans for signs of severed limbs due to trauma or disease. He also presents cases of limb loss in other primates and offers a perspective on what all this can tell us about past social systems. 

"Both humans and nonhuman primates show us that survival and life after extreme injuries happen under varied circumstances. Bioarchaeologists tend to highlight severe injuries, which stand out from the more subtle patterns of osteological signs of disease that can be understood only across large samples of skeletons. But such individual stories rarely yield unambiguous interpretations".

2) Finding the First Americans. Anthropologist Jennifer Raff brings together often conflicting genetic and archaeological data on this ever vexing and complicated question of how the Americas were populated. 

3) Finding Molluscs. This podcast (with transcript) is part of an excellent continuing series of earth science and paleontology podcasts by Mongabay India. In this episode, host Sahana Ghosh talks with paleoecologist Devapriya Chattopadhyay on her research on fossil molluscs. Dr. Chattopadhyay uses these creatures to track ancient environmental conditions and ecology. She also speaks on the urgent need for India to create a national fossil repository and museum which will help preserve our deep history for future generations.

Mass Extinction, Peopling Of America, Tale Of The Horse

 Sharing some interesting items:

1) What was the impact of Deccan Volcanism on the end-Cretaceous mass extinction? Improved dating of the timing of volcanism shows that volcanism spanned the mass extinction. But what changes occurred to marine environments because of the outgassing wasn't well documented. A new study uses the oxygen isotope ratios in foraminifera shells to estimate ocean temperature changes before and after the mass extinction. The finding is that the oceans warmed well before the extinction but cooled back again. The warming event doesn't appear to correlate with marine extinctions. Rather the mass extinction coincides with evidence for a meteorite impact. 

Here is a figure from the paper on the estimated temperature changes collated using a variety of proxies:

Source: On impact and volcanism across the Cretaceous-Paleogene boundary

Joshua Sokol has written a good summary of the paper:

A Rapid End Strikes the Dinosaur Extinction Debate.

2) Anthropological geneticist Jennifer Raff has pieced together the genomic story of the peopling of the American continents in this really insightful article. Do read it!

Genomes Reveal Humanity’s Journey into the Americas.

3) And next, onwards to a bit of Indian history. A very interesting conversation between Live History India editor Mini Menon and author Yashaswini Chandra on Ms. Chandra's new book, The Tale of the Horse: A History of India on Horseback. Fascinating story of the horse trade from Central Asia into India and its assimilation as a war animal and into Indian society. 

The Tale of the Horse (video). 

Peopling Of The Americas- Rapid Settlement And Substantial Lineage Extinction Upon European Contact

Here is the full paper : Ancient mitochondrial DNA provides high-resolution time scale of the peopling of the Americas

The exact timing, route, and process of the initial peopling of the Americas remains uncertain despite much research. Archaeological evidence indicates the presence of humans as far as southern Chile by 14.6 thousand years ago (ka), shortly after the Pleistocene ice sheets blocking access from eastern Beringia began to retreat. Genetic estimates of the timing and route of entry have been constrained by the lack of suitable calibration points and low genetic diversity of Native Americans. We sequenced 92 whole mitochondrial genomes from pre-Columbian South American skeletons dating from 8.6 to 0.5 ka, allowing a detailed, temporally calibrated reconstruction of the peopling of the Americas in a Bayesian coalescent analysis. The data suggest that a small population entered the Americas via a coastal route around 16.0 ka, following previous isolation in eastern Beringia for ~2.4 to 9 thousand years after separation from eastern Siberian populations. Following a rapid movement throughout the Americas, limited gene flow in South America resulted in a marked phylogeographic structure of populations, which persisted through time. All of the ancient mitochondrial lineages detected in this study were absent from modern data sets, suggesting a high extinction rate. To investigate this further, we applied a novel principal components multiple logistic regression test to Bayesian serial coalescent simulations. The analysis supported a scenario in which European colonization caused a substantial loss of pre-Columbian lineages.

Several points of interest come to mind.

a) Separation with Siberian common ancestors took place about 24 thousand years ago, followed by a long period of isolation in Beringia (see Fig.).

The founder lineages then settled the America's quite rapidly beginning around 16 thousand years. Sites in Chile show human habitation by 14 thousand years.

b) The much talked about Clovis culture were not the first Americans.

c) There was a demographic collapse among the Native American populations. Charles Mann's 1491 gives quite a sweeping account of both native and Spanish eye witness accounts of the wiping out of entire tribes and communities due to Old World diseases. This paper backs that up using genetics. A comparison of ancient DNA with present day Native American DNA shows that extensive extinction of mitochondrial lineages took place.  In plain language, entire tribes were wiped out to be replaced  much later by natives migrating from some other place, although the authors caution some of the discontinuity of lineages could be because  modern diversity may have been undersampled.  The data for ancient DNA comes principally from the western coast of South America which had large Native American population centers.   Lowland populations went extinct more. Highland populations were less affected. Perhaps population contact was more in the lowlands and diseases like malaria more prevalent in the warmer climes?