Evolution News - Many Human Groups Show Evidence of a Sharp Dip in the Population

Many human genomes shaped by past events that caused sharp dips in the population | Plos Genetics.

Distribution of the oldest founder events dated at different locations of the world using ancient and present-day samples. Smaller sized points with warmer color correspond to more recent founder events.

Credit: Rémi Tournebize and Priya Moorjani (CC-BY 4.0)

In a paper published today in Plos Genetics, the author report finding evidence that many human populations show evidence of founder effects with a small number of founders and a consequent genetic bottleneck with a high level of inbreeding.

YEC/Creationism - Notions in Crisis

A spatiotemporal interpretation of population differentiation in SW Asia and Europe based on our model and the geographic distribution of the genomes.
Colored shaded areas indicate approximate putative distributions of populations at different time points. The letters (A) to (H) indicate the chronological order of events; see main text for a detailed description. Note that warmer periods (Bølling and Allerød interstadials, Holocene) correspond to population range expansions while colder periods (LGM, Older Dryas) are associated with contractions. See also Figure S4 for additional f-statistics analyses supporting alternative connections between the Levant and the Aegean/Greece area.

Source: Zoledziewska M.;Sidore C.;Chiang C.W.K.;Sanna S.;Mulas A.;Steri M.;Busonero F.;Marcus J.H.;Marongiu M., et al. (2022)

Ancient DNA maps ‘dawn of farming’


The flood of evidence that YECism and Creationism are notions (I won't grace them with the scientific term, 'theories') in crisis continues with news that two of the largest assemblages of ancient human genomes have revealed that the origins of European farmers was in Turkey, but that population originated many thousands of years earlier from diverse hunter-gatherer populations in Europe and Asia.

Of course, there is absolutely no evidence that all humans are descended from a single founder couple who lived just a few thousand years ago in the Middle East, as creationism's favourite myths claim.

The advances in recovering high quality genomes from ancient remains would be terrifying creationist cult leaders if they weren't safe in the knowledge that their dupes would never dream of checking facts or reading scientific publications in case they had to admit they could be wrong, so articles in science magazine such as Nature or New Scientist will go unnoticed and ignored.

The evidence in question was published in two open access papers in Cell and BioRxiv a few days ago. These works build on the 2016 findings by Lazaridis, Iosif, et al, who showed that:

…the earliest populations of the Near East derived around half their ancestry from a ‘Basal Eurasian’ lineage that had little if any Neanderthal admixture and that separated from other non-African lineages before their separation from each other. The first farmers of the southern Levant (Israel and Jordan) and Zagros Mountains (Iran) were strongly genetically differentiated, and each descended from local hunter–gatherers. By the time of the Bronze Age, these two populations and Anatolian-related farmers had mixed with each other and with the hunter–gatherers of Europe to greatly reduce genetic differentiation. The impact of the Near Eastern farmers extended beyond the Near East: farmers related to those of Anatolia spread westward into Europe; farmers related to those of the Levant spread southward into East Africa; farmers related to those of Iran spread northward into the Eurasian steppe; and people related to both the early farmers of Iran and to the pastoralists of the Eurasian steppe spread eastward into South Asia.

YECism Refuted Again - 120 Million-year Continuous Record of Early Paleozoic in Yukon, Canada

Ordovician black shales of the Mount Hare Formation, Road River Group (approximately 465 million years old) rise above conglomerates of the Aberdeen Member. The dangerous rapids of Aberdeen Canyon (Nan Zhak Nadhàdlaii), created by the Peel River cutting through the resistant conglomerates, appear at bottom left.

Image credit: Erik Sperling

Longest known continuous record of the Paleozoic discovered in Yukon wilderness

It was probably furthest from their minds but scientists from Stanford University have refuted Young Earth Creationism yet again, as is so often the case when science discovers facts about the geology and/or biology of an ancient Earth.

The problem for YECs is that their beliefs are so at variance with the facts that the facts, when uncovered by science, rarely, if ever support them, and in fact almost invariably refuted them, so all scientists need do is to continue to do what scientists do and discover the facts and, intentionally or not, they refute Creationism.

The case in point is the discovery in the Yukon, Canada, of deposits laid down over a period of some 120 million years of the early Palaeozoic era.

As Jossie Garthwaite, writing in Stanford News, explains:

Hundreds of millions of years ago, in the middle of what would eventually become Canada’s Yukon Territory, an ocean swirled with armored trilobites, clam-like brachiopods and soft, squishy creatures akin to slugs and squid.

It’s unheard of to have that much of Earth’s history in one place. There’s nowhere else in the world that I know of where you can study that long a record of Earth history, where there’s basically no change in things like water depth or basin type.

In order to make comparisons throughout these huge swaths of our history and understand long-term trends, you need a continuous record.

The early animals were still living in a low oxygen world.

There’s a ton of debate about how plants impacted the Earth system. Our results are consistent with a hypothesis that as plants evolved and covered the Earth, they increased nutrients to the ocean, driving oxygenation.

Although more oxygen is really good for a lot of organisms, graptolites lost the low oxygen habitat that was their refuge. Any environmental change is going to have winners and losers. Graptolites might have been the losers.

Erik Sperling, lead author
Geological scientist
Stanford University.

A trove of fossils and rock layers formed on that ancient ocean floor have now been unearthed by an international team of scientists along the banks of the Peel River a few hundred miles south of the Arctic’s Beaufort Sea. The discovery reveals oxygen changes at the seafloor across nearly 120 million years of the early Paleozoic era, a time that fostered the most rapid development and diversification of complex, multi-cellular life in Earth’s history.

“It’s unheard of to have that much of Earth’s history in one place,” said Stanford University geological scientist Erik Sperling, lead author of a July 7 study detailing the team’s findings in Science Advances. Most rock formations from the Paleozoic Era have been broken up by tectonic forces or eroded over time. “There’s nowhere else in the world that I know of where you can study that long a record of Earth history, where there’s basically no change in things like water depth or basin type.”

Oxygen was scarce in the deep water of this and other oceans at the dawn of the Paleozoic, roughly 541 million years ago. It stayed scarce until the Devonian, roughly 405 million years ago, when, in a geological blink – no more than a few million years – oxygen likely rocketed to levels close to those in modern oceans and the diversity of life on Earth exploded. Big, predatory fish appeared. Primitive ferns and conifers marched across continents previously ruled by bacteria and algae. Dragonflies took flight. And all of this after nearly four billion years of Earth’s landscapes being virtually barren.

Scientists have long debated what might have caused the dramatic shift from a low oxygen world to a more oxygenated one that could support a diverse web of animal life. But until now, it has been difficult to pin down the timing of global oxygenation or the long-term, background state of the world’s oceans and atmosphere during the era that witnessed both the so-called Cambrian explosion of life and the first of Earth’s “Big Five” mass extinctions, about 445 million years ago at the end of the Ordovician.

“In order to make comparisons throughout these huge swaths of our history and understand long-term trends, you need a continuous record,” said Sperling, an assistant professor of geological sciences at Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth).

Context for past life

With permission from the Na Cho Nyak Dun and Tetlit Gwitch’in communities in Yukon, Sperling’s team, which included researchers from Dartmouth College and the Yukon Geological Survey, spent three summers at the Peel River site. Arriving by helicopter, the research team hacked through brush with machetes beside Class VI rapids to collect hundreds of fist-sized samples of rock from more than a mile of interbedded layers of shale, chert and lime mudstone.

Back at Sperling’s lab at Stanford, a small army of summer undergraduates and graduate students worked over five summers to help analyze the fossils and chemicals entombed in the rocks. “We spent a lot of time splitting open rocks and looking at graptolite fossils,” Sperling said. Because graptolites evolved a vast array of recognizable body shapes relatively quickly, the pencil-like markings left by the fossils of these colony-dwelling sea creatures give geologists a way to date the rocks in which they’re found.

Once the researchers had finished identifying and dating graptolite fossils, they ground the rocks in a mill, then measured iron, carbon, phosphorous and other elements in the resulting powder to assess the ocean conditions at the time and place where the layers formed. They analyzed 837 new samples from the Peel River site, as well as 106 new samples from other parts of Canada and 178 samples from around the world for comparison.

Winners and losers

The data show low oxygen levels, or anoxia, likely persisted in the world’s oceans for millions of years longer than previously thought – well into the Phanerozoic, when land plants and early animals began to diversify. “The early animals were still living in a low oxygen world,” Sperling said. Contrary to long-held assumptions, the scientists found Paleozoic oceans were also surprisingly free of hydrogen sulfide, a respiratory toxin often found in the anoxic regions of modern oceans.

When oxygen eventually did tick upward in marine environments, it came about just as larger, more complex plant life took off. “There’s a ton of debate about how plants impacted the Earth system,” Sperling said. “Our results are consistent with a hypothesis that as plants evolved and covered the Earth, they increased nutrients to the ocean, driving oxygenation.” In this hypothesis, the influx of nutrients to the sea would have given a boost to primary productivity, a measure of how quickly plants and algae take carbon dioxide and sunlight, turn them into new biomass – and release oxygen in the process.

The change probably killed off graptolites. “Although more oxygen is really good for a lot of organisms, graptolites lost the low oxygen habitat that was their refuge,” Sperling said. “Any environmental change is going to have winners and losers. Graptolites might have been the losers.”

The Peel River study section.
(A) Paleogeographic map of Laurentia (ca. 480 Ma) with the study area depicted in the box [from (30)]. (B) Early Paleozoic paleoenvironmental reconstruction of Yukon, Northwest Territories, and British Columbia [modified after (30))]. The northwestern Laurentian margin was divided into a series of shallow-water carbonate platforms (blue) and deep-water shale basins (gray). The Road River Group was sampled at the Peel River locality in the Richardson trough. (C) The majority of the Road River Group consists of unbioturbated interbedded organic-rich mudstone/shale and lime mudstone with local diagenetic chert replacement. Shown here are Tremadocian dark gray to black shale and lime mudstone of the Mount Hare Formation. Seated geologist is at ~38 m in section J1727 [see (30)) for detailed sedimentological discussion of the Peel River section]. (D) Trace fossils occur sporadically throughout the Road River Group, but the primary interval of extensive, continuous bioturbation occurs in the lower to middle Katian (Upper Ordovician). Bedding plane view of heavily bioturbated Katian strata from 81 to 93 m in J1518; 30-cm-long hammer for scale. MCE, Misty Creek embayment; MRE, Meilleur River embayment.

Photo credit: Erik Sperling, Stanford University.

The research team's findings are published, open access, in Science Advances:

Abstract
The extent to which Paleozoic oceans differed from Neoproterozoic oceans and the causal relationship between biological evolution and changing environmental conditions are heavily debated. Here, we report a nearly continuous record of seafloor redox change from the deep-water upper Cambrian to Middle Devonian Road River Group of Yukon, Canada. Bottom waters were largely anoxic in the Richardson trough during the entirety of Road River Group deposition, while independent evidence from iron speciation and Mo/U ratios show that the biogeochemical nature of anoxia changed through time. Both in Yukon and globally, Ordovician through Early Devonian anoxic waters were broadly ferruginous (nonsulfidic), with a transition toward more euxinic (sulfidic) conditions in the mid–Early Devonian (Pragian), coincident with the early diversification of vascular plants and disappearance of graptolites. This ~80-million-year interval of the Paleozoic characterized by widespread ferruginous bottom waters represents a persistence of Neoproterozoic-like marine redox conditions well into the Phanerozoic.

Sperling, Erik A.; Melchin, Michael J.; Fraser, Tiffani; Stockey, Richard G.; Farrell, Una C.; Bhajan, Liam; Brunoir, Tessa N.; Cole, Devon B.; Gill, Benjamin C.; Lenz, Alfred; Loydell, David K.; Malinowski, Joseph; Miller, Austin J.; Plaza-Torres, Stephanie; Bock, Beatrice; Rooney, Alan D.; Tecklenburg, Sabrina A.; Vogel, Jacqueline M.; Planavsky, Noah J.; Strauss, Justin V.
A long-term record of early to mid-Paleozoic marine redox change
Science Advances 07 Jul 2021: Vol. 7, no. 28, eabf4382 DOI: 10.1126/sciadv.abf4382

In stark contrast to YECism, which this research refutes in just about every respect; it confirms very much of what science had deduced about this time in Earth's history, how oxygen levels changed over the period and what impact this had on living organisms and the evolution of the major orders. The interesting thing is how well the recorded change in atmospheric oxygen maps onto the fossil record, showing a very strong causal link between those environmental changes and evolution/extinctions.

This tendency of science to validate its hypotheses with several different strands of evidence is of course to be expected, since these major events are often causally linked. Evolution, for example, is driven largely by environmental change and environmental change is driven by geological and biological change.

YECism, on the other hand only has the camp-fire tales of nomadic hunter-gatherers and simple goat-herders with what little science they had in the fearful infancy of our species, when 'magic' seemed like a sensible explanation for the unknown. The astonishing thing is that this backward superstition still survives today in the face of the considerable body of verifiable scientific evidence, such as this paper, that it is wrong. It really is time that YECs accepted that the Bible is best read as an account of what primitive people used to imagine before they knew any better. They did their best but had no evidence, so used best guesses - and got it badly wrong, as we are now discovering.