Growing Gills Adult stem cells (ASCs) help keep our bodies…

Growing Gills

Adult stem cells (ASCs) help keep our bodies ticking. These dormant undifferentiated cells are ready at a moment’s notice to generate new specialised cells that can replace old or damaged ones. ASCs also multiply to enable some vertebrates like fish to continue growing, even in adulthood. How can ASCs carry out two separate functions in parallel? To answer this, scientists studied the gills of medaka fish. Gills (one from a genetically-manipulated fish shown here in blue and green) operate many vital functions and their exposure to the elements means their different specialised cells need regular replacing. The team found that ASC function was determined by their positioning in fish gills. However, if the part of the gill containing growth ASCs was lost, homeostatic ASCs could take over and generate new growth ones. In future, understanding how flexible ASCs are in different species could help us identify new ways to use these types of cells in regenerative medicine.

Written by Gaëlle Coullon

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Murder in the Paleolithic? Evidence of violence behind human skull remains

New analysis of the fossilized skull of an Upper Paleolithic man suggests that he died a violent death, according to a study published in the open-access journal PLOS ONE by an international team from Greece, Romania and Germany led by the Eberhard Karls Universität Tübingen, Germany

Murder in the Paleolithic? Evidence of violence behind human skull remains
Right lateral view of the Cioclovina calvaria exhibiting a large depressed fracture
[Credit: Kranoti et al, 2019]

The fossilized skull of a Paleolithic adult man, known as the Cioclovina calvaria, was originally uncovered in a cave in South Transylvania and is thought to be around 33,000 years old. Since its discovery, this fossil has been extensively studied. Here, the authors reassessed trauma on the skull—specifically a large fracture on the right aspect of the cranium which has been disputed in the past—in order to evaluate whether this specific fracture occurred at the time of death or as a postmortem event.
The authors conducted experimental trauma simulations using twelve synthetic bone spheres, testing scenarios such as falls from various heights as well as single or double blows from rocks or bats. Along with these simulations, the authors inspected the fossil both visually and virtually using computed tomography technology.

Murder in the Paleolithic? Evidence of violence behind human skull remains
Mechanism of blunt force trauma on the vault A) Low velocity impact on the skull causing fracture formation
at the impact point due to initial inbending of the cranial vault with peripheral outbending; inward displacement
of the bony fragment due to plastic deformation; small fragments remaining in place suggest that the impact
 took place while soft tissue was present. B) Radiating fractures in the area of outbending which start at one
or more points distant to the impact site, progressing both towards to the impact point and in the opposite
 direction (away from it); C) The radiating fractures stop when they meet the sutures (e.g. R1). D)
Formation of concentric fractures forming perpendicular to the radiating fractures
[Credit: Iakovos Ouranos]

The authors found there were actually two injuries at or near the time of death: a linear fracture at the base of the skull, followed by a depressed fracture on the right side of the cranial vault. The simulations showed that these fractures strongly resemble the pattern of injury resulting from consecutive blows with a bat-like object; the positioning suggests the blow resulting in the depressed fracture came from a face-to-face confrontation, possibly with the bat in the perpetrator’s left hand. The researchers’ analysis indicates that the two injuries were not the result of accidental injury, post-mortem damage, or a fall alone.
While the fractures would have been fatal, only the fossilized skull has been found so it’s possible that bodily injuries leading to death might also have been sustained. Regardless, the authors state that the forensic evidence described in this study points to an intentionally-caused violent death, suggesting that homicide was practiced by early humans during the Upper Paleolithic.

The authors add: «The Upper Paleolithic was a time of increasing cultural complexity and technological sophistication. Our work shows that violent interpersonal behaviour and murder was also part of the behavioural repertoire of these early modern Europeans.»

Source: Public Library of Science [July 03, 2019]

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Ancient DNA sheds light on the origins of the Biblical Philistines

An international team, led by scientists from the Max Planck Institute for the Science of Human History and the Leon Levy Expedition, retrieved and analyzed, for the first time, genome-wide data from people who lived during the Bronze and Iron Age (~3,600-2,800 years ago) in the ancient port city of Ashkelon, one of the core Philistine cities during the Iron Age.

Ancient DNA sheds light on the origins of the Biblical Philistines
Excavation of the Philistine Cemetery at Ashkelon [Credit: Melissa Aja, 
Leon Levy Expedition to Ashkelon]

The team found that a European derived ancestry was introduced in Ashkelon around the time of the Philistines’ estimated arrival, suggesting that ancestors of the Philistines migrated across the Mediterranean, reaching Ashkelon by the early Iron Age.
This European related genetic component was subsequently diluted by the local Levantine gene pool over the succeeding centuries, suggesting intensive admixture between local and foreign populations. These genetic results, published in Science Advances, are a critical step toward understanding the long-disputed origins of the Philistines.

Ancient DNA sheds light on the origins of the Biblical Philistines
A team of foreign archaeologists extract skeletons at the excavation site of the first Philistine cemetery 
ever found in the Mediterranean coastal Israeli city of Ashkelon [Credit: Melissa Aja, 

Leon Levy Expedition to Ashkelon]

The Philistines are famous for their appearance in the Hebrew Bible as the arch-enemies of the Israelites. However, the ancient texts tell little about the Philistine origins other than a later memory that the Philistines came from «Caphtor» (a Bronze Age name for Crete; Amos 9:7).

More than a century ago, Egyptologists proposed that a group called the Peleset in texts of the late twelfth century BCE were the same as the Biblical Philistines. The Egyptians claimed that the Peleset travelled from the «the islands,» attacking what is today Cyprus and the Turkish and Syrian coasts, finally attempting to invade Egypt.

Ancient DNA sheds light on the origins of the Biblical Philistines

Excavation of the Philistine Cemetery at Ashkelon [Credit: Melissa Aja, 

Leon Levy Expedition to Ashkelon]

These hieroglyphic inscriptions were the first indication that the search for the origins of the Philistines should be focused in the late second millennium BCE. From 1985-2016, the Leon Levy Expedition to Ashkelon, a project of the Harvard Semitic Museum, took up the search for the origin of the Philistines at Ashkelon, one of the five «Philistine» cities according to the Hebrew Bible.
Led by its founder, the late Lawrence E. Stager, and then by Daniel M. Master, an author of the study and director of the Leon Levy Expedition to Ashkelon, the team found substantial changes in ways of life during the 12th century BCE which they connected to the arrival of the Philistines. Many scholars, however, argued that these cultural changes were merely the result of trade or a local imitation of foreign styles and not the result of a substantial movement of people.

Ancient DNA sheds light on the origins of the Biblical Philistines
Ancient bones excavated in Israel and analysed in Germany may have cracked the puzzle of the Philistines’ 
provenance and provided for the first time evidence of the biblical people’s European origins
[Credit: Melissa Aja, Leon Levy Expedition to Ashkelon]

This new study represents the culmination of more than thirty years of archaeological work and of genetic research utilizing state of the art technologies, concluding that the advent of the Philistines in the southern Levant involved a movement of people from the west during the Bronze to Iron Age transition.

Genetic discontinuity between the Bronze and Iron Age people of Ashkelon

The researchers successfully recovered genomic data from the remains of 10 individuals who lived in Ashkelon during the Bronze and Iron Age. This data allowed the team to compare the DNA of the Bronze and Iron Age people of Ashkelon to determine how they were related.

Ancient DNA sheds light on the origins of the Biblical Philistines
Photograph of infant burial at the Philistine Cemetery at Ashkelon 
[Credit: Ilan Sztulman, Leon Levy Expedition to Ashkelon]

The researchers found that individuals across all time periods derived most of their ancestry from the local Levantine gene pool, but that individuals who lived in early Iron Age Ashkelon had a European derived ancestral component that was not present in their Bronze Age predecessors.
«This genetic distinction is due to European-related gene flow introduced in Ashkelon during either the end of the Bronze Age or the beginning of the Iron Age. This timing is in accord with estimates of the Philistines arrival to the coast of the Levant, based on archaeological and textual records,» explains Michal Feldman of the Max Planck Institute for the Science of Human History, leading author of the study. «While our modelling suggests a southern European gene pool as a plausible source, future sampling could identify more precisely the populations introducing the European-related component to Ashkelon.»

Transient impact of the «European related» gene flow

In analyzing later Iron Age individuals from Ashkelon, the researchers found that the European related component could no longer be traced. «Within no more than two centuries, this genetic footprint introduced during the early Iron Age is no longer detectable and seems to be diluted by a local Levantine related gene pool,» states Choongwon Jeong of the Max Planck Institute of the Science of Human History, one of the corresponding authors of the study.

«While, according to ancient texts, the people of Ashkelon in the first millennium BCE remained ‘Philistines’ to their neighbors, the distinctiveness of their genetic makeup was no longer clear, perhaps due to intermarriage with Levantine groups around them,» notes Master.

«This data begins to fill a temporal gap in the genetic map of the southern Levant,» explains Johannes Krause of the Max Planck Institute for the Science of Human History, senior author of the study. «At the same time, by the zoomed-in comparative analysis of the Ashkelon genetic time transect, we find that the unique cultural features in the early Iron Age are mirrored by a distinct genetic composition of the early Iron Age people.»

Source: Max Planck Society [July 03, 2019]

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