Le sinus préauriculaire
Ces gens qui vivent avec des branchies !
Certaines personnes naissent avec une malformation (bénigne) du premier et deuxième arcs pharyngés qui fait apparaitre un petit trou, le sinus préauriculaire, à l'avant des oreilles.
Ce trou est l'équivalent du spiracle des requins, qui est lui-même la relique évolutive des deux mêmes arcs branchiaux. Chez les poissons à machoîre (nos ancêtres inclus), les arcs qui soutenaient la première et seconde paires de branchies sont en effet devenus la mandibule, et le spiracle représente ce qui reste de leur ouverture extérieure.
Le sinus préauriculaire est donc le témoin direct de notre origine parmi les animaux que nous appelons poisson !
Encore une belle preuve de l'évolution.
En savoir plus: https://www.youtube.com/watch?v=GD3Yft_saZ8
Géologie de la baie d'Hudson
Hudson Bay occupies a large structural basin, known as the Hudson Bay basin, that lies within the Canadian Shield. The collection and interpretation of outcrop, seismic and drill hole data for exploration for oil and gas reservoirs within the Hudson Bay basin found that it is filled by, at most, 2,500 m (8,200 ft) of Ordovician to Devonian limestone, dolomite, evaporites, black shales, and various clastic sedimentary rocks that overlie less than 60 m (200 ft) of Cambrian strata that consist of unfossiliferous quartz sandstones and conglomerates, overlain by sandy and stromatolitic dolomites. In addition, a minor amount of terrestrial fluvial sands and gravels of the Cretaceous period are preserved in the fill of a prominent ring-like depression about 325–650 km (202–404 mi) across created by the dissolution of Silurian evaporites during the Cretaceous period.
From the large quantity of published geologic data that has been collected as the result of hydrocarbon exploration, academic research, and related geological mapping, a detailed history of the Hudson Bay basin has been reconstructed. During the majority of the Cambrian Period, this basin did not exist. Rather, this part of the Canadian Shield area was still topographically high and emergent. It was only during the later part of the Cambrian that the rising sea level of the Sauk marine transgression slowly submerged it. During the Ordovician, this part of the Canadian Shield continued to be submerged by rising sea levels except for a brief middle Ordovician marine regression. Only starting in the Late Ordovician and continuing into the Silurian did the gradual regional subsidence of this part of the Canadian Shield form the Hudson Bay basin. The formation of this basin resulted in the accumulation of black bituminous oil shale and evaporite deposits within its centre, thick basin-margin limestone and dolomite, and the development of extensive reefs that ringed the basin margins that were tectonically uplifted as the basin subsided. During Middle Silurian times, subsidence ceased and this basin was uplifted. It generated an emergent arch, on which reefs grew, that divided the basin into eastern and western sub-basins. During the Devonian Period, this basin filled with terrestrial red beds that interfinger with marine limestone and dolomites. Before deposition was terminated by marine regression, Upper Devonian black bituminous shale accumulated in the south-east of the basin.
The remaining history of the Hudson Bay basin is largely unknown as a major unconformity separates Upper Devonian strata from glacial deposits of the Pleistocene. Except for poorly known terrestrial Cretaceous fluvial sands and gravels that are preserved as the fills of a ring of subsided strata around the centre of this basin, strata representing this period of time are absent from the Hudson Bay basin and the surrounding Canadian Shield.
The Precambrian Shield underlying Hudson Bay and in which Hudson Bay basin formed is composed of two Archean proto-continents, the Western Churchill and Superior cratons. These cratons are separated by a tectonic collage that forms a suture zone between these cratons and the Trans-Hudson Orogen. The Western Churchill and Superior cratons collided at about 1.9–1.8 Ga in the Trans-Hudson orogeny. Because of the irregular shapes of the colliding cratons, this collision trapped between them large fragments of juvenile crust, a sizable microcontinent, and island arc terranes, beneath what is now the centre of modern Hudson Bay as part of the Trans-Hudson Orogen. The Belcher Islands are the eroded surface of the Belcher Fold Belt, which formed as a result of the tectonic compression and folding of sediments that accumulated along the margin of the Superior Craton before its collision with the Western Churchill Craton.
En observant bien la forme de la baie, on peut remarquer que la côte est de la baie d'Hudson comporte un demi-cercle dont le centre est situé au nord des îles Belcher[8]. Bien qu'aucune preuve ne l'étaie, une hypothèse avancée est que cette forme cintrée, nommée Nastapoka, indiquerait la présence de l'un des plus grands cratères d'impact météoritiques du monde avec un diamètre de 456 km et âgé d'environ 2 milliards d'années. Parmi les principaux caps créés par cette formation, on retrouve la pointe Louis-XIV, le cap Dufferin et le cap Henrietta Maria.
(...) La baie est située près du centre d'une anomalie gravimétrique, qui a été cartographiée en détail par la mission GRACE.
Phytosaurs (Gabriel N. U.)
Phytosaurs were a widespread and successful group of semi-aquatic, archosaurian reptiles that thrived during the Late Triassic period, approximately 235 to 201 million years ago. They were globally distributed, with fossils found on every modern continent, and were among the top predators in their ecosystems. Ranging in size from 2 to over 12 meters (6 to 40 feet) in length, they bore a remarkable, and classic, example of convergent evolution with much later animals.
Instead of being related to crocodiles, phytosaurs were a distinct lineage of archosaurs, a group that also includes crocodilians, pterosaurs, and dinosaurs. Their most iconic feature was an elongated, heavily armored skull, with nostrils positioned high on a bony crest in front of their eyes, not at the tip of the snout like a crocodile. This adaptation allowed them to breathe while almost completely submerged, much like a modern hippopotamus or crocodile. Their bodies were protected by rows of bony osteoderms (armor plates) embedded in the skin along their back and tail.
Phytosaurs were formidable carnivores, occupying the aquatic apex predator niche that crocodiles would later fill. Different species had different feeding strategies, reflected in their snout morphology: some, like Mystriosuchus, had long, slender, fish-catching snouts filled with numerous conical teeth, while others, like Nicrosaurus, had robust, deep snouts for grappling with larger terrestrial prey that came to the water's edge. They likely spent most of their time in rivers, lakes, and swamps, ambushing prey from beneath the water's surface. The extinction of the phytosaurs at the end of the Triassic period, likely due to widespread volcanic activity and climate change, opened the ecological door for the rise and diversification of the true crocodilians in the Jurassic, which would come to dominate the same semi-aquatic predatory roles for millions of years to come.
The emergence of genetic variants linked to brain and cognitive traits in human evolution (Ilan Libedinsky)
Human evolution involved major anatomical transformations, including a rapid increase in brain volume over the last 2 million years. Examination of fossil records provides insight into these physical changes but offers limited information on the evolution of brain function and cognition.
A complementary approach integrates genome dating from the Human Genome Dating Project with genome-wide association studies to trace the emergence of genetic variants linked to human traits over 5 million years. We find that genetic variants underlying cortical morphology (~300,000 years, P = 4 × 10-28), fluid intelligence (~500,000 years, P = 1.4 × 10-4), and psychiatric disorders (~475,000 years, P = 5.9 × 10-33) emerged relatively recently in hominin evolution. Among psychiatric phenotypes, variants associated with depression (~24,000 years, P = 1.6 × 10-4) and alcoholism-related traits (~40,000 years, P = 5.2 × 10-12) are the youngest.
Genes with recent evolutionary modifications are involved in intelligence (P = 1.7 × 10-6) and cortical area (P = 3.5 × 10-4) and exhibit elevated expression in language-related areas (P = 7.1 × 10-4), a hallmark of human cognition. Our findings suggest that recently evolved genetic variants shaped the human brain, cognition, and psychiatric traits.
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