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Thread: "...only 1.5 to 7% of the modern human genome is uniquely human"

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    "...only 1.5 to 7% of the modern human genome is uniquely human"

    An ancestral recombination graph of human, Neanderthal, and Denisovan genomes

    Many humans carry genes from Neanderthals, a legacy of past admixture. Existing methods detect this archaic hominin ancestry within human genomes using patterns of linkage disequilibrium or direct comparison to Neanderthal genomes. Each of these methods is limited in sensitivity and scalability. We describe a new ancestral recombination graph inference algorithm that scales to large genome-wide datasets and demonstrate its accuracy on real and simulated data. We then generate a genome-wide ancestral recombination graph including human and archaic hominin genomes. From this, we generate a map within human genomes of archaic ancestry and of genomic regions not shared with archaic hominins either by admixture or incomplete lineage sorting. We find that only 1.5 to 7% of the modern human genome is uniquely human. We also find evidence of multiple bursts of adaptive changes specific to modern humans within the past 600,000 years involving genes related to brain development and function.

    https://advances.sciencemag.org/cont...medium=Twitter

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    Neanderthals and also Denivsovans are clustering with today's Sub Saharan Africans in PCAs. When you compare their SNPs for hair, eye, skin color, their facial appearance genetics, they also do not resemble much any so called “Out of Africa” population, but today's Africans. There are even more genetic traits of Neanderthals that match today's Sub Saharan African populations, physiological and psychological in their SNPs.

    It seems more likely that Africa was populated by Neanderthal-like peoples who replaced the African Hominids(Or who ever lived there) to survive the glaciation Periods. The Idea of Basal Eurasian as a core population for modern Eurasians would be obsolete in this scenario.
    Another thing supporting this is that Africa is the only continent where Megafauna (Which is believed to be connected to Neanderthal survival) continued to exist.

    Some people suggested the high African components of Neanderthals in PCAs are attributed to lacking differentiation of calculators, but why then other human samples of the same time period (40.000) do get raibow-like Eurasian admixture and not African?

    To support the whole Basal Eurasian/out of Africa Idea we would need ancient African samples from 45.000+ but not a single one is available.
    It is also not so easy to get this data, because the countries where those samples could be collected sometimes don't want this, see Hofmeyr Skull controversy.

    So one could argue that modern humans directly descended from Neanderthals (Or their ancestral population) in Eurasia and so called Neanderthal admixture is nothing more then decreasing atavism and not an mixing event somewhere in the Levant or Arabian peninsular.

    Another thing pointing to this is the mtdna and Y-dna:

    Eurasians

    GoyetQ11633.000
    Y:C1a
    mt:M

    Individual from the new Study (PRJEB41420
    )Caucasus 25.000
    mt:H2a2a1

    Gravettian Krems 29.000
    Y:I
    mt:U5

    Oase 40.000
    Y:F
    mt:N

    Peștera Muierii 40.000
    mt:U6

    Salkhit 33.000
    mt:N

    Ust Ishim 43.000
    Y:K
    mt:R

    Sunghir 33.000
    Y:C1a2
    mt:U8c U2

    Zlaty Kun 45.000
    mt:A2f2

    Neanderthals

    Devils Tower
    mt:M7c1d

    Forbes Quarry
    Y:BT
    mt:R0

    Mezmaiskaya
    Y:B2b1
    mt:L4b2a2a

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    Just a curiosity about evolution of species.

    If admins feel this post is not relevant for this thread, please feel free to delete it or move it to a more suitable topic.

    An exteme example of interspecies deep convergence:

    Ichthyosaurs are extinct marine reptiles that, like dolphins, have terrestrial ancestors. In both groups, adaptation to oceanic life led to the evolution of a hydrodynamic body, with a short neck and modified legs into fins. The comparison between dolphins and ichthyosaurs is often used as an example of evolutionary convergence , which is the name given to the process by which similar structures evolve into distant species with similar ways of life.

    Several complete fossils of ichthyosaurs were found in England during the 19th century, fueling Darwinian and anti-Darwinian discussions (Figure 1). In the late 19th century, new fossils found in Holzmaden , southern Germany, showed that the convergence between dolphins and ichthyosaurs was even deeper. These fossils, exceptionally well preserved, preserved, in addition to the skeleton, the silhouettes of the bodies showing the presence of a lobe caudal fin and a dorsal fin, just like a shark or dolphin (in the photo above, a fossil of Stenopterygius, compared to a great white shark). Some of the fossils found at Holzmaden were pregnant females, showing that ichthyosaurs gave birth at sea, and that offspring were born tail first, an adaptation to avoid drowning, just like modern cetaceans.
    Figure 1: Drawing by Sir Henry de la Bèche (1930): “Ichthyosaurs watching a class on fossilized human remains”. Fossils with dorsal fin and lobe tail fin were not yet known and ichthyosaurs were portrayed as aquatic lizards.

    But there was more convergence. Last week, scientists from different countries published the reanalysis of a fossil of Stenopterygius ichthyosaur , an ichthyosaur found in Holzmaden with traces of the skin and dermis . Using modern techniques of chemistry and microscopy, the scientists showed the presence of ***ment cells evenly distributed in the dorsal part of the body, but absent in the belly region, forming a pattern that is common in many modern marine species: dark back and light belly . This pattern, called " counter-shadow " ( countershading), famous in penguins, works as a camouflage when viewed from below against the light of the sky and when viewed from above against the darkness of the sea. It is also thought to aid in the thermoregulation and absorption of ultraviolet rays.
    The analysis also showed that the skin was smooth, without scales, reminiscent of the skin of a leatherback turtle , the largest and most oceanic of modern turtles. Smooth skin decreases resistance, improving hydrodynamic efficiency. Adult dolphins and seals, for example, have virtually no fur.
    The most significant finding, however, was under the skin. Thermal insulation is a critical issue for aquatic animals as heat dissipates more easily in water than in air. Some modern marine mammals, such as otters and sea lions, use a very dense coat as insulation. Hairless species, such as dolphins and seals, use a thick layer of fat around their bodies, called blubber , as an even more efficient thermal insulator. Fat is so abundant that, before industrial oil production, it was the main source of fuel oil used by mankind (Figure 2).
    Underneath the skin of Stenopterygius ichthyosaur , researchers found remnants of tissue similar to blubber . In modern species, the blubber layer is also used as an energy reserve and to increase buoyancy. But its main function is to allow the maintenance of a constant temperature and above the ambient temperature. That is, it allows animals to be homeothermic even in environments as adverse as the polar seas.
    Figure 2: (A) A cutaway seal showing the dense layer of blubber (b) around the abdomen; (B) Blubber traces identified by microscopy using different types of illumination in Stenopterygius ichthyosaur.

    Currently, mammals and birds are the only homothermic vertebrates, having acquired this characteristic independently. The presence of blubber in ichthyosaurs is a strong indication that they were also able to regulate their temperature, as suggested in previous studies that looked at oxygen isotopes. The convergence between ichthyosaurs and dolphins therefore goes beyond body shape and fins. It would also be in the physiology and in the migratory and ecological possibilities that only a homeothermic metabolism allows.
    João Francisco Botelho (PUC de Chile)
    TO KNOW MORE:
    Bernard A, Lécuyer C, Vincent P, Amiot R, Bardet N, Buffetaut E, et al. Regulation of Body Temperature by Some Mesozoic Marine Reptiles . Science. 2010;328(5984):1379-82.
    Lindgren J, Sjövall P, Thiel V, Zheng W, Ito S, Wakamatsu K, et al. Soft-tissue evidence for homeothermy and crypsis in a Jurassic ichthyosaur . Nature. 2018.
    Lingham-Soliar T. Convergence in Thunniform Anatomy in Lamnid Sharks and Jurassic Ichthyosaurs . Integral Comp Biol. 2016;56(6):1323-36
    Opening photo : White shark and Stenopterygius sp. , a fossil from Holzmaden.



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    ^^ Good example, I actually reposted mine in the other thread instead, since I was making the point of Onge there.

    https://www.eupedia.com/forum/thread...l=1#post627529

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