All Species Evolved From Single Cell, Study Finds

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    • #487698
      eridani
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      https://www.nationalgeographic.com/adventure/article/100513-science-evolution-darwin-single-ancestor

      Using computer models and statistical methods, biochemist Douglas Theobald calculated the odds that all species from the three main groups, or “domains,” of life evolved from a common ancestor—versus, say, descending from several different life-forms or arising in their present form, Adam and Eve style.

      The domains are bacteria, bacteria-like microbes called Archaea, and eukaryotes, the group that includes plants and other multicellular species, such as humans. The “best competing multiple ancestry hypothesis” has one species giving rise to bacteria and one giving rise to Archaea and eukaryotes, said Theobald, a biochemist at Brandeis University in Waltham, Massachusetts.

      All species in all three domains share 23 universal proteins, though the proteins’ DNA sequences—instructions written in the As, Cs, Gs, and Ts of DNA bases—differ slightly among the three domains (quick genetics overview). The 23 universal proteins perform fundamental cellular activities, such as DNA replication and the translation of DNA into proteins, and are crucial to the survival of all known life-forms—from the smallest microbes to blue whales.

      A universal common ancestor is generally assumed to be the reason the 23 proteins are as similar as they are, Theobald said. That’s because, if the original protein set was the same for all creatures, a relatively small number of mutations would have been needed to arrive at the modern proteins, he said. If life arose from multiple species—each with a different set of proteins—many more mutations would have been required.

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    • #487873
      Two way street
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      which may be lethal to the organism. Down Syndrome caused by trisomy in human chromosome 21, does lead to a shortened life span, not death to the human.

      https://pubmed.ncbi.nlm.nih.gov/27914620/
      Three repeating alleles is usually lethal also. The other parent will have one or two alleles on its side of the 23 pairs (46 chromosomes).

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