The fact that all life uses the same basic building blocks is precisely what makes the food web possible! These universally shared similarities might indicate the design of the ecosystem, not common ancestry. Moreover, because all life-forms use DNA (which contains nucleotides) and proteins (made of amino acids), we are able to gain nutrients we need - amino acids and nucleotide bases - from the plants, animals, and other organisms that we eat.
So, there are good functional reasons why all life should use these same molecules. Last year Emily Reeves explained that many properties of the amino acids used in life appear optimal for our biochemical needs. The video argues that this universal similarity across life “hints at a common ancestry.” True, universal common ancestry is one possible explanation for such biochemical similarities - but are there others that go unmentioned by Khan? As we saw with homology in vertebrate limbs, it’s key to appreciate functional requirements. It is of course true that all life uses DNA and proteins. Khan claims that “How the DNA gets replicated and translated and transcribed is very similar from one life-form to another.” Yet a 2020 paper noted that the “Origin of DNA replication is an enigma because the replicative DNA polymerases (DNAPs) are not homologous among the three domains of life, Bacteria, Archaea, and Eukarya.” These differences are so great that one paper asked “ Did DNA replication evolve twice independently?” The paper proposes that “the modern-type system for double-stranded DNA replication likely evolved independently in the bacterial and archaeal / eukaryotic lineages.” And while we’re discussing fundamental biomolecular similarities, another paper compared the genomes of 1,000 different prokaryotic organisms and found that “of the 1,000 genomes available, not a single protein is conserved across all genomes.” That’s why I have devoted four posts to analyzing the outdated junk science in their video on “ Evidence for Evolution.” After going through supposed lines of evidence from embryos, homology, and fossil horses, the video ends by looking at biochemical similarities between organisms, presented as a suite of arguments for common ancestry. With its generally high-quality online content, Khan Academy exercises a remarkable influence on what students and teachers alike learn about science and other subjects.
0 kommentar(er)
