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We often think the strongest evidence for evolution is fossils and similar DNA across species. That is actually now the WEAKEST evidence for common descent. We have something far more powerful.
Two independent lines of evidence have emerged that make the case for evolution so airtight that fossils and gene similarity are reduced to corroborating details:
Endogenous retroviruses (ERV)and Mitochondrial DNA (mtDNA).
Endogenous retroviruses are the genomic scars left behind when ancient retroviruses infected the germ cells (the cells that become sperm and eggs) of our ancestors and permanently integrated into their DNA. These insertions were then inherited by every descendant of that ancestor. We share hundreds of these identical ERV insertions with chimpanzees at the EXACT same genomic locations. We share fewer with gorillas. Even fewer with orangutans.
But it doesn’t stop there. The same pattern extends across mammals. Cats, dogs, mice, whales. Each sharing ERV insertions with their closest relatives and fewer with more distant ones. Every time the pattern tracks perfectly onto the tree of descent we already know.
To understand why this is so devastating to creationists, consider what an independent insertion would require. A retrovirus would need to infect a germ cell specifically and integrate at an identical genomic location in two completely separate lineages independently.
The probability of this happening even once by chance is effectively zero. A PATERNITY test which courts use to convict compares dozens of STR markers. Shared ERV insertions are a single event so improbable that the paternity test is even LESS robust than this analysis. We don’t have one shared insertion. We have HUNDREDS across dozens of species.
Mitochondrial DNA works as an independent control. It is inherited exclusively through the maternal line, mutates at a known rate, and has no connection to ERV insertions whatsoever. When you build a phylogenetic tree using ONLY mtDNA you end up with the same tree as one built using ONLY ERV. Two completely independent lines of evidence with no reason to converge and they converge perfectly. Across ALL ANIMALS.
Fossils and gene similarity at this point are just nice to haves. If we had never found a single fossil, ERVs and mtDNA alone would prove common descent beyond any reasonable evidentiary standard.
To all my creationists: you probably never knew this argument existed. What do you think? I am genuinely curious.
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