Genomic data provides simple evidence for a single origin of life

One hundred and fifty years ago, Charles Darwin’s on the Origin of Species explained the evolution of species through evolution by natural selection. To date, there is no simple piece of evidence demonstrating this concept across species. Chargaff’s first parity rule states that complementary base pairs are in equal proportion across DNA strands. Chargaff’s second parity rule, inconsistently followed across species, states that the base pairs are in equal proportion within DNA strands [G ≈ C, T ≈ A and (G + A) ≈ (C + T)]. Using genomic libraries, we analyzed the extent to which DNA samples followed Chargaff’s second parity rule. In organelle DNA, nucleotide relationships were heteroskedastic. After classifying organelles into chloroplasts and mitochondria, and then into plant, vertebrate, and invertebrate I and II mitochondria, nucleotide relationships were expressed by linear regression lines. All regression lines based on nuclear and organelle DNA crossed at the same point. This is a simple demonstration of a common ancestor across species.