How has DNA evidence confirmed and extended Darwin’s ideas about common descent?

1. DNA sequences lay out the family tree Darwin imagined

Comparative sequence analysis shows that organisms judged close by anatomy or fossils also have closer DNA sequences, producing phylogenetic trees that recapitulate and refine Darwin’s branching pattern of life—exactly the pattern predicted if species descend from common ancestors ^{[1] [4]}. Multiple independent sequence datasets (mitochondrial genes, ribosomal RNA, protein-coding loci) produce congruent trees, strengthening the inference that similarity reflects shared ancestry rather than coincidence ^[5].

2. Universality of the genetic code and shared molecular machinery strengthen the claim

The near‑universality of DNA as genetic material, the conserved genetic code, and the shared core of replication and translation proteins across Bacteria, Archaea and Eukarya point to a single deep ancestry for cellular life—evidence that was unavailable to Darwin but now powerfully supports the last universal common ancestor concept ^{[6] [3]}. That these fundamental molecular systems are largely identical across life makes convergent explanations implausible for the pattern as a whole ^{[2] [7]}.

3. Genetic “detritus” — pseudogenes and nonfunctional remnants — act as historical markers

Regions of DNA that are orthologous but nonfunctional in some lineages—pseudogenes and other genomic relics—accumulate mutations predictably and map onto species relationships in the way expected under descent with modification; these shared genetic errors function like fossils in the genome and provide independent corroboration of common descent ^{[1] [8]}.

4. Statistical tests and comparative genomics have formalized Darwin’s idea

Modern comparative genomics and statistical approaches have moved the hypothesis from plausible to rigorously tested: analyses that compare conserved gene sets across life, and formal information‑theoretic tests of universal common ancestry, overwhelmingly favor common descent over chance or widespread independent origins ^{[6] [9]}. That said, methodological debates remain about how to best model deep-time sequence evolution, and some authors note limits to proving a single origin in absolute terms ^[6].

5. DNA reveals mechanisms that extend Darwin’s original account

Molecular data illuminate processes Darwin could only speculate about: gene duplication followed by divergence explains how new biochemical functions evolve while preserving old ones, and conserved regulatory and protein-interaction subunits show how complexity can increase by accretion and tinkering at the molecular level—mechanisms that map directly onto Darwin’s broader theory but give it mechanistic depth ^{[3] [10]}.

6. Limits, alternative explanations, and open questions

Although DNA evidence is overwhelmingly consistent with common descent, scientists acknowledge conceptual limits: proving a single origin billions of years ago becomes harder the further back one goes, and some universal features might reflect chemical constraints as well as ancestry—meaning aspects of similarity could, in principle, stem from physics/chemistry rather than genealogy ^{[7] [6]}. Researchers therefore treat the molecular case as extraordinarily strong but continue to refine models and probe early stages of life ^[9].

Conclusion

Where Darwin supplied the pattern and a persuasive process, DNA provides the ledger and operational mechanisms: sequence similarities, conserved biochemical systems, shared genomic relics, and formal statistical tests together confirm and greatly extend the hypothesis of common descent by making it quantitative, testable, and mechanistic—while leaving focused scientific questions about the very earliest events in life’s history for active research ^{[1] [2] [6]}.