Pillar№ 3

Common Descent

All living things are said to share one ancestor, as shown by homology, the tree of life and embryology. Are the similarities evidence of descent, of design, or of both?

Comparative biology · Phylogenetics · Embryology

3.0  In one minute

Living things share deep, nested similarities. That is observed, and it is striking. Reading those similarities as a single family tree is an inference, and the trees built from different genes and traits often disagree.

The reasoning behind each grade is in Explore, one claim card at a time.

ADemonstrated

Shared, nested similarities existObserved across anatomy, development and genomes.

CPlausible inference

Similarity demonstrates common ancestryA plausible inference; common design also predicts similarity.

DExtrapolation

All evidence converges on one treeConflict between trees is pervasive and grows with data.

?  Reasoning at a glance

Where similarity is defined by ancestry, it cannot then be counted as independent evidence of ancestry. Every card in this pillar has to keep the pattern and its explanation apart.

Both common descent and common design predict nested similarity. The evidence that would favour one over the other is the evidence each card asks for.

Diagnosed across this pillar
  • 6 possible
  • 2 clear
  • 1 clear · 1 possible
  • 2 possible
  • 1 possible

Both readings are checked. How it works →

Interactive · Comparative Anatomy ViewerTake apart the arm, the flipper and the wing, and four other biological machinesRotate and explode 3D models of the pentadactyl limb, the vertebrate eye, the bird and lizard lung, ATP synthase and the bacterial flagellum. Remove any part to see what fails, and compare common descent with common design.Open the viewer →