Evolution resembles not just a tree with diverging branches, but a woven tapestry. Threads of ancestry cross when species exchange genes — for example, bacteria pass drug resistance to each other, and plants crossbreed to produce hybrids. Scientists have learned to untangle this knot: they analyze mutations — random typos in the assembly instructions for an organism (DNA).
Three simple rules for how these typos accumulate create a unique pattern. Just as astronomers determine a star's composition from its light, a method called spectroscopy, biologists see hidden crossings by the degree of disorder in mutations, or entropy. It turns out you can almost always tell a simple branching line from a tangled network.
Mathematically proven: even a single gene exchange millions of years ago leaves an indelible trace in DNA. Similar methods are used by linguists for language family trees and programmers for analyzing complex circuits. Just as physics has the Standard Model of elementary particles, in biology simple models of mutations reveal the history of life written in carbon compounds.
The Jukes–Cantor model (1969) treats any substitution of a letter in DNA as equally likely, like a random typo in a word.
Fantastic chimeras are not fiction: science can already recognize genetic traces of hybrids.