Did all these stories spring from a common source? To resolve that question, Tehrani took 58 variants of the X-eats-Y tale and classified them based on 72 plot variables: For example, are the protagonists human children or animals? Male or female? What kind of creature plays the villain? Do the protagonists escape, and if so, how?
Next, Tehrani fed that data into three different kinds of algorithms that are used for phylogenetic analysis, a method that biologists commonly use to group together closely related organisms or even genetic signatures and form a “tree of life” diagram. The technique has also been used to trace relationships between different manuscripts, including versions of biblical texts and Chaucer’s “Canterbury Tales.” –Such deep roots you have: How Little Red Riding Hood’s tale evolved – NBC News.com.