Maximum Parsimony vs Maximum Likelihood Explained
Maximum Parsimony picks the simplest evolutionary tree requiring the fewest genetic changes. Maximum Likelihood calculates the probability of observed data under different trees and chooses the most probable one.
People confuse them because both build trees from DNA, yet one prizes simplicity while the other prizes probability. Think of it as choosing the shortest road trip versus the most reliable route—different priorities, same destination.
Key Differences
Parsimony counts steps: fewer mutations win. Likelihood weighs probabilities: likelier mutations win, even if more numerous. One seeks the minimal story; the other, the most believable story.
Which One Should You Choose?
Use Parsimony when data are limited and you want a quick, clear picture. Choose Likelihood when you have more genetic info and want to account for varying mutation rates.
Examples and Daily Life
Imagine tracing family nicknames: Parsimony assumes the shortest change (John → Jon), while Likelihood considers pronunciation shifts that make John → Jack more probable.
Is Maximum Parsimony always faster?
Generally yes; counting steps is simpler than computing probabilities.
Can I use both methods together?
Yes, many researchers start with Parsimony for speed, then refine with Likelihood.