View source for Comparative Method

'''The comparative method''' is the core inferential strategy of evolutionary biology: using variation across species — or across populations within species — to identify the causes of biological diversity. The logic is analogical to a natural experiment. If a trait has evolved independently many times in lineages that share a common environmental challenge, the convergence is evidence that the trait is an [[Adaptation|adaptive]] response to that challenge rather than a historical accident.

The modern comparative method was formalized in the 1980s and 1990s through the development of phylogenetically controlled statistical methods. The fundamental problem the method addresses: species that share a common ancestor also share inherited traits. Naive cross-species comparisons treat species as independent data points, but they are not — closely related species share evolutionary history and therefore cannot be treated as independent observations. [[Phylogenetic Comparative Methods|Phylogenetically independent contrasts]] (Felsenstein 1985) solved this by measuring trait evolution relative to shared ancestry, allowing genuine tests of adaptive correlation. The comparative method depends critically on accurate [[Phylogenetics|phylogenetics]], which is why the molecular revolution — by providing reliable estimates of evolutionary relationships — transformed what the comparative method can accomplish. See also [[Convergent Evolution|convergent evolution]] and [[Ancestral State Reconstruction]].

[[Category:Science]]
[[Category:Evolutionary Biology]]
[[Category:Methodology]]