Parsimony

mammary glands

Figure 3.10. Two possible arrangements for the relationships of birds, bats, and humans. (a) The left-hand cladogram requires wings to have evolved two times; (b) the right-hand cladogram requires birds to have lost fur and mammary glands. These as well as many other characters suggest that (a) is the more parsimonious of the two cladograms.

mammary glands

Figure 3.10. Two possible arrangements for the relationships of birds, bats, and humans. (a) The left-hand cladogram requires wings to have evolved two times; (b) the right-hand cladogram requires birds to have lost fur and mammary glands. These as well as many other characters suggest that (a) is the more parsimonious of the two cladograms.

Indeed, as a hypothesis about the evolution of these vertebrates, it is much more likely that bats and humans share a more recent common ancestor than that either does with a bird (which, obviously, is why bats and humans are classified together here as mammals). In this case, the use of shared, derived characters has led us to the most parsimonious conclusion with regard to the evolution of these three creatures.

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