Fig. 2
From: Sociobiology and the Comparative Approach: One Way to Study Ourselves
Identifying convergent evolution on a phylogenetic tree. The hypothesis that the character “homeothermy (warm-bloodedness)” is “the same” (=homologous) in mammals and birds is refuted when we place homeothermy on a phylogenetic tree constructed from hundreds of other characters. The phylogenetic patterns indicate that poikilothermy (cold-bloodedness) is the ancestral state for this large group and that homeothermy has originated twice from that state. Homeothermy is thus a convergent trait. Asterisks = homeothermy