Figure 1. The two genes INS and IGF2 were derived from a duplication event in an ancestral species. Speciation then split species into human and chicken. The INS genes in human and chicken are orthologous, and so are the IGF2 genes, but the INS genes are paralogous to the IGF2 genes.

Figure 2. The relative-rate test used to compare the rates of chromosome change in the human (x) and mouse (y) lineages. The diagram shows the rooted tree for human, mouse and chicken, using chicken as the known outgroup. O, denotes the common ancestor of human and mouse.

Figure 3. Number of chromosome rearrangements between nodes of the phylogenetic tree of birds and mammals. On the left is a scale in millions of years ago (Mya). The circles represent the estimated times of divergence of common ancestors for birds/mammals (300 Mya), rodents and other mammals (100 Mya), and nonrodent mammals (65 Mya). The horizontal broken line represents the Cretaceous–Tertiary (K–T) boundary. The approximate number of chromosome rearrangements is shown along each lineage and in brackets are the rates of chromosomal rearrangement per My. These estimates are based on genetic linkage (including possible ranges) and Zoo-FISH data. Adapted from Burt et al., (1999).