The article by Dehal and Boore (2005) investigates the hypothesis that the complex vertebrate genome resulted from two ancient whole genome duplications (WGD). They analyzed gene families from the complete gene sets of a tunicate, fish, mouse, and human to determine the timing and extent of gene duplications. Despite previous studies suggesting a strong signal of these events, Dehal and Boore found little evidence of WGD in gene family numbers, tree topology, or gene per family sizes. However, when they examined the genomic positions of paralogous genes that duplicated before the fish-tetrapod split, they identified clear patterns of four-way paralogous regions, indicating two distinct genome duplication events early in vertebrate evolution. These findings highlight the potential role of these large-scale genomic events in driving the evolutionary success of vertebrates. The authors conclude that the 2R hypothesis is supported by the global physical organization of paralogous genes, which remains robust despite extensive genome rearrangements and gene losses over 450 million years of evolution.The article by Dehal and Boore (2005) investigates the hypothesis that the complex vertebrate genome resulted from two ancient whole genome duplications (WGD). They analyzed gene families from the complete gene sets of a tunicate, fish, mouse, and human to determine the timing and extent of gene duplications. Despite previous studies suggesting a strong signal of these events, Dehal and Boore found little evidence of WGD in gene family numbers, tree topology, or gene per family sizes. However, when they examined the genomic positions of paralogous genes that duplicated before the fish-tetrapod split, they identified clear patterns of four-way paralogous regions, indicating two distinct genome duplication events early in vertebrate evolution. These findings highlight the potential role of these large-scale genomic events in driving the evolutionary success of vertebrates. The authors conclude that the 2R hypothesis is supported by the global physical organization of paralogous genes, which remains robust despite extensive genome rearrangements and gene losses over 450 million years of evolution.