| Citation | Peter Holland is distinguished for conceptually and empirically unifying two research fields ? the genetic control of development and the molecular evolution of genes. He initiated a systematic examination of how homeobox and other genes evolved during animal radiation. He characterised the structure of homeobox genes of amphioxus, a species chosen for its evolutionary significance; unlike vertebrates it has a single set of Hox genes. He demonstrated the increase in Hox gene cluster complexity accompanying the emergence of the vertebrates, how those genes acquired new roles after duplication, and disproved the notion that cephalochordates are degenerate vertebrates. Holland pioneered investigations to place Hox genes in the context of the whole genome, revealing that chordates underwent a burst of extensive gene duplication near the time of vertebrate origins. He proposed the concept of `molecular landmarks' which solves the longstanding `head problem': the vertebrate head is not a neomorph but evolved from a latent precursor region. Holland has also demonstrated that the Hox cluster is not universal in Metazoa but arose in triploblast evolution as a product of an older set of genes which acquired roles in patterning endoderm. |