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This chapter explores variational structuralism, whose core idea is that organisms and their parts play causal roles in shaping the patterns of phenotypic evolution. Drawing on the work of pioneers such as Ron Amundson, it discusses the conceptual incompatibilities between two styles of thinking in evolutionary biology: functionalism and structuralism. It proceeds by explaining the meaning of developmental types and structuralist concepts arising from macromolecular studies. It also examines facts and ideas about bodies, Rupert Riedl's theory of the “immitatory epigenotype,” and Neil Shubin and Pere Alberch's developmental interpretation of tetrapod limbs. Finally, it looks at the emergence of molecular structuralism and the enigma of developmental variation. The chapter argues that typology naturally emerged from the facts of evolutionary developmental biology and that it would be seriously problematic to try to avoid it.

The hierarchy theory at its onset was primarily committed to vindicate the distinctness of macro-evolutionary phenomena from micro-evolutionary processes, minimizing the explanatory relevance of levels and entities below the organism and above the gene. The current focus on phenotypic evolution, however, suggests a refinement and revision of the role of the so-called “somatic” or “phenotypic hierarchy”, and the evolutionary bearing of its structured variability at different levels. The paper reviews some theoretical reasons and implications of such reassessment.

Bilaterian animal body plan origins are generally thought about in terms of adult forms. However, most animals have larvae with body plans, ontogenies, and ecologies distinct from their adults. The first of two primary hypotheses for larval origins suggests the earliest animals were small pelagic forms similar to modern larvae, with adult bilaterian body plans evolved subsequently. The second suggests that adult bilaterian body plans evolved first and that larval body plans arose by interpolations of features into direct-developing ontogenies. The two hypotheses have different consequences for understanding parsimony in evolution of larvae and of developmental genetic mechanisms. If primitive metazoans were like modern larvae and distinct adult forms evolved independently, there should be little commonality of patterning genes among adult body plans. However, sharing of patterning genes in adults is observed. If larvae arose by co-option of adult bilaterian-expressed genes into independently evolved larval forms, larvae may show morphological convergence, but with distinct patterning genes, as is observed. Thus, comparative studies of gene expression support independent origins of larval features. Precambrian and Cambrian embryonic fossils are also consistent with direct development of the adult as primitive, with planktonic larval forms arising during the Cambrian. Larvae have continued to co-opt genes and evolve new features, allowing study of developmental evolution.

This chapter explores the questions of how the mind’s diverse mechanisms evolve as a whole and how they are organized. It describes a hierarchical view of brain architecture in which modules evolve via descent with modification from ancestral structures, leading to a mosaic of shared and divergent features. The shaping of epigenetic processes of brain development is described.

This chapter lays out a framework for understanding the evolution of developmental systems. It presents the biological concept of a reaction norm, a mapping between developmental circumstances and phenotypic outcomes, and suggests that this concept, suitably broadened, can capture the development of all mental phenotypes, bridging the nature/nurture divide.

This Festschrift for Chris Humphries provides an opportunity to reflect on how much has changed in systematic biology since the 1970s. Humphries, together with his longtime collaborator, Kåre Bremer, pioneered the application of cladistic methods of phylogeny reconstruction in the Compositae and soon influenced the systematics of other groups of living and fossil plants. Today, the classification of the Compositae has been turned literally upside-down thanks to the availability of DNA sequence characters and the almost universally adopted procedures of phylogenetic systematics. There can be little doubt that Humphries's pivotal role in the promotion of cladistics was greatly enhanced by his appointment to the Department of Botany at the (then) British Museum (Natural History). This chapter focuses on Humphries's contribution to the field of evolution and development. It considers how the field of ontogeny and systematics has developed through to the present day, with particular emphasis on pollen ontogeny. It concluded that Humphries played an influential role in the emergence of the discipline now recognized as “evo-devo”: evolutionary developmental biology.

Evolutionary developmental biology, or Evo Devo, examines how developmental mechanisms affect evolutionary change. Heterochrony refers to genetic-based differences in developmental timing. One important type of heterochrony for humans is neoteny, which refers to the retention of juvenile traits into later development. Humans are a neotenous species, as seen in infants’ features of “babyness,” which promote attention and caring from adults, extending the primate prenatal brain growth rate well past birth, and a reduction of reactive aggression relative to great apes, which facilitated increased cooperation among group members. Homo sapiens extended the time it takes to reach adulthood by inventing new two life stages—childhood and adolescence. The social and cognitive abilities of Homo sapiens’ youth may be well suited to the childhood and adolescent stages and to the attainment of skills necessary for developing into functional adults.

This chapter presents four lines of argumentation for the claim that the emergence of language can and should be explained as a culturally driven process that eventually entangled individual mind/brains in a process of evolution for language: (1) capacities and their genetic accommodation emerge from exploration and innovation, not the other way around; (2) the emergence of language as a communication technology must have required collaborative exploration and innovation; (3) language requires some relatively specific capacities, which can only be explained through a process of accommodation for the specificities of language as a technology; (4) apes can learn a protolangauge, but cannot invent it by themselves.