| Project 1: | Adaptive Evolutionary Heritage - Heterochony and allometry in the evolution of human ontogeny |
| Principal Investigators: | Dr. Marta Mirazón Lahr & Dr. Robert A. Foley |
| Co-Investigator: | Dr. Lucio Vinicius Castilho |
| Collaborators: | Dr. Jay Stock, Prof. Barry Keverne, Prof. Pat Bateson, Dr. Nick Mundy |
| Funding: | The Leverhulme Trust |
Much has been learnt about the genetics of human growth. Phenotypic studies are an essential complement to genetics if an integrated view of humans at the individual and species level is envisaged. This theme will investigate the selective and morphological mechanisms that underlie the changes leading to the human growth pattern, thus work towards a theory of human growth and development.
At the level of organisms, phenotypes are the outcome of the interaction between genetics and environment, defining the phenomenon of plasticity. On both theoretical and experimental grounds human plasticity is expected to be adaptive, but it is rarely seen from this perspective. This can be approached by focusing on the analysis of variation in growth trajectories (allometry) and timing of development (heterochrony) at the populational level, as a preamble to understanding how growth responds to selective pressures. A second level of integration places growth as a dimension of life history, and as such, as a complex target for selection, giving its correlation (trade-offs) with reproduction, longevity, and sociality for example. Differences in size and shape of an organism, and indeed of its behaviour, arise from differences in developmental programme. This has sometimes been characterised in human evolution in terms of neoteny - making adults more child-like, although this is an oversimplification of a more complex process. Studies of growth in the context of life history variables are thus fundamental for a more complete evolutionary appraisal of human growth and development, and vice versa. Theoretical frameworks for this are available, but need to be more thoroughly applied and developed in the human context. Hominin evolution can be used to investigate the nature of inter-specific changes in growth trajectories and timing in terms of their ecological, behavioural and morphological contexts. The variability in growth patterns among recent and current populations can be explored analytically to disclose the intra-specific processes promoting and constraining development. Additionally, a huge descriptive database for human populations and their life history parameters is being used to test these evolutionary models. This theme will integrate the fields of human growth and evolution on the one hand, and life history theory and human variability on the other by focusing on variation in hominid and human size and shape (anthropometry and biometry at various levels) in the context of growth patterns.
The phenotypic patterns of growth upon which allometric and heterochronic mechanisms operate are genetically determined, and characterised a species' overall life-history and developmental trajectory. Nevertheless, the integrated nature of multivariate growth means that alterations on single parameters will have domino-like effects on other aspects of size, shape and life-history. Thus, relatively simple and singular genetic changes can result in novel morphologies and life-history scheduling. Only through the identification of the systems upon which selection has acted, and their effects on the growth and biology of the entire organism, can the genetic traits that differentiate humans be identified.
In sum, the main aim of this post-genomics initiative is to develop a more theoretical approach to human growth using insights drawn from evolution (comparative heterochrony, growth fields and allometry), genetics and ecology, and testing these in anthropological contexts.