7 - The role of diet and epigenetics in migration: molecular mechanisms underlying the consequences of change

Summary

Introduction

Genotypes establish the developmental parameters and constraints on human traits, but environmental factors interacting with genes ultimately shape many phenotypes. These resulting phenotypes must prove beneficial for both survival and reproduction to continue any species. During their evolutionary history, human beings have demonstrated great capacity for survival and reproductive success while adapting to a wide range of environments. By interacting with increasingly complex cultural strategies to manage environmental advantages, genetic variation found in the human genome supported the human ancestral migrations out of Africa and around the globe. However, the manner by which genes and environment communicate to affect phenotypes remains unclear. The plasticity seen in fetal development and neonatal growth patterns appears to reflect the presence of early physiological acclimatization to environmental signals (Cutfield et al., 2007). Such signals leave lasting directives for gene expression, metabolic pathways and future adaptation capabilities without DNA mutation (Waterland and Garza, 1999). Additionally, these signals provide potentially reversible regulations of gene expression that more rapidly respond to environmental fluctuation than responses originating through changes in the DNA sequencing (Burdge et al., 2007). These “epigenetic” regulatory signals are transgenerational (Haig, 2004), yet the patterns are less robust across generations given their responsiveness to the environment. The reversible nature of these signal mechanisms leaves many unanswered questions regarding the mode of environmental influence on phenotypic development during human evolution. Today’s migrating populations experiencing rapid and dramatic changes in climate, food chain, social, and economic factors provide a unique model for testing the epigenetic hypotheses in humans.