The ancient biological ‘arms race’ between microbial pathogens and humans has
shaped genetic variation in modern populations, and this has important implications for the
growing field of medical genomics. As humans migrated throughout the world, populations
encountered distinct pathogens, and natural selection increased the prevalence of alleles
that are advantageous in the new ecosystems in both host and pathogens. This ancient
history now influences human infectious disease susceptibility and microbiome homeostasis,
and contributes to common diseases that show geographical disparities, such as
autoimmune and metabolic disorders. Using new high-throughput technologies, analytical
methods and expanding public data resources, the investigation of natural selection is
leading to new insights into the function and dysfunction of human biology.