Global spatial patterns of infectious diseases and human evolution

Abstract

Geographical aspects of human diseases Latitude affects the diversity and distribution of many free-living organisms, but little is known about large-scale patterns of the distribution of human or animal pathogens (Finlay 2002). One

Evolution of pathogens in a man‐made world

“…Then, during the course of human evolution, the habitat expanded gradually into the more temperate zones. Hominids thus transported some other diseases en route with the human expansion, and acquired new pathogen agents living in the newly colonized territories (Guégan et al . 2007).…”

“…Within the last 300 years, transportation has played a major role in shaping disease patterns by bringing larger segments of human populations into close contact with pathogens at an accelerated rate (Renaud et al . 2005; Guégan et al . 2007).…”

“…2003). The past decade has even seen the emergence and resurgence of many infectious diseases around the world with the majority of them being zoonoses (Guégan et al . 2007).…”

Genes: Interactions with Language on Three Levels—Inter-Individual Variation, Historical Correlations and Genetic Biasing

“…In some people, a point mutation in the HBB gene on chromosome 11 (this mutation is known as HbS), results in the substitution of one amino acid for another and the production of a malfunctioning haemoglobin molecule. When an individual is homozygous for this mutation, it will produce only malfunctioning haemoglobin, manifested as sickle cell anemia, a complex disease which usually kills before puberty (Guégan et al 2007, see OMIM 603903 for details). However, a heterozygous carrier will have a more or less normal phenotype, as the normal (wild-type, denoted HbA) copy of the gene will produce enough functioning red blood cells to compensate for the mutated ones.…”

“…Interestingly, these heterozygous individuals actually suffer less from malaria, a deadly infectious disease caused by a parasite of the red blood cells (genus Plasmodium, the most dangerous being the falciparum species), transmitted through mosquito (genus Anopheles) bites. Thus, the HbS mutation, on one hand, is very deleterious in homozygous form (HbS-HbS) by causing sickle cell anemia, but is better than the normal homozygous (HbA-HbA) when in heterozygous form (HbS-HbA) in environments where malaria is endemic (Guégan et al 2007;Cavalli-Sforza et al 1994). This phenomenon is called heterozygote advantage and explains why some alleles deleterious in homozygous form are, nevertheless, maintained at relatively high frequencies, in the population (Cavalli-Sforza et al 1994;Skelton 1993): in a sense, this is a cost some have to pay for the benefit of many.…”