Genetic differentiation in East African ethnicities and its relationship with endurance running success

Abstract

Since the 1960s, East African athletes, mainly from Kenya and Ethiopia, have dominated long-distance running events in both the male and female categories. Further demographic studies have shown that two ethnic groups are overrepresented among elite endurance runners in each of these countries: the Kalenjin, from Kenya, and the Oromo, from Ethiopia, raising the possibility that this dominance results from genetic or/and cultural factors. However, looking at the life history of these athletes or at loci previously associated with endurance athletic performance, no compelling explanation has emerged. Here, we used a population approach to identify peaks of genetic differentiation for these two ethnicities and compared the list of genes close to these regions with a list, manually curated by us, of genes that have been associated with traits possibly relevant to endurance running in GWAS studies, and found a significant enrichment in both populations (Kalenjin, P = 0.048, and Oromo, P = 1.6x10-5). Those traits are mainly related to anthropometry, circulatory and respiratory systems, energy metabolism, and calcium homeostasis. Our results reinforce the notion that endurance running is a systemic activity with a complex genetic architecture, and indicate new candidate genes for future studies. Finally, we argue that a deterministic relationship between genetics and sports must be avoided, as it is both scientifically incorrect and prone to reinforcing population (racial) stereotyping.

Fig 1

A) Place of birth of the 100 best marathon runners of all time, men and women, as listed by the International Association of Athletics Federations on June 29, 2019. Note the large fraction corresponding to Kenya and Ethiopia, in both sexes. B) Approximate locations for the African ethnolinguistic groups (populations) used in this study.

Fig 2. Overview of the study design.

For each country, Ethiopian and Kenya, ethnicities overrepresented among endurance running athletes, Oromo and Kalenjin, respectively, were compared to populations that are underrepresented among athletes, Amhara and Luhya, respectively. Note that all populations may contain individuals that are genetically predisposed to endurance running or not, though in different proportions. Population comparisons allowed the identification of genome regions highly differentiated in Oromo and Kalenjin and the genes in their vicinity. The list of genes was then interrogated for enrichment for phenotypic traits that may be relevant for endurance running, such as heart function, energy metabolism, anthropometric traits, calcium homeostasis, and lung function, among others. Please see the Methods for a detailed description of all steps performed during the study.

Fig 3. Manhattan plots of PBSn1 values for Kalenjin and Oromo considering all comparisons (see Material and Methods for details).

Each dot represents a window of 20 SNPs. The blue line indicates the 0.1% highest values. Note the different scale among comparisons. Genes associated with the five non-intergenic windows with the highest PBSn1 are shown. For the complete list of genes, see S1 Dataset.