2/28/2024 0 Comments Pygmy falcon size![]() 22, studying anthropometric measurements and life history variables in populations with a short stature from the Philippines (Aeta), have suggested that their life history variables develop at an early stage in life and that the short stature of these groups is due to relatively earlier cessation of growth. Since the average rate of height gain during this spurt is around 9 cm year in boys (total spurt around 25 cm) and 7 cm per year in girls (total spurt around 20 cm) in most human populations 21, the absence of this spurt could easily explain the short stature of pygmies. Merimee 20, based on blood analyses of Aka pygmies from the Central African Republic, has suggested that the short stature of pygmies could be accounted for by the absence of an adolescent growth spurt because, during this period of growth, pygmies have a low content of IGF1 (pituitary GH effector and hormonal stimulator of cell growth, proliferation and differentiation, particularly in the growth plate). Although some particular SNPs in genes associated with stature have been identified in pygmies 17, 18, the exact genetic foundation remains elusive 19.įew studies have suggested any explanation to account for when and how the pygmy phenotype is achieved during individual growth. ![]() Studies of genetic introgression have shown that the pygmy phenotype stems from genetic foundations 15, perhaps involving a deficiency in the GH–IGF axis 16. The pygmy phenotype itself is usually interpreted as an adaptation to life in equatorial rain forests 5. Even today, the main barriers to admixture are the cultural and behavioural differences between these two groups 7. Substantial admixtures between pygmies and non-pygmies have occurred in the last ∼1,000 years 14. Pygmies share a common ancestor and splitted from Bantu-speaking populations at around 60,000 years BP 13 the split into an eastern and a western cluster would have taken place later than 20,000 years BP 13. The other cluster, in West Africa (Cameroon, Central Africa Republic, Congo, Gabon and Western DRC), includes the Kola, Bongo, Koya, Aka, Baka and Twa. One is in East Africa (Ruanda, Uganda and Eastern DRC) and comprises (following Schebesta 9, Gusinde 10 and many others 11, 12 nomenclature) the Aka, Sua, Efe groups (also frequently called ‘Mbuti’) and the Batwa. Pygmy populations are distributed across equatorial Africa in two main clusters. Moreover, in each case pygmy peoples are identified by their culture and behaviour as pygmies by farming neighbours, who in turn identify themselves as non-pygmies and are recognized as non-pygmies by pygmies, as well as by other non-pygmies 7, 8. They share an economy based on hunting and gathering and a complex socioeconomic relationship with their farming neighbours. ![]() ![]() Furthermore, although other groups of short average stature live in different environments 4, 5, restricting the use of ‘Pygmies’ to groups who share particular socioeconomic and cultural behaviour patterns and inhabit a similar environment provides a basis for investigations into their anatomical adaptation.Īfrican pygmies live in equatorial rain forests and grow to an average adult stature of <155 cm 6. Since genetic studies have suggested that African pygmies share a common ancestor, restricting the word ‘pygmies’ to African populations provides a biological foundation for the term. The term ‘pygmies’ has been widely used for all of them but with no biological foundation. Human populations with short stature exist on all continents. Populations of short average stature, such as African pygmies, show that growth patterns vary among modern humans, although the mechanisms responsible and their impact on the evolution of modern humans are not well understood. Dwarf populations are considered to be the descendants of groups inhabiting the mainland and are regarded as particular sub-species or distinct species. The ‘island rule’ does not only account for these phenomena in geographic islands as it is also observed in ‘environmental islands’, where patches of a particular environment are located within and surrounded by other very different environments 3. Dwarfism is in fact an endemic phenomenon observed in several orders of mammals inhabiting islands, which is probably due to the lack of predation pressure and exposure to limited resources 2. Dwarfism is not restricted to humans: it is part of the so-called ‘island rule’, a tendency in vertebrates towards gigantism in small species and dwarfism in large species 1. Short stature in human populations is of particular interest to geneticists and evolutionary and cultural anthropologists, as well as to physicians and sociologists.
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