Morphological variation in Homo erectus and the origins of developmental plasticity
Homo erectus was the first hominin preciso exhibit extensive range expansion. This extraordinary departure from Africa, especially into more temperate climates of Eurasia, has been variously related onesto technological, energetic and foraging shifts. The temporal and regional anatomical variation mediante H. erectus suggests that per high level of developmental plasticity, verso key factor in the ability of H. sapiens esatto occupy a variety of habitats, ental plasticity, the ability preciso modify development per response esatto environmental conditions, results in differences durante size, shape and dimorphism across populations that relate per part preciso levels of resource sufficiency and extrinsic mortality. These differences predict not only regional variations but also overall smaller adult sizes and lower levels of dimorphism in instances of resource scarcity and high predator load. We consider the metric variation per 35 human and non-human alto prelato ‘populations’ from known environmental contexts and 14 time- datemyage sito mobile and space-restricted paleodemes of H. erectus and other fossil Homo. Human and non-human primates exhibit more similar patterns of variation than expected, with plasticity evident, but durante differing patterns by sex across populations. The fossil samples esibizione less evidence of variation than expected, although H. erectus varies more than Neandertals.
1. Introduction
Homo erectus was the first hominin onesto exhibit extensive range expansion. Much like recent humans, this long-lived and widely dispersed species inhabited environments durante equatorial Africa and more temperate Eurasia. As such, considerable rete di emittenti has been framed around understanding what made dispersal possible and what the broad geographic and temporal trends in variation might mean biologically for H. erectus. Recently, the regional variation sopra H. erectus has been described as ‘human-like’ , and by extension we have suggested that the dispersal and evolutionary longevity of the species ental (phenotypic) plasticity [2,3].
Developmental (phenotypic) plasticity is the ability sicuro modify development sopra response sicuro environmental conditions, resulting sopra variation durante adult anatomy that is not genetically canalized . Taxa with a high degree of plasticity should be able preciso respond on short-term time scales sicuro individual environmental or maternal environmental signals. Arguably this ability may also play an important role per moderating environmental influences too chronic for short-term accommodation and too short for genetic adaptation, as well as providing real advantages for occupying a broad range of environments . Verso high degree of developmental plasticity is considered an important aspect of the human ability esatto occupy multiple different environmental niches.
Related preciso this plasticity, differences in body size, shape and dimorphism across human populations in part reflect levels of resource sufficiency and extrinsic mortality [5–8]. Preciso be sure, body size, shape and sexual dimorphism have multifactorial causes: there is per genetic component sicuro size and variation, and other environmental conditions such as temperature also influence the attainment of adult size. The latter is reasonably well understood, allowing consideration of other contributions sicuro body size outcomes. Resource sufficiency includes any variable that influences the nutritional questione, some of which are co-correlated with aspects of climate such as rainfall and seasonality. Extrinsic mortality can be defined generally as the external risks of mortality such as predator and parasite load, or in recent human environments, factors like homicide . The theory that links shifts in body size and age at first reproduction esatto resource sufficiency and extrinsic mortality is relatively clear . Resource sufficiency is positively correlated with extrinsic mortality and negatively correlated with adult body size; that is, decreases sopra resources lead esatto slow growth rate and small adult size, whereas increases sopra mortality favour early maturation usually leading puro small body size. Extrinsic mortality related esatto predator load may differ somewhat from this expectation con instances when larger body size is advantageous for predator control or survival . Per these instances, early maturation but faster growth may favour the retention of large size, particularly con males. In humans, males and females are often argued onesto be differentially influenced especially by resource sufficiency, with human females being more strongly buffered from environmental vicissitudes and human males responding more dramatically sicuro both resource excess and insufficiency. This difference is thought sicuro be related puro female buffering of infant brain size and esatto be marked con humans for this reason . Such differential influence can alter dimorphism values if the female size change differs from that of males . Extrapolating from living humans, this logic predicts that the skeletal supremazia of H. erectus should show not only regional variations, but also overall smaller adult body sizes and lower levels of dimorphism mediante populations experiencing resource scarcity and high extrinsic mortality if the species shows human-like levels of plasticity .