Morphological variation sopra Homo erectus and the origins of developmental plasticity
Homo erectus was the first hominin sicuro exhibit extensive range expansion. This extraordinary departure from Africa, especially into more temperate climates of Eurasia, has been variously related to technological, energetic and foraging shifts. The temporal and regional anatomical variation sopra H. erectus suggests that verso high level of developmental plasticity, per key factor per the ability of H. sapiens puro occupy verso variety of habitats, ental plasticity, the ability to modify development mediante response puro environmental conditions, results mediante differences in size, shape and dimorphism across populations that relate durante part sicuro 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 con instances of resource scarcity and high predator load. We consider the metric variation in 35 human and non-human arcivescovo ‘populations’ from known environmental contexts and 14 time- 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 spettacolo less evidence of variation than expected, although H. erectus varies more than Neandertals.
1. Introduction
Homo erectus was the first hominin sicuro exhibit extensive range expansion. Much like recent humans, this long-lived and widely dispersed species inhabited environments con equatorial Africa and more temperate Eurasia. As such, considerable sistema has been framed around understanding what made dispersal possible and what the broad geographic and temporal trends mediante variation might mean biologically for H. erectus. Recently, the regional variation per 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 onesto modify development con response onesto environmental conditions, resulting in variation durante adult anatomy that is not genetically canalized . Taxa with a high degree of plasticity should be able esatto respond on short-term time scales puro individual environmental or maternal environmental signals. Arguably this ability may also play an important role con moderating environmental influences too chronic for short-term accommodation and too short for genetic adaptation, as well as providing real advantages for occupying verso broad range of environments . A high degree of developmental plasticity is considered an important aspect of the human ability onesto occupy multiple different environmental niches.
Related onesto this plasticity, differences per body size, shape and dimorphism across human populations per part reflect levels of resource sufficiency and extrinsic mortality [5–8]. Onesto be sure, body size, shape and sexual dimorphism have multifactorial causes: there is per genetic component puro 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 onesto body size outcomes. Resource sufficiency includes any variable that influences the nutritional segno, 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 durante recent human environments, factors like homicide . The theory that links shifts sopra body size and age at first reproduction onesto 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 to slow growth rate and small adult size, whereas increases sopra mortality favour early maturation usually leading puro small body size. Extrinsic mortality related sicuro predator load may differ somewhat from this expectation in instances when larger body size is advantageous for predator control or survival . Con these instances, early maturation but faster growth may favour the retention of large size, particularly per males. Mediante humans, males and females are often argued puro be differentially influenced especially by resource sufficiency, with human females being more strongly buffered from environmental vicissitudes and human males responding more dramatically puro both resource excess and insufficiency. This difference is thought puro be related onesto female buffering of infant brain size and onesto 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 primato prezzi grindr of H. erectus should spettacolo not only regional variations, but also overall smaller adult body sizes and lower levels of dimorphism per populations experiencing resource scarcity and high extrinsic mortality if the species shows human-like levels of plasticity .
