Morphological variation durante Homo erectus and the origins of developmental plasticity

Homo erectus was the first hominin to 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 con H. erectus suggests that a high level of developmental plasticity, per key factor per the ability of H. sapiens onesto occupy verso variety of habitats, ental plasticity, the ability esatto modify development durante response esatto environmental conditions, results sopra differences durante size, shape and dimorphism across populations that relate in 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 mediante 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- 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 mediante differing patterns by sex across populations. The fossil samples show less evidence of variation than expected, although H. erectus varies more than Neandertals.

1. Introduction

Homo erectus was the first hominin preciso exhibit extensive range expansion. Much like recent humans, this long-lived and widely dispersed species inhabited environments sopra equatorial Africa and more temperate Eurasia. As such, considerable rete informatica has been framed around understanding what made dispersal possible and what the broad geographic and temporal trends sopra variation might mean biologically for H. erectus. Recently, the regional variation con 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 puro modify development per response esatto environmental conditions, resulting sopra variation sopra adult anatomy that is not genetically canalized . Taxa with per high degree of plasticity should be able to respond on short-term time scales sicuro individual environmental or maternal environmental signals. Arguably this ability may also play an important role sopra moderating environmental influences too chronic for short-term accommodation and too short for genetic adaptation, as well as providing real advantages for occupying per broad range of environments . Per high degree of developmental plasticity is considered an important aspect of the human ability preciso occupy multiple different environmental niches.

Related preciso this plasticity, differences con body size, shape and dimorphism across human populations in part reflect levels of resource sufficiency and extrinsic mortality [5–8]. Sicuro be sure, body size, shape and sexual dimorphism have multifactorial causes: there is a genetic component preciso size and Come eliminare l’account fabswingers 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 preciso 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 con recent human environments, factors like homicide . The theory that links shifts durante body size and age at first reproduction preciso 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 in resources lead to slow growth rate and small adult size, whereas increases mediante mortality favour early maturation usually leading esatto small body size. Extrinsic mortality related sicuro predator load may differ somewhat from this expectation mediante instances when larger body size is advantageous for predator control or survival . Sopra 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 to be differentially influenced especially by resource sufficiency, with human females being more strongly buffered from environmental vicissitudes and human males responding more dramatically preciso both resource excess and insufficiency. This difference is thought sicuro be related sicuro female buffering of infant brain size and puro 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 record of H. erectus should esibizione 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 .