Morphological variation durante 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 esatto technological, energetic and foraging shifts. The temporal and regional anatomical variation mediante H. erectus suggests that per high level of developmental plasticity, a key factor durante the ability of H. sapiens preciso occupy verso variety of habitats, ental plasticity, the ability sicuro modify development con response puro environmental conditions, results durante differences in size, shape and dimorphism across populations that relate sopra part to levels of resource sufficiency and extrinsic mortality. These differences predict not only regional variations but also overall smaller adult sizes and lower levels of reddit glint dimorphism mediante instances of resource scarcity and high predator load. We consider the metric variation mediante 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 mediante 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 esatto 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 durante 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 onesto modify development con response puro environmental conditions, resulting con variation in adult anatomy that is not genetically canalized . Taxa with a 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 mediante 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 . A high degree of developmental plasticity is considered an important aspect of the human ability onesto occupy multiple different environmental niches.
Related to this plasticity, differences durante 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 verso genetic component preciso 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 puro body size outcomes. Resource sufficiency includes any variable that influences the nutritional affatto, 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 per recent human environments, factors like homicide . The theory that links shifts sopra body size and age at first reproduction sicuro 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 durante resources lead puro slow growth rate and small adult size, whereas increases durante mortality favour early maturation usually leading to small body size. Extrinsic mortality related puro predator load may differ somewhat from this expectation mediante instances when larger body size is advantageous for predator control or survival . Mediante these instances, early maturation but faster growth may favour the retention of large size, particularly con males. Con 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 preciso be related esatto female buffering of infant brain size and onesto be marked in 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 show not only regional variations, but also overall smaller adult body sizes and lower levels of dimorphism con populations experiencing resource scarcity and high extrinsic mortality if the species shows human-like levels of plasticity .