A neonatal perspective on Homo erectus brain growth

Cofran, Zachary; DeSilva, Jeremy M.

doi:10.1016/j.jhevol.2015.02.011

Cited by 31 publications

(21 citation statements)

References 49 publications

(73 reference statements)

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“…This practice has a proven impact on several other factors distinguishing human evolution and psychology, such as intersubjective abilities, proactive pro-sociality, brain size and altriciality (Hrdy, 2009(Hrdy, , 2016Isler and van Schaik, 2012;Burkart et al, 2014). Alloparenting may have emerged quite early in the hominin line because (i) cooperative breeding is especially likely to evolve in ecologically unstable environments (Hrdy, 2016); (ii) Australopithecus females were estimated to have given birth to babies who were more than 5% of their adult body mass compared to 3% in chimpanzees and 6% in modern humans (DeSilva, 2011); and (iii) there is evidence for extended altriciality in Homo erectus (Cofran and DeSilva, 2015). Strong trust relationships have to be formed in order for mothers to allow others access to their young: chimpanzee mothers, for example, are highly protective.…”

Section: Human Social Evolution Social Emotions and Emotional Plasticmentioning

confidence: 99%

Human Social Evolution: Self-Domestication or Self-Control?

et al. 2020

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The self-domestication hypothesis suggests that, like mammalian domesticates, humans have gone through a process of selection against aggression-a process that in the case of humans was self-induced. Here, we extend previous proposals and suggest that what underlies human social evolution is selection for socially mediated emotional control and plasticity. In the first part of the paper we highlight general features of human social evolution, which, we argue, is more similar to that of other social mammals than to that of mammalian domesticates and is therefore incompatible with the notion of human self-domestication. In the second part, we discuss the unique aspects of human evolution and propose that emotional control and social motivation in humans evolved during two major, partially overlapping stages. The first stage, which followed the emergence of mimetic communication, the beginnings of musical engagement, and mimesis-related cognition, required socially mediated emotional plasticity and was accompanied by new social emotions. The second stage followed the emergence of language, when individuals began to instruct the imagination of their interlocutors, and to rely even more extensively on emotional plasticity and culturally learned emotional control. This account further illustrates the significant differences between humans and domesticates, thus challenging the notion of human self-domestication.

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Section: Human Social Evolution Social Emotions and Emotional Plasticmentioning

confidence: 99%

Human Social Evolution: Self-Domestication or Self-Control?

et al. 2020

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“…). Homo erectus is hypothesized to have followed a brain growth trajectory that combined human‐like and great ape‐like features (O'Connell & DeSilva, ; Cofran & DeSilva, ). Neanderthals likely exhibited even higher early postnatal brain growth rates than modern humans (Ponce de León et al.…”

Section: Introductionmentioning

confidence: 99%

“…Australopithecus africanus is thought to have exhibited a great ape-like brain growth trajectory (Zollikofer & Ponce de Le on, 2013), while there is evidence that A. afarensis had a more human-like trajectory (Alemseged et al 2006). Homo erectus is hypothesized to have followed a brain growth trajectory that combined human-like and great ape-like features (O'Connell & DeSilva, 2013;Cofran & DeSilva, 2015). Neanderthals likely exhibited even higher early postnatal brain growth rates than modern humans (Ponce de Le on et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Effects of cranial integration on hominid endocranial shape

2016

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Because brains do not fossilize, the internal surface of the braincase (endocast) serves as an important source of information about brain growth, development, and evolution. Recent studies of endocranial morphology and development in great apes, fossil hominins, and modern humans have revealed taxon-specific differences. However, it remains to be investigated to which extent differences in endocranial morphology reflect differences in actual brain morphology and development, and to which extent they reflect different interactions of the brain and its case with the cranial base and face. Here we address this question by analyzing the effects of cranial integration on endocranial morphology. We test the 'spatial packing' and 'facial orientation' hypotheses, which propose that size and orientation of the neurocranium relative to the viscerocranium influence endocranial shape. Results show that a substantial proportion of endocranial shape variation along and across ontogenetic trajectories is due to cranial integration. Specifically, the uniquely globular shape of the human endocast mainly results from the combination of an exceptionally large brain with a comparatively small face. Overall, thus, cranial integration has pervasive effects on endocranial morphology, and only a comparatively small proportion of inter- and intra-taxon variation can directly be associated with variation in brain morphology.

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“…These approaches could be used in other comparative studies in evolutionary anthropology and human evolution. For example, these analyses could be added to the repertoire of paleoanthropologists, who already use randomization and resampling procedures to make conclusions utilizing small samples or single specimens (e.g., Lockwood, 1999; Cardini and Elton, 2007; Cofran and DeSilva, 2015) and are increasingly incorporating phylogenetic comparative methods in their research (e.g., Pontzer et al, 2014; Gonzales et al, 2015; Pampush, 2015; Russo, 2016). …”

Section: Discussionmentioning

confidence: 99%

Assessing sources of error in comparative analyses of primate behavior: Intraspecific variation in group size and the social brain hypothesis

Sandel

Miller

Mitani

et al. 2016

Journal of Human Evolution

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Phylogenetic comparative methods have become standard for investigating evolutionary hypotheses, including in studies of human evolution. While these methods account for the non-independence of trait data due to phylogeny, they often fail to consider intraspecific variation, which may lead to biased or erroneous results. We assessed the degree to which intraspecific variation impacts the results of comparative analyses by investigating the “social brain” hypothesis, which has provided a framework for explaining complex cognition and large brains in humans. This hypothesis suggests that group life imposes a cognitive challenge, with species living in larger social groups having comparably larger neocortex ratios than those living in smaller groups. Primates, however, vary considerably in group size within species, a fact that has been ignored in previous analyses. When within-species variation in group size is high, the common practice of using a mean value to represent the species may be inappropriate. We conducted regression and resampling analyses to ascertain whether the relationship between neocortex ratio and group size across primate species persists after controlling for within-species variation in group size. We found that in a sample of 23 primates, 70% of the variation in group size was due to between-species variation. Controlling for within-species variation in group size did not affect the results of phylogenetic analyses, which continued to show a positive relationship between neocortex ratio and group size. Analyses restricted to non-monogamous primates revealed considerable intraspecific variation in group size, but the positive association between neocortex ratio and group size remained even after controlling for within-species variation in group size. Our findings suggest that the relationship between neocortex size and group size in primates is robust. In addition, our methods and associated computer code provide a way to assess and account for intraspecific variation in other comparative analyses of primate evolution.

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A neonatal perspective on Homo erectus brain growth

Cited by 31 publications

References 49 publications

Human Social Evolution: Self-Domestication or Self-Control?

Human Social Evolution: Self-Domestication or Self-Control?

Effects of cranial integration on hominid endocranial shape

Assessing sources of error in comparative analyses of primate behavior: Intraspecific variation in group size and the social brain hypothesis

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