Abstract
Our large brain, long life span and high fertility are key elements of human evolutionary success and are often thought to have evolved in interplay with tool use, carnivory and hunting. However, the specific impact of carnivory on human evolution, life history and development remains controversial. Here we show in quantitative terms that dietary profile is a key factor influencing time to weaning across a wide taxonomic range of mammals, including humans. In a model encompassing a total of 67 species and genera from 12 mammalian orders, adult brain mass and two dichotomous variables reflecting species differences regarding limb biomechanics and dietary profile, accounted for 75.5%, 10.3% and 3.4% of variance in time to weaning, respectively, together capturing 89.2% of total variance. Crucially, carnivory predicted the time point of early weaning in humans with remarkable precision, yielding a prediction error of less than 5% with a sample of forty-six human natural fertility societies as reference. Hence, carnivory appears to provide both a necessary and sufficient explanation as to why humans wean so much earlier than the great apes. While early weaning is regarded as essentially differentiating the genus Homo from the great apes, its timing seems to be determined by the same limited set of factors in humans as in mammals in general, despite some 90 million years of evolution. Our analysis emphasizes the high degree of similarity of relative time scales in mammalian development and life history across 67 genera from 12 mammalian orders and shows that the impact of carnivory on time to weaning in humans is quantifiable, and critical. Since early weaning yields shorter interbirth intervals and higher rates of reproduction, with profound effects on population dynamics, our findings highlight the emergence of carnivory as a process fundamentally determining human evolution.
Highlights
The evolutionary, ecological, social, behavioral and cognitive implications of the relatively high level of carnivory in humans compared to other extant primates [1] have been the subject of vigorous debates in a variety of research fields over the past fifty years [2], [3], [4], [5], [6], [7], [8], [9], [10]
Data on time to weaning, female body mass, adult brain mass, limb biomechanics and dietary profile from 67 species, representing 67 genera and 12 mammalian orders were included in the analyses
The N-numbers for the different categories with respect to limb biomechanics and dietary profile are presented in the relevant figures
Summary
The evolutionary, ecological, social, behavioral and cognitive implications of the relatively high level of carnivory in humans compared to other extant primates [1] have been the subject of vigorous debates in a variety of research fields over the past fifty years [2], [3], [4], [5], [6], [7], [8], [9], [10]. A ‘significant’ amount of carnivory has been suggested to correspond to a shift from 10% to 20% of food from meat [4]. This shift corresponds to the difference between chimpanzees, with on average around 5% of their diet being meat [1], and tropical populations of hunter-gatherers living in environments similar to those of the African Pliocene, with estimated carnivorous diet of between 20% and 50% [4]. As emphasized by syntheses of large numbers of studies, most of these predictions suggest a substantially later weaning age than practiced by modern humans, in the industrial world [16], and in human natural fertility societies (the latter displaying an average of ca. 27 months [5])
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
