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Allomaternal care, brains and fertility in mammals: who cares matters


Heldstab, Sandra A; Isler, Karin; Burkart, Judith M; van Schaik, Carel P (2019). Allomaternal care, brains and fertility in mammals: who cares matters. Behavioral Ecology and Sociobiology, 73(6):71.

Abstract

The expensive brain hypothesis predicts that the lowest stable level of energy input sets the upper limit to a species’ brain size. This prediction receives comparative support from the effects of experienced seasonality (including hibernation) and diet quality on mammalian brain size. Here, we test another prediction, which concerns the temporal stability of energy inputs. Allomaternal care in mammals can be provided by breeding males or other helpers (usually earlier offspring). Male care should be stable and reliable since otherwise no breeding would occur. Care by others, in contrast, should fluctuate, as the availability of helpers often varies. One would therefore predict, other things being equal, that the presence of male care in addition to maternal care should show positive correlated evolution with brain size, whereas care by others would not. However, because females can readily respond through litter size adjustments to variable amounts of energy inputs, helper inputs may be used to increase fertility. A detailed comparative analysis of a large sample of mammals (N = 478 species) showed that male help is correlated with the evolution of larger brains, whereas alloparental help is correlated with higher fertility, but only in species where male care is also present (as in cooperative breeders). Humans evolved an unusual form of multi-family cooperative breeding, which involves stable and reliable care by both fathers and alloparents. This combination helps to explain why humans differ from the other apes in having both an extremely large brain and a relatively high reproductive output.

Abstract

The expensive brain hypothesis predicts that the lowest stable level of energy input sets the upper limit to a species’ brain size. This prediction receives comparative support from the effects of experienced seasonality (including hibernation) and diet quality on mammalian brain size. Here, we test another prediction, which concerns the temporal stability of energy inputs. Allomaternal care in mammals can be provided by breeding males or other helpers (usually earlier offspring). Male care should be stable and reliable since otherwise no breeding would occur. Care by others, in contrast, should fluctuate, as the availability of helpers often varies. One would therefore predict, other things being equal, that the presence of male care in addition to maternal care should show positive correlated evolution with brain size, whereas care by others would not. However, because females can readily respond through litter size adjustments to variable amounts of energy inputs, helper inputs may be used to increase fertility. A detailed comparative analysis of a large sample of mammals (N = 478 species) showed that male help is correlated with the evolution of larger brains, whereas alloparental help is correlated with higher fertility, but only in species where male care is also present (as in cooperative breeders). Humans evolved an unusual form of multi-family cooperative breeding, which involves stable and reliable care by both fathers and alloparents. This combination helps to explain why humans differ from the other apes in having both an extremely large brain and a relatively high reproductive output.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Department of Anthropology
05 Vetsuisse Faculty > Veterinary Clinic > Department of Small Animals
Dewey Decimal Classification:300 Social sciences, sociology & anthropology
Uncontrolled Keywords:Animal Science and Zoology, Ecology, Evolution, Behavior and Systematics
Language:English
Date:1 June 2019
Deposited On:26 Jun 2019 09:18
Last Modified:17 Sep 2019 20:24
Publisher:Springer
ISSN:0340-5443
OA Status:Closed
Publisher DOI:https://doi.org/10.1007/s00265-019-2684-x

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