Brain size, life history, and metabolism at the marsupial/placental dichotomy

Weisbecker, V. and Goswami, A. (2010) Brain size, life history, and metabolism at the marsupial/placental dichotomy. Proceedings of the National Academy of Sciences of the United States of America, 107 (37). pp. 16216-16221. ISSN 0027-8424 Online ISSN 1091-6490 DOI 10.1073/pnas.0906486107

[img] PDF
PNAS-2010-Weisbecker-16216-21.pdf
Restricted to Registered users only

Download (858kB)

Abstract

The evolution of mammalian brain size is directly linked with the evolution of the brain's unique structure and performance. Both maternal life history investment traits and basal metabolic rate (BMR) correlate with relative brain size, but current hypotheses regarding the details of these relationships are based largely on placental mammals. Using encephalization quotients, partial correlation analyses, and bivariate regressions relating brain size to maternal investment times and BMR, we provide a direct quantitative comparison of brain size evolution in marsupials and placentals, whose reproduction and metabolism differ extensively. Our results show that the misconception that marsupials are systematically smaller-brained than placentals is driven by the inclusion of one large-brained placental clade, Primates. Marsupial and placental brain size partial correlations differ in that marsupials lack a partial correlation of BMR with brain size. This contradicts hypotheses stating that the maintenance of relatively larger brains requires higher BMRs. We suggest that a positive BMR–brain size correlation is a placental trait related to the intimate physiological contact between mother and offspring during gestation. Marsupials instead achieve brain sizes comparable to placentals through extended lactation. Comparison with avian brain evolution suggests that placental brain size should be constrained due to placentals’ relative precociality, as has been hypothesized for precocial bird hatchlings. We propose that placentals circumvent this constraint because of their focus on gestation, as opposed to the marsupial emphasis on lactation. Marsupials represent a less constrained condition, demonstrating that hypotheses regarding placental brain size evolution cannot be generalized to all mammals.

Item Type: Article
Uncontrolled Keywords: 2010AREP; IA61;
Subjects: 04 - Palaeobiology
Divisions: 04 - Palaeobiology
Journal or Publication Title: Proceedings of the National Academy of Sciences of the United States of America
Volume: 107
Page Range: pp. 16216-16221
Identification Number: 10.1073/pnas.0906486107
Depositing User: Sarah Humbert
Date Deposited: 21 Sep 2010 10:53
Last Modified: 23 Jul 2013 10:00
URI: http://eprints.esc.cam.ac.uk/id/eprint/1916

Actions (login required)

View Item View Item

About cookies