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

• DOI: 10.1073/pnas.0906486107
• Publication Date: 2010-09-08T02:21:32Z
• Authors: Vera Weisbecker; Anjali Goswami
• Keywords: 0301 basic medicine; Placenta; Brain; 612; Altricial; Biological Evolution; Basal metabolic rate; 03 medical and health sciences; Marsupialia; Encephalization; Pregnancy; 1000 General; Animals; Female; Basal Metabolism; Maternal energy hypothesis

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