Brain evolution involves changes in size and morphology, but also changes in the capacity to be changed. Plasticity refers to the range of phenotypic variation allowed within a given genetic structure. Environment is a major factor influencing the phenotypic expression, and we humans have a special additional environmental component called “culture”. The ecological, cultural, and social niches, shape each others, with dynamics which are far from being understood. Aida Gómez-Robles and colleagues have now published a morphological analysis of human and chimp brain, taking into consideration heritability. In both species cranial capacity is highly heritable, more for humans than for chimps. Also the general dimensions of the main brain areas show in both species an apparent genetic component. The situation is different when dealing with sulcal morphology, which are still heritable for chimps but not that much for humans. This means that brain morphology in chimps has a stricter genetic program, while humans are more sensitive to non-genetic factors and individual responses. Environmental influences are supposed to be the key, mostly when considering the altricial condition and heterochronic changes associated with the human brain growth and development. In a recent review on the evolution of visuospatial integration with Atsushi Iriki we focused on the necessity to understand to what extent brain changes associated with human evolution are due to genetic, epigenetic or environmental factors. We pointed to the sensitivity of the brain to be “trained” through feedbacks between biology and culture as a crucial variable targeted by selection. This new study stresses further the possibility that selection can act on the capacity to change, more than on the change itself.
Posts Tagged 'brain size'
Tags: brain size, heritability, phenotypic plasticity, sulcal patterns
Tags: brain growth, brain size, encephalization
Christoph Zollikofer and Marcia Ponce de León have published a review on human evolution and endocasts: Pandora’s Growing Box. The article provides comments on topics mostly related to brain size, brain growth, encephalization, cranial evolution, and comparative neuroscience. There are useful notes and images on the correspondence between brain and endocast.
Tags: brain size, isotropic fractionator, neurons
After giving (too) much importance to brain size for more than one century, we are now focusing our attention on functions, parts, and relationships. Nonetheless, the many recent papers by Suzana Herculano-Houzel stress that size matters, indeed. More than size per se, what is definitely relevant is the number of neurons. The number of “computational units” in mammals, primates, or hominids, is incredibly correlated to many biological factors. Patterns are amazingly constant, and linear. After estimations on the number of neurons in fossil hominids, now a recent paper considers the relationships between brain size, metabolism, and foraging. The models developed by using the available information on primates strongly support the theory that the human genus could have had the possibility to increase brain size only thank to food preparation. Otherwise, we should spend all the day searching for something to eat, to maintain such a brain budget!