A feast for the eyes!

Study shows strong correlation between brain size and maternal investment.The longer the pregnancy and breast-feeding lasts, the bigger the species' average brain size and the longer they live, the researchers say.The study looked at the average pregnancy term, breast-feeding length and brain size of 128 species of mammals. They saw that between different species brain size at birth was determined by the length of pregnancy, while the brain growth after birth was determined by breast-feeding duration.Other life-history theories had speculated that large brains increase life span because of the increased intelligence that comes along with it. Instead, the new study shows that the link lies between the extra cost in time and energy invested by the mother and the development of large brains increases the life span of these species.For example, the killer whale has one of the longest pregnancies at 15 months and breast-feeds offspring for another 18 months. Their brains can reach over 300 cubic inches (5,000 cubic centimeters), or about the size of a mini-keg of beer. This extended period also leaves more time for learning and play."The link is all to do with the cost of growing a large brain, and not so much with the benefit of having a large brain," Barton said. "Chimps and other great apes have pretty protracted periods of development and pretty large brains.