The spinal cord ratio is considered key. Note how it compares to human. So will dolphins live forever? They have lungs, eyes, and brains. What more is required?
earthtrust.org
"As anyone who has had the opportunity to watch dolphins perform in a show can attest, dolphins have an impressive ability to learn and imitate behaviors, often for what appears the sheer pleasure of doing so. This observation, together with their large brain size, has led to numerous studies of dolphin intelligence. Dolphins' brains are about the size of our own. Size alone, however, is not always a reliable indicator of intelligence. Elephants, for example have brains four times the size of humans, but we do not consider them to be four times as smart! Scientists believe a more accurate factor in determining a species' level of intelligence is the ratio of brain weight to spinal chord weight. In fishes, the brain weighs less than the spinal chord; in cats the ratio is 5:1; in apes, 8:1; in humans, 50:1; and in bottlenose dolphins, about 40:1, suggesting that dolphins have a level of intelligence comparable with humans.
Another characteristic used to determine the level of intelligence is the amount of folding in the cerebral cortex, the portion of the mammalian brain associated with thinking and reasoning. A cerebral cortex which is more deeply folded has a greater surface area available for thinking. Some species of dolphins have brains that are more deeply folded than human brains, although the cortex itself is not as thick. The level of folding in dolphin brains again suggests that they have a level of intelligence comparable to ours." |
