…are apparently smarter than previously believed. They still don’t seem sentient, I think, but they are far more intelligent than their brain-to-body-mass ratio had scientists believe.
Far from being slow learners, manatees, it turns out, are as adept at experimental tasks as dolphins, though they are slower-moving and, having no taste for fish, more difficult to motivate. They have a highly developed sense of touch, mediated by thick hairs called vibrissae that adorn not just the face, as in other mammals, but the entire body, according to the researchers’ recent work.
The entire article is worth reading, but for those of you who are too lazy or can’t access even the blog-friendly NYTimes articles for some reason, there are several crucial snippets, some of which have implications concerning my last dolphin post.
The smooth surface of the manatee’s brain — it generally has only one main vertical fissure, or sulcus, and no surface ridges to speak of — is more puzzling, Dr. Reep concedes. The brains of virtually every other mammal bigger than a small rodent show some degree of folding. And scientists have generally taken the human cortex, a study in ridges and crevasses, as a model of higher-order mental process, assuming accordingly that brain convolution is a sign of intelligence.
“I would make a guess that if you showed a manatee brain to a modern neuroscientist, to this day, most would consider that the manatee is not very smart, that idea is so ingrained,” Dr. Reep said.
But he added that scientists still know almost nothing about what drives the development of brain formation. Evolutionary lineage appears to have an influence. The brains of primates tend to have different patterns of convolution than those of carnivores, for example. And mechanical factors like brain size and the denseness of neural tissue in the cortex may play a role.
Basically, manatees evolved a low brain-to-body-mass ratio because they simply enlarged in order to provide insulation from the water and digest food more efficiently. A similar effect applies to dolphins, 20% of whose body mass is blubber, but it’s apparently far stronger in manatees.
On the other hand, I do have to take exception to the idea that the lack of prey and predators helps manatees keep intelligent. Basic body functions, such as regulating motion and detecting hunger, are something basal that intelligence is built on top of. Hunting and avoiding prey are integrated into higher cognitive functions, so removing them doesn’t remove the need to have extra brain mass.
Certainly part of human intelligence derives from our instincts as hunters and hunted. Since some of the most ingenious inventions – the bow and arrow come to mind – are based on hunting, it’s safe to assume that without the need to predate and avoid being eaten, and more importantly without the brain functions involving that need, we’d be significantly less smart.
If the manatee has high intelligence, it must have skills that are roughly analogous to hunting and avoiding being preyed on, or at least equal in complexity. For instance, it might have very good foraging skills, or have a large brain section devoted to analyzing touch (what’s the Latinate word for that anyway?). But these would likely require many neurons, synapses, and axons, which could easily be more than it actually has.