What do you think about when pondering the intellectual capacity of brains in other species? An article in Scientific American discusses how the brain of a Sperm Whale is larger than the brain of a Human; it is nearly five times the size of ours. Does size reflect intellectual capacity? Or, is it the complexity of the brain's structure? If it's complexity, how might you go about making judgments; perhaps through tests that might reflect activity or firing of neurons? hmmm.
I have thought on this significantly prior to reading this article . and have independently come to the conclusion that different species have different types of intelligence. Whereas our intelligence has lead to advances in our social applications; like communication and expression and we have the biological ability of fine motor skills; I think that other species have abilities and strengths that we lack. I certainly witness intellectual capacity in my two cats that after some affiliation is obvious. It is apparent in other species as well; like Elephants, Big Cats, Bears and Monkeys. Dogs have a social intelligence factor as well, in my opinion, in their abilities to interact so successfully.
But, past the assumptions and on to the facts; there are different ratios to take into account in this thought process; absolute size (or weight) and brain size vs. body size ratios. "The lemming. (Kicrostonyx groenlandicus), for example, has a higher ratio than man." American Naturalist. And, "The brain of a sperm whale is about 60% larger in absolute mass than that of an elephant. Furthermore, the brains of toothed whales and dolphins are significantly larger than those of any nonhuman primates and are second only to human brains when measured with respect to body size." Plos one.
Then there is circumstance; "Brain tissue, which is metabolically expensive, requires constant high levels of oxygen and glucose, regardless of the state of mental activity (Sokoloff 1981). Hofman (1983) determined that the proportion of metabolic expenditure required by the brain relative to that of the rest of the body is generally less than 10%... Hofman (1983), like Robin (1973), suggested that large-brained species have relatively shorter dive times than small-brained divers." The American Naturalist. However, the following line is the important one as I can see it, "Superficially, this conclusion seems obvious; however, it does not consider the possibility that other adaptations to the aquatic environment have taken place." The American Naturalist.
So, here we see claims of size disparity due to the 'needs' of the brain in order to function. These needs are oxygen and glucose and seem to be a reasonable explanation as to why different brain sizes exist in aquatic species. But, alas, this is all disproved by analysis of varying species including the sperm whale, manatee and pinnipeds . This additional analysis showed that some species had longer dive times, while still harboring larger brains.
So, though this last part gains ground more in the environmental factor's of brain size and less in measurement of intelligence; the purpose of it's mention is to prime the mind for such affects.
Interestingly, the sperm whales brain comes in at an impressive 8,000 cubic centimeters; whereas human brains are about 1,300 cubic centimeters. Now, although we mention the Lemming above, Scientific American states that it is the Tree Shrew .~ as one is far more current than the other… I presume they are more likely correct; as is stated here "Porpoises and elephants, fellow mammals known for their extraordinary mental abilities, also have bigger brains than we humans. But that's not fair. Those animals are humongous. You need to take into account brain-to-body size. When that is done, the winner is.. well, the tree shrew, followed by humans and then porpoises." Scientific American.
So, here we see again, proof that the brain-to-body size is not relevant, nor is the absolute weight or size. So, we must dive deeper. "Nina Eriksen and Bente Pakkenberg of the University of Copenhagen take the investigation of whale intelligence to the microscopic level and ask a simply question: If the whale brain is so much bigger than the human brain, does this mean it has more neurons?" From " Total Neocortical Cell Number in the Mysticete Brain " "Logically, brain function and intelligence must relate to the number of neurons. Intelligence resides in neocortex (the thin, convoluted "rind" of the brain_ rather than in other, underlying areas devoted to controlling vital housekeeping functions for the body… The frontal lobes of the dolphin brain are comparatively smaller than in other mammals, but the researchers found that the neocortex of the Minke whale was surprisingly thick. The whale neocortex is thicker than that of other mammals and roughly equal to that of humans (2.63 mm). However, the layered structure of the whale neocortex is known to be simpler than that of humans and most other mammals. In particular, whales lack cortical layer IV, and thus have five neocortical layers to humankind's six. This means that the wiring of connections into and out of the neocortex is much different in whales than in other mammals." Now, we are getting somewhere!
The results of this investigation was that the Minke whale had a total number of 12.8 billion neocortical neurons; 13 times that of the rhesus monkey and 500 times that of rates; whereas it was only 2/3 that of the human neocortex.
So, here we come to another groundbreaker; we can simply measure the neocortex of each species to get a somewhat effective judgment. But alas, there's more, called Glia . Glia are non neuronal cells whose purpose is support of nutrition and signal transmission in the nervous system among other things. Further into Eriksen and Pakkenbergs' studies, they find that there were 98.2 billion non neuronal cells, called glia, in the Minke whale neocortex. This is the highest number of glial cells in neocortex seen in any mammal studied to date. The ratio of neocortical glial cells to neocortical neurons is 7.7 to 1 in Minke whales and only 1.4 to 1 in humans. So, now we are getting where I thought it to be all along.
So, there are different constructions of brains, presumably due to circumstance or environmental factors as well as evolutionary need. The true question to ponder is; in what way do other species minds think? What do they think of us, when we harpoon their families or sell their friends as bush meat? What do they feel emotionally?
No, whale's are not able to paint like Picasso; but, they might be able to think in ways that we have yet to discover and may never completely understand. Shouldn't we allow their survival so as to contribute towards the wonders of intelligence and the value of intelligence among other species…
KAS
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