Brains and a fetus on display at the Whale Museum
The relative sizes of these brains struck me as being significant because it brings into question the claim that humankind holds, of being the most highly evolved species to occupy the Earth. A lot of this claim has been attributed human intelligence. Presumably then, the most easily observed physical form to be presented as evidence for the hierarchy of intelligent life should be the brain.
But if whales and dolphins are known to have larger brains than humans, does that mean that they are more intelligent than humans?
There are a handful of species on Earth that are known to have brains larger than that of a human’s, including the whale, dolphin, and the elephant. The adult sperm whale has a brain size of 8000 cubic centimeters, while the human brain has about 1300 cubic centimeters. Have these animals developed a greater intelligence than humans? Or is brain size in proportion to body size (the encephalization quotient) the deciding factor in the intelligence of a species?
Both hummingbirds and tree shrews are known to have among the biggest encephalization quotient ratios (due in part to their tiny body size) – and yet neither seems to be on even close to a human level of intelligence. Assuming, then, that brain size is a more comparable measure of intelligence than brain to body ratio, what are the causes that led to the growth of brain size in certain organisms over time? The classic example of an early human, the Australopithecus afarensis Lucy, had only a 380 cubic centimeter brain. From an evolutionary standpoint, the human brain grew in size as human language, culture, and society grew more complex over time.
Did whales experience a similar history? The ancestral cetacean (the closest living ancestor is the hippo) had to undergo major transformation of both morphology and behavior in order to adapt into a fully aquatic lifestyle. Did the large brain size of whales develop in response to accommodating these changes? Dr. Lori Marino of Emory University has found that the sudden increase in brain size in whales occurred 10 million years after they fully became aquatic, meaning that their initial adaptation to the aquatic environment was not the main cause behind an increase in brain size. It does seem likely, therefore, that forces behind shaping the whale brain were similar to the ones that shaped the human brain – that after having safely situated themselves in the ocean, the growth of the brain was likely driven by an increasing complexity in social interaction and communication among whales. An example that supports this theory is seen in the fact that toothed whales that cooperate to hunt for food tend to have larger brains than their filter feeding counterparts.
In addition, the whale body plan is more accommodating toward supporting a larger brain. Not only is it supported from all directions by water, it also does not have the constraints of fitting within a pelvis size – necessary for successful childbirth and for walking mobility of humans
But do bigger brains necessarily mean that whales are smarter than humans? It turns out that while brain size matters, it does not account for everything. Whales brains are more convoluted and have a much greater surface area than human brains. In addition, research by Eriksen and Pakkenberg of the University of Copenhagen have shown that the neocortex (where ‘intelligence’ is said to be housed, in contrast to other areas more devoted to the upkeep of vital body functions) of the whale is roughly equal in thickness to that of humans. However, it was also found that the human brain, despite its smaller size, contained more neurons than the brain of a Minke whale. The ratio of glial (non-neuronal) cells to neurons in the neocortex is 7.7 to 1 in Minke whales, and only 1.4 to 1 in humans. While neurons are commonly regarded by humans to be the more important intellectual determinant, can that necessarily prove the intellectual superiority of humans? Can we prove that humans are smarter than whales?
The question of ‘who is smarter than who’ can’t directly be proven by science, because the very definition of intelligence has always been up to subjective debate by not only biologists, but also those involved in the fields of social science. What is intelligence and how do we measure it? One argument is that humans have proven to be the most intelligent species by using tools to manipulate the environment on such a large scale for the benefit of our own species. Since adaptation is the catalyst of evolution, a species that is able to rapidly use its own technology to bridge obstacles is intelligent because it creates its own evolutionary advantage.
However, one could also argue that whales are already so perfectly adapted to their niche (minus human effects) that they don’t need to manipulate or change anything. In addition, their dialects and social structures are either so different or advanced we may never be able to communicate or fully understand them. The auditory input system in whales is more similar to human eyesight than our hearing – being primarily space-oriented, and taking in a lot of simultaneous information. For humans, our hearing is more time-oriented – needing to break down what a whale could convey in a single moment, into more simplified units of sound strung together in temporal sequence. If whales are able to store so much information into sound alone, what need would they have for a writing system in order to communicate or pass down tradition?
There are also key aspects of behavior – previously believed to be exclusive to humans – that have been observed in cetaceans. In terms of tool use, a family of dolphins in Australia has been observed to use sponges as a tool to hunt. Additionally, the bottlenose dolphin has also been shown to meet one of the benchmarks of higher cognition: self recognition (when shown a mirror).
But are these really the correct ways to interpret intelligence? There seem to be more questions raised about this topic than answers. Perhaps the best way to sum up what can be concluded, should be taken from a quotation from Douglas Adams’ So Long, and Thanks for All the Fish:
“It is an important and popular fact that things are not always what they seem. For instance, on the planet Earth, man had always assumed that he was more intelligent than dolphins because he had achieved so much – the wheel, New York, wars and so on – whilst all the dolphins had ever done was muck about in the water having a good time. But conversely, the dolphins had always believed that they were far more intelligent than man – for precisely the same reasons.”
References:
R. Douglas Fields (2008). Are Whales Smarter Than We Are? Scientific American: NewsBlog.
http://www.scientificamerican.com/blog/post.cfm?id=are-whales-smarter-than-we-are
Marino, L, Connor RC, Fordyce RE, Herman LM< Hof PR, et al. (2007) Cetaceans Have Complex Brains for Complex Cognition. PLoS Biol 5(5): e139.
http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0050139
Keim, Brandon. Whales Might Be as Much Like People As Apes Are. Wired Science, June 25, 2009.
http://www.wired.com/wiredscience/2009/06/whalepeople/
Relss, D, Marino, L,. Mirror self-recognition in the bottlenose dolphin: A case of cognitive convergence. PNAS. May 8, 2001 vol 98.
http://www.emory.edu/LIVING_LINKS/pdf_attachments/marino_dolphin_MSR.pdf
Mann J, Sargeant BL, Watson-Capps JJ, Gibson QA, Heithaus MR, et al. (2008) Why Do Dolphins Carry Sponges? PLoS ONE 3(12): e3868.
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0003868