Monday, September 21, 2015

Why Aren’t Beavers Intelligent?

Is the evolution of intelligence rare, in the sense that only a very unique and specific set of circumstances could cause it? If it is, then perhaps intelligence is the Great Filter that prevents aliens from visiting Earth. If all the planets that are habitable are full of non-intelligent species, then the only answer to the no-alien question is intelligence.

In a previous post, there was a discussion about how communication and tool-making were the principal evolutionary advantages that intelligence first provides. These two things, perchance, are the ones which cause certain species to rise up out of the average situation, and begin to think conceptually. This has only happened once on Earth, as far as we know, and if we do not draw the line for intelligence too low. However, there are some very clever mammals here on Earth, with one of the foremost being the beaver, and the question is, why hasn’t the beaver, or something else other than a particular primate, developed intelligence?

Beavers are very likely candidates for evolution into intelligent creatures from one standpoint. They are nicknamed, ‘Nature’s engineers’. Beavers are responsible for changing the landscape of wherever they live, back in the days before they were exterminated for their fur by humans. Beavers build dams, which impound water, creating ponds. The ponds change the habitat of the surrounding area, by providing an area for fish to live, for wild life to drink in times of drought or dry seasons, for plants which require nearby water to thrive, for other water-living mammals, such as otters, to live, and much more. As part of the dam, they build a burrow, with typically several underwater entrances. They stock edible branches underwater to survive a winter, even in areas where the stream they engineered freezes over. The burrows provide habitat for several other species, so they can survive in the winter.

There is a tremendous difference between an area with a stream that has not had any beavers for a few decades, and one in which beavers have had free play. The stream will be subject to drying up in a drought, but because beavers also dredge channels as well as build dams, there will be water lasting through the drought. Dams might be built every few hundred meters in a stream with enough vertical drop, which means that there will be less velocity to the water, except where the overflow of the dam is, and therefore less erosion and less soil carried downstream. Because of the silt collection upstream of the dams, the land will have excellent soil conditions after the stream changes its course and leaves the old course free of water flow.

Beavers accomplish this by knawing down trees, up to 12 inches in diameter, and hauling them both across land and through the water to the lodge and dam. They use their forepaws to hold the branches and trees that have been cut. They also use their forepaws to scoop up mud from the bottom of the pond to provide waterproof layers for the dam.

Beavers communicate their dam-building skills to the younger generation. Typically the second year of a beaver's life is devoted to apprenticeship at the side of their father; then they depart to build their own lodge. Thus, they have rudimentary use of their limbs for construction activities, and can teach skills that are not genetically transmitted. Why didn’t they complete the task of becoming intelligent? Beavers have been building dams in much the same way for twenty million years. This is more than enough time to grow a larger brain and to break through the twin barriers between everything else and intelligent creatures.

The answer seems to lie in the details. Beavers are rodents, and have not developed grasping paws. Their paws remain clawed. They do not climb trees, they only cut them down. In a previous blog, it was noted that trees might be a Great Filter, as without them, there might be no evolution of hands, with or without opposable thumbs. Well, beavers certainly have trees, but they live in lodges, and climbing into a tree would be counter to their normal means of survival. Monkeys and some other primates can escape ground-traveling predators by taking to the trees, where they can travel from one to another in dense forests. Predators need to maintain an ability for speed, and this is opposed to having nimble tree-climbing abilities, at least for larger ones.

Thus, using their forelimbs for carrying and pushing trees into place and so on does not translate into a evolutionary advantage for growing fingers instead of claws. It may be further down that line in that beavers do not inhabit areas of Africa where the basic evolution of intelligence occurred, and so did not experience the same environment that drove tree-climbing and hands.

They also communicate, and in two ways. One is the warning signal that beavers give when a predator is seen. This is a tailslap against the water surface. This sends a noise both underwater and through the air, so any beaver within some distance would be able to hear and recognize it, and take immediate action to preserve themselves. Beavers have great breath-holding abilities, but it is hard to see how vocalization could occur underwater with the same type of apparatus as it would occur in the air. Whales and dolphins can certainly vocalize underwater, but not well on land. The types of sound are different. The other type of communication is through gesture and example. This is used for tutelage. The part of the brain that recognizes physical motion and enables imitation of it is not connected with the part that makes vocal sounds. It is true that some systems of communication for deaf people, e.g., sign language, are very rich in capability, but there is no obvious advantage to be gained for a beaver to master symbolic communication. Thus, the second avenue for intelligence, communication of something as simple as a noun-verb combination, is blocked.

What we are approaching here is a slightly better understanding of why intelligence has not occurred multiple times on Earth, and why it might not have occurred on alien planets. Of all the environments that have existed on Earth over the last several million years, only the African savannah provided the right environment for intelligence to spring up. If other planets have not had any long period with this type of environment, they could very well be of the type surmised at the beginning of this blog: nothing but non-intelligent life running around.

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