Mental retardation in animals Can (something like) mental retardation be observed in animals as well? That is, within an individual species, is there a percentage of individuals who are mentally underdeveloped for their age?
Yes, definitely. Developmental defects of the CNS can occur in any animal with a CNS. But you don’t see them very often as they usually don't live very long in the ultra-competitive wild. But I guess we have to define our terms. What do you mean by the term “mental”? Do you mean brain development in general or higher cognitive functions? The difference between human brains and other animals is the relative size of our cerebral cortex (the outer part of the cerebrum). This is the part of the brain that is (predominantly) associated with cognitive processes. So humans can have a developmental defect (or damage due to acute injury) of the cortex that results in specific impairment of higher cognitive faculties without any impairment of other CNS functions and who are still able to compete and survive on their own. I think it would it would be true to say that this does not occur in other animals (except maybe for other primates) due to other animals not having a developed cortex and such cognitive functions in the first place.<P>
The term "mental retardation" may not be the most appropriate, but I know no other way to put it; for now. I am thinking of the kind of mental retardation that can be observed in the behaviour of an animal -- in comparison to other individuals of his kind and age. For example, I have seen quite a number of cats, and a few stand out. (I know, this is just a speculation based on street observation -- but I hope someone can tell me more.) One of the cats is an orphan and has been abandoned by his owners at the age of about 5 months; he has been adopted by a family in my street, and is now about 2 years old. One immediately notices that the cat is somehow different -- the look in his eyes is stupid, yes, I have no other way to say it. Normally, cats look into one's eyes, but he doesn't. He is uncharacteristically shy (there's plenty of undomesticated cats here which you cannot catch, but they aren't nearly as shy as he). When he came into the neighbourhood, we had him for a while, and he wasn't one bit playful, and he was very clumsy, nothing seemed to interest him. He is now very thin, considering the food the cats get at that house, he is also malnourished -- but the other three cats living there are all fine. I wonder why he is this way. The early trauma that he must have experienced as a kitten certainly left traces on his psyche -- but what kind of damage has been done? Is his odd behaviour of a psychological nature (and could technically be cured with the right nurture) -- or has that early trauma (esp. malnutrition) left damage to his brain, which then results in odd behaviour -- or was he "born with it"?
Sounds like the behavior or attributes of dogs I've known which have been stricken with a stroke or two.
Three types of mental retardation in both humans and probably all animals, but my personal experience is with dogs: delopmental defects of the brain during the embryological stage, especially the cortex as Hercules describes above; mental retardation that occurs as a result of some form of brain injury (stroke, pollution, injestion of a poisonous substance, an trauma accident, concusion/coma, etc.), and mental retardation that occurs as a result of improper environmental effects during development after birth. For example, I once traveled to New Mexico to purchase a 6 month puppy that was referred to be by another breeder. This dog was definitely mentally retarded due to social isolation and lack of both other canine and human interaction.
Christ, I don't have time to look it up but I think that all archaebacteria, i.e., bacteria that live in extreme environments like in deep sea volcanic areas or even in petroleum deposits do not use oxygen (need to say 02, not air - big difference). They produce methane. However, according to earth's geological history, the diversity and abundance of animal and plants evolved in a somewhat proportionate amount equal to the increase of O2 on earth (originally there was no oxygen 02): Cambrian period 543 million years ago 02 levels were approacing the current level: almost all animal classification/diversity (phylums) were present. 600 million years ago 02 level was less than 5% of current level: fauna plant species formed. 1.5 billion years ago 02 level was less than 1% of current level: Eukaryotes (great great great great ancestors to mammals) evolved. 3.8 billion years ago 02 first appeared: origin of life (prokaryotes) About 4.5 billion years ago: origin of eath
