I don't see keeping to oneself as a specifically autistic trait. I know many people who are quite solitary but not autistic, just introverted and socially withdrawn for other reasons. I only get like that when I am anxious or struggling with sensory problems (which has been most of this year, but not the other 40-odd years before that).
Mary Day-Petrano (an autistic savant -- you can Google her) has a particular affinity for horses and she told me that horses actually use certain parts of their brains in a manner similar to the way autistic savants do.
In theory, any kind of mammal could have sensory processing disorder and similarly styled brains to autistic brains in humans. Someone here at WrongPlanet told me a long time ago that research has shown it to be so -- I just wouldn't know where that message is now, so I can't provide any good evidence now, I am afraid.
It depends on how you define autism. Is it certain kinds of stereotypical behaviour, or is it a certain kind of brain (which sometimes produces a variety of behaviours unlike those of neurotypical people)? My autism is what makes me have meltdowns, but it is also what makes me love categorising and systematising. And if I spend several days doing stuff that neurotypical people might also enjoy doing, that doesn't mean I have ceased to be autistic. I was always autistic, and I always will be autistic. When someone tells me, "But you don't LOOK autistic!" (naively intended as a compliment) I sometimes say, "Well, I could always have a meltdown or start flapping or something if you need proof." They expect a certain stereotype. Autism doesn't always look like a wallflower. I speak in public. I dance in front of people. For many years I loved going out in a group.
Does a dog have to freak out and bark obscenely and then fall down exhausted, or line up his bones, or arrange his bedding symmetrically to be called autistic?
They diagnose autism in humans according to behavioural criteria. That's wrong. They should identify autism by using brain tests, only that would be too expensive.
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When I must wait in a queue, I dance. Classified as an aspie with ADHD on 31 March 2009 at the age of 43.