Here are some extracts from a recent paper by James Hartle and Mark Srednicki at arXiv.org. So, if we’re not typical, are we special? And is our specialness more than just having big brains and being successful at passing on our genes?
ABSTRACT: Bayesian probability theory is used to analyze the oft-made assumption that humans are typical observers in the universe. Some theoretical calculations make the selection fallacy that we are randomly chosen from a class of objects by some physical process, despite the absence of any evidence for such a process, or any observational evidence favoring our typicality. It is possible to favor theories in which we are typical by appropriately choosing their prior probabilities, but such assumptions should be made explicit to avoid confusion.
To compute likelihoods as though we had been randomly selected by some physical process, when there is no evidence for such a process, commits what might be called the selection fallacy. We are not a disembodied entity that was randomly selected to have a particular physical description; instead, we are the meaning of a transcription of Ã¢â‚¬ËœweÃ¢â‚¬â„¢ into the language of physical theory….
At present, there are no observational data supporting an assumption that we are typical in some class of observers, and our understanding of biological evolution is insufficient to supply a theoretical justification through the likelihoods. Many calculations that produce likelihoods that favor our typicality do so via the selection fallacy; this can lead to absurd conclusions….