Colibri:
Personally, I suspect that human intelligence is actually a social adaptation, rather than simply one to deal with the physical environment. Other animals are able to deal with predators, finding food, migrating, etc. just fine without the need for such a large brain. Our intelligence and memory enables us to keep track of the many reciprocal relationships among the members of the group - who helped us out in the past, who we owe favors to, and, perhaps most important of all, to tell when other members of the group are lying to us. Increasing human intelligence has been the result of an “arms race” directed at dealing with other humans, not the environment.
Those skills, however, aren’t unique to us.
From my link below:
Palomar Department Of Physical Anthropology:
The connection between social skills and intelligence can be seen in chimpanzee communities. Success for an individual usually requires that he or she has the ability to learn from others, invent new behaviors, comprehend the status and complex emotions of all other troop members, and can use this knowledge to gain advantages. Chimpanzees learn how to influence and even manipulate the emotions of others. Adult males in particular become experts at bluff, deception, and intrigue. They are often scheming political animals who spend much of their time creating and maintaining alliances with other males. In order to succeed, they need to be “chess masters” of their social worlds. The ability to predict combined effects of yours and other’s actions and to control your own emotions and behavior may be among the most important characteristics that led to the large ape brain. Ultimately, it may have led to the even larger and more intelligent human brain.
I tend to think that our intelligence stems from secondary developments of those social adaptations you mention, namely the capactiy for advanced verbal commuication, and perhaps more importantly, written language.
Think about it MD. If there was such a scientific answer, then the religions today would change or disappear completely, unless people did not accept the scientific reasoning for humans to be smarter than the next living creature.