Here's a review which seeks to reconcile current information about the biology intelligence with the extensive psychological literature that precedes it. Intelligence appears to be influenced by nature (genetics) as well as nurture (environment).
Biological studies are still limited by the need to use controllable, well-circumscribed problems or puzzles (rather than, say life's work or real-life problems solved over the course of years), but there's no doubt that functional imaging has helped scientists elucidate different components of high-level thinking, and there's a much great awareness of how effective thinkers are able to coordinate multiple brain activities well.
There are interesting little tidbits in the review, like "After birth, the environment in which a child is raised also affects their intellectual function. Bouchard et al found that growing up in the same famil increased IQ similarities for all types of relatives..Adopted children's IQs are also correlated with those of their adoptive siblings (0.34) and adoptive parents (0.19). So 20-35% of the observed population differences in IQ are thought to be due to differences between family environments."
Neurobiology of Intelligence
Eide Neurolearning Blog: Who is Smart?
Eide Neurolearning Blog: Parietal Prodigies