I participate in several grant review panels each year that cover different areas of biological research. Despite the relatively broad subject areas that they address, such as signal transduction or genomics, I have noticed a strong similarity between many of the proposals I see. They tend to be focused on a few, relatively narrow topics that have been studied for years, and use just a handful of approaches. For example, in the field of signal transduction, it is common to see proposals to investigate the epidermal growth factor receptor (EGFR), but rare to see a study on other types of receptors. Yet the EGFR is the receptor type that we know the most about. A PubMed search on EGFR yields more than 10,000 papers. Repeating the same search for the insulin-like growth factor receptor, however, yields less than 150. There are many other examples.
In short, biological knowledge, like these ...