The most common explanations for such gaps have focused on differences in academic aptitude and preparation, which explicitly or implicitly assume a view of intellectual performance as relatively fixed or slow to change. (scientificamerican.com)
Although that is the most common explanation given, there is no scientific evidence to support this theory. (homevet.com)
In times past those were common explanations from folks like you so desperate for an explanation they just made one up and decided to believe it. (religion.blogs.cnn.com)