Folklorist Alan Dundes pointed out the broad appeal of the number three in American culture. In sports, in humor, and even in the Internet (think WWW), we tend to think in threes.
The same goes for the manuscripts and grant proposals I review. I often see sentences that include lists of three. No matter the topic, the tripartite serial fulfills some language euphony. When writing lists, I favor placing a comma before the “and.” This punctuation is known as the Oxford comma after Oxford University Press, whose style guide recommends it.
Like so many other rules of grammar, the Oxford comma seems to be disappearing. The trend in writing is to pare down punctuation. Some have even suggested that “I” will no longer be capitalized in a future where text message is the primary form of communication.
When I see lists in manuscripts, I don’t impose the Oxford comma, but I do check for consistency in style. In my own writing, I favor the comma before the “and.” As the book Eats Shoots and Leaves makes clear by its title reference to a joke about a panda, the Oxford comma makes meaning more clear.