Here's a Comma Doing Good Work

The economist Kenneth Arrow died this week, and in his obituary in the Washington Post, we find, in the following sentence, a comma doing good work:

Dr. Arrow came from a prodigious family of economists that includes his nephew Lawrence H. Summers, president emeritus of Harvard University, former treasury secretary and former director of the White House National Economic Council; and his late brother-in-law Paul A. Samuelson, the first American to win the Nobel Prize in economics, in 1970. 

It's the comma near the very end, before the phrase in 1970. Without the comma, the sentence might mean that Paul Samuelson was the first of two or more Americans to win the Nobel Prize in 1970. With the comma, it makes it clear that Professor Samuelson was the first and only American winner in 1970.

Why is that? Set apart with a comma, in 1970 becomes an incidental piece of information. In other words, it can be deleted from the sentence without impairing the meaning of the sentence:

Dr. Arrow came from a prodigious family of economists that includes his nephew Lawrence H. Summers, president emeritus of Harvard University, former treasury secretary and former director of the White House National Economic Council; and his late brother-in-law Paul A. Samuelson, the first American to win the Nobel Prize in economics.

The important point here is that Professor Arrow's brother-in-law, like Professor Arrow himself, won the Nobel Prize; that he won it in 1970 is purely incidental. 

Unconvinced? Consider the following sentence, which I hope reports an unfamiliar fact:

Ross Barnes of the Chicago White Stockings became the first player to hit a home run in 1876.

What is special about this claim? Was it that Ross Barnes was the first player of many to hit a home run in 1876? Or was it that Ross Barnes was the first player to ever hit a home run, and he did so in 1876? The point is that, without a comma before in 1876, it's hard to tell.

As it turns out, Ross Barnes was the first player to ever hit a home run, and he did so in 1876. We can make that clear by separating in 1876 from the rest of the sentence with a comma:

Ross Barnes of the Chicago White Stockings became the first player to hit a home run, in 1876.