Erik Underwood's research project involved the demography of wife/husband pairs, in cases where it was clear from the gravestones that a couple was married. In this chart, husbands (blue dots) are connected to their wives (red dots) by the black lines. The horizontal axis shows each person's year of birth, and the vertical axis shows their age at death. This means that if a husband is older than his wife, the blue dot is to the left of the red dot.

We know from modern demographics that on average a husband is a few years older than his wife. In this sample, that is true in all cases but one. Can you find it? Near the middle of the chart, there is a man who was born around 1865, who died at about the age of 70. He had two wives - the first was a few years older than him, and she died at about the age of 27. He apparently re-married, and his second wife lived to be almost 80.