Once a man called John Smith decided to trace his family tree. He knew nothing about genealogy but had a credit card which brought a subscription to a popular website with templates to populate. He could remember where and when he was born and knew details of his immediate family. Beyond that he was reliant on the records that the system recommended. There were hundreds, waiting to be carefully checked but John did not have time for that.

Many other people called Smith had already built their family trees on the website. Some did not make them confidential, so John was allowed full access. Delighted that someone had done the hard work for him, he exported the data and soon had a complete tree going back two centuries. Proudly he emailed it to all his surviving relatives.

Within minutes he was bombarded with replies about dates and names being incorrect and questions asking how it was possible for ancestors to marry before they were born and to give birth in different countries at the same time.  John didn’t understand the errors, so he blamed the website and cancelled his subscription. His tree remains online to confuse serious researchers.