Long before the internet made this hobby a popular one, I spent many a year on various family history committees. I am in New South Wales, Australia. I share one particular incident. A newbie member asked for help with some early settlers to NSW ... so back in the 1810s. -
We established that her ancestor "John" was in one of the regiments who escorted the convicts to NSW on the transport ships, and his regiment was on rotation. He was a married man, but it did not seem that his wife and family came with him.
We next established that she may have had a child born some 15 months after he had been sent to NSW, and we could find him in NSW across all that time
The newbie then decided that the wife had travelled out to spend time with him and had returned home to have her baby. The newbie was not willing to concede that wife had had a relationship with someone else, afterall, "Once married, you cannot fall pregnant by anyone apart from your husband".
Our volunteer research officer did spend a great deal of time looking at possible shipping opportunities, bearing in mind that 1810s - well err it was a time of sail, trade winds, pre Suez canal etc.
If I recall correctly, we found the baptism for the baby, and there was a middle name that may have pointed to the 'punative' father, and a margin note too
but the newbie did not want to acknowledge any of those aspects.
JM