The traditional method since the Middle Ages of summarizing and displaying information about the ancestors of an individual. The earliest ones show the first known ancestor at the root or trunk of a tree, with his descendants on the branches, but it soon became the custom to reverse the image by showing descendants below the earliest known member. A modern method is to lay out the information horizontally with a chronological progression from left to right. A wide variety of computer programs are available for both PCs and Macs. The early family trees sometimes make spurious claims about the antiquity of a line. They are frequently casual, or totally uninterested, in following the descendants of the women and of younger sons.
Most families cannot prove continuous descent beyond the 16th or 17th century because of the lack of records. The information that has been gathered is so varied that family trees have to be tailored to meet individual requirements. They are merely summaries which should be fully supported by references to the evidence on which they are based. A modern method is to name only the parents, going back four generations to the sixteen great‐great‐grandparents. The lack of adequate space to include all members of a family means that various overlapping trees have to be constructed. It is advisable to try to keep all those of a particular generation on the same level. See the standard abbreviations which are used.