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A family tree is a map of genetically related individuals. Typically, the term is used for a family of humans, but these maps are also widely used by biologists to look at the relationships between various animals. The name comes from the branching nature of a genetic map, which is often drawn to resemble a tree. Genealogists also use them, and they are often provided at the front of biographies and other books about the history of a related group of individuals.
As a visual reference, a family tree is an excellent way to think about the connections between individuals, especially in large families. Historians often create them, especially when they are looking at the history of royal dynasties, to follow the paths of allegiance and relation between various nations. One can illustrate what exactly a second cousin is, for example, or show the precise relationship between an individual and his step-great-aunt. In historical situations where families have tended to intermarry, the tree can sometimes get confusing, and the linear nature is corrupted by lines that appear to sprout in all directions.
In genetics, this type of map can be used to track genetic traits and find the common threads between various animals. It is also an organizational technique, allowing a scientists to arrange animals in common groups, or follow the branches of the animal family from kingdom down to species. Family trees have been used in genetics since the time of Gregor Mendel to help uncover connections that may not be apparent through casual observation. A map can be used to keep everything straight, which can be challenging in some fields of science.
For individual people, a family tree showcases the connections and history of a family. Many people are proud of their relationships to famous historical figures, and are delighted to have a tree illustrating that point. It can serve as a small history lesson of the family, showing the various nations of origin of different members of the family, along with the children they had and when they lived. It can also serve as a memory prompt, because seeing the family member's name can bring out other pieces of the individual's history, such as what he or she did that was distinctive or remarkable.
To construct one, many people work up from themselves as a “trunk” at the bottom of the page. Family connections can be drawn in, starting with parents and siblings. Parents of parents are drawn in, and so forth, until the page is filled with individuals who are related to the trunk in one way or another. Many young students are asked to create a family tree as an interactive exercise to get them excited about history, genetics, and the people of their past.