Ancestor
Overview
An ancestor is a parent
or (recursively
) the parent of an ancestor (i.e., a grandparent
, great-grandparent, great-great-grandparent, and so forth).
Two individuals have a genetic
relationship if one is the ancestor of the other, or if they share a common ancestor. In evolution
ary theory, species which share an evolutionary ancestor are said to be of common descent
. However, this concept of ancestry does not apply to some bacteria
and other organisms capable of horizontal gene transfer
.
Assuming that all of an individual's ancestors are otherwise unrelated to each other, that individual has 2n ancestors in the nth generation before him and a total of about 2g+1 ancestors in the g generations before him.
Parent
A parent is a caretaker of the offspring in their own species. In humans, a parent is of a child . Children can have one or more parents, but they must have two biological parents. Biological parents consist of the male who sired the child and the female who gave birth to the child...
or (recursively
Recursion
Recursion is the process of repeating items in a self-similar way. For instance, when the surfaces of two mirrors are exactly parallel with each other the nested images that occur are a form of infinite recursion. The term has a variety of meanings specific to a variety of disciplines ranging from...
) the parent of an ancestor (i.e., a grandparent
Grandparent
Grandparents are the parents of a person's own parent, whether that be a father or a mother. Every sexually-reproducing creature who is not a genetic chimera has a maximum of four genetic grandparents, eight genetic great-grandparents, sixteen genetic great-great-grandparents, etc...
, great-grandparent, great-great-grandparent, and so forth).
Two individuals have a genetic
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
relationship if one is the ancestor of the other, or if they share a common ancestor. In evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
ary theory, species which share an evolutionary ancestor are said to be of common descent
Common descent
In evolutionary biology, a group of organisms share common descent if they have a common ancestor. There is strong quantitative support for the theory that all living organisms on Earth are descended from a common ancestor....
. However, this concept of ancestry does not apply to some bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...
and other organisms capable of horizontal gene transfer
Horizontal gene transfer
Horizontal gene transfer , also lateral gene transfer , is any process in which an organism incorporates genetic material from another organism without being the offspring of that organism...
.
Assuming that all of an individual's ancestors are otherwise unrelated to each other, that individual has 2n ancestors in the nth generation before him and a total of about 2g+1 ancestors in the g generations before him.
