An
ancestor is a
parentA 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 (
recursivelyRecursion 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
grandparentGrandparents 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
geneticGenetics , 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
evolutionEvolution 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 descentIn 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
bacteriaBacteria 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 transferHorizontal 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 2
n ancestors in the
nth generation before him and a total of about 2
g+1 ancestors in the
g generations before him. In practice, however, it is clear that the vast majority of ancestors of humans (and indeed any other species) are multiply related (see
Pedigree collapseIn genealogy, pedigree collapse describes how reproduction between two individuals who knowingly or unknowingly share an ancestor causes the number of distinct ancestors in the family tree of their offspring to be smaller than it could otherwise be. Robert C...
). Consider
n = 40: the human species is more than 40 generations old, yet the number 2
40, approximately 10
12 or one trillion, dwarfs the number of humans that have ever lived.
Ignoring the possibility of other inter-relationships (even distant ones) among ancestors, an individual has a total of 2046 ancestors up to the 10th generation, 1024 of which are 10th generation ancestors. With the same assumption, any given person has over a billion 30th generation ancestors (who lived roughly 1000 years ago) and this theoretical number increases past the estimated total population of the world in around AD 1000. (All of these ancestors will have contributed to one's autosomal
DNADeoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
is concerned: this excludes Y-chromosomal DNA and mitochondrial DNA.)
Some cultures confer reverence to ancestors, both living and dead; in contrast, some more youth-oriented cultural contexts display less veneration of elders. In other cultural contexts, some people seek providence from their deceased ancestors; this practice is sometimes known as
ancestor worship or, more accurately,
ancestor veneration.
See also
- Cousin
In kinship terminology, a cousin is a relative with whom one shares one or more common ancestors. The term is rarely used when referring to a relative in one's immediate family where there is a more specific term . The term "blood relative" can be used synonymously and establishes the existence of...
- Ethnicity
- Family
In human context, a family is a group of people affiliated by consanguinity, affinity, or co-residence. In most societies it is the principal institution for the socialization of children...
- Family relationship
- Genealogy
Genealogy is the study of families and the tracing of their lineages and history. Genealogists use oral traditions, historical records, genetic analysis, and other records to obtain information about a family and to demonstrate kinship and pedigrees of its members...
- Kinship
Kinship is a relationship between any entities that share a genealogical origin, through either biological, cultural, or historical descent. And descent groups, lineages, etc. are treated in their own subsections....
- Most recent common ancestor
In genetics, the most recent common ancestor of any set of organisms is the most recent individual from which all organisms in the group are directly descended...