A family is a group of people related by the ties of blood, marriage, or adoption. Members of a family most often live in a single residence and perform different duties. Members of a family and their duties vary from culture to culture and at different times in history. Who is considered a family member, and what responsibilities that family member has, may depend on their age, sex, and relationship to other family members.

A nuclear family includes a father and a mother, or a single parent, and their children. A nuclear family often lives in a residence separate from other relatives. Nuclear families are one of the most familiar and oldest types of families. They are common in developed countries such as the United States. In many countries with traditions of nuclear families, married couples are expected to move out of their parents homes in order to pursue careers and set up their own household.

A household in which parents, children, grandparents, and other relatives live is known as an extended family. Extended families are important in agricultural societies because they provide a labor force to work a single unit of family land and perform household tasks. An extended family can also provide care for the elderly and young in the household. In India, for example, extended families usually consist of two or more married couples who share finances and a common kitchen. By sharing responsibilities, an extended family is able to support all members of the household both socially and economically.

Clans are another form of an extended family. A clans members typically claim a common relative. Clans unify people who might otherwise be divided by their different places of residence or distinct age groups. Clan members and their allies often provide one another with economic and social support. Clans, sometimes called tribes, are an important part of cultural and political life in Central Asia. Clans such as the Buguu, the Sarybagysh, and the Adygine continue to dominate the politics of Kyrgyzstan, for example.

A family may be led by either a man or a woman. A patriarchal family is one run by the father or eldest male of a household. He usually decides the duties of the women and children in the family. Traditionally in Nigeria, the eldest male is the patriarch, or leader, of the extended family. In this role, the patriarch solves family disputes and divides the familys wealth. The patriarch is also the spiritual leader of the family because he is thought to be the closest to the spirits of the familys ancestors.

A family in which a woman is the head of the household is known as a matriarchal family. The Mosuo people of southwestern China live in matriarchal families. The Mosuo family is made up of matrilineal members, or people who are related to the matriarch, or female family leader. The family would include the grandmother, mother, the mothers sisters and brothers, and the children of the mother and her sisters. Like the patriarchal family in Nigeria, the mother of a Mosuo family is in charge of the households wealth. If there are many sisters in one family, the smartest and most capable sister will be elected the Dabu, or head of household. Unlike most families in the United States, Mosuo couples do not set up a new family and do not share property. Their children are the responsibility of the female partner. The male partner helps raise the children of his sisters.

Genealogy

The study of a familys origins and history is known as genealogy. Your genealogy includes all the people who are related to you across all of history. Your siblings, parents, grandparents, and even your great-great-great grandparents each represent a different generation in this ancestry.

A generation is a set of family members who make up one step, or stage, in your family history. Siblings and cousins are usually in the same generation. Parents are usually a generation older than their children.

Genealogists are scientists who study ancestry and family history. Genealogists often make a list of all of a persons relatives, and then arrange them in a chart that is organized by generation. This chart is known as a family tree. Newer generations are placed at the bottom, or trunk, of the tree. Older generations, or branches, are placed near the top. The chart resembles a tree in shape because the number of family members is often wider at the top than at the bottom.

A family tree uses a number of symbols to define how people are related. Arrows indicate a birth. A parallel line indicates a sibling. An equal sign indicates marriage.

The study of ones family origins has become very popular, and a number of services exist that can help someone trace his or her family history. The Genographic Project, for example, uses advanced technologies to analyze historical patterns in DNA from people around the world. DNA is a material in your cells that stores information about your ancestry. The Genographic Project collects individuals DNA and then runs a test to show maternal or paternal ancestry. By tracing each generations history, the Genographic Project has been able to chart human migration over the course of hundreds of thousands of years.

Changing Families

The structure of families is constantly changing. For example, during the Industrial Revolution, a period of technological change in the 18th and 19th centuries, more women began working outside the home. Before the Industrial Revolution, working outside the home was considered a responsibility for male members of the family. Caring for children was considered a responsibility for female members of the family.

A rise in the number of divorces has led to an increase in the number of stepfamilies. Stepfamilies are families in which one or both members of a couple have children from a previous relationship. The number of one-parent families, where one parent or another adult is the sole provider for their family, has also increased.

A couple or individual parent may also choose to adopt a child. Parents can adopt children who are related to them or are from a different community, or even a different country. The process of adoption is often long and difficult. Families who choose to adopt usually must get permission from government agencies. Same-sex couples, couples with disabilities, and couples from different ethnicities sometimes face prejudice and legal obstacles when looking to adopt.

Animal Families

Animals, much like humans, have different ways of creating and organizing their families.

Penguins create families that are similar to nuclear families. The same male and female penguin couple meets every season to mate and bear offspring. Both penguins take turns incubating the egg and going for food. After birth, the penguin chick is taken care of by its parents until it sheds its fuzzy down feathers. The chick is then able to leave the family in order to search for its own food and mate.

Elephants, on the other hand, live in matriarchal families. Each family is made up of three to 25 adult females and their offspring. The females remain close throughout their lifetimes and help raise all of the baby elephants, called calves. The family is led by an older female who makes all the decisions. Male elephants leave their families between the ages of 12 and 15 and have no long-term bonds with any other elephants.

Some animals have family structures that do not resemble human families. All the honeybees in a single hive are usually related, creating a family with hundreds of members. The matriarch, called the queen bee, is usually the mother of all the bees in the hive. She is the only female that can reproduce. She eats food different from the rest of the bees in the hive. The other female bees, called worker bees, create the honeycomb, take care of the bee larvae, gather food, and make honey. Male bees, called drones, mate with queens from different hives to produce offspring.

Scientific Families

The term family is also used in the studies of biology, chemistry, and math. These definitions of family demonstrate how different sets of information are related.

In biology, the term family describes a group of organisms that come from the same ancestors and share common characteristics. Dogs, wolves, and foxes, for example, are members of the same family, canidae. Much like genealogy, taxonomy is the study of these groups of organisms and their common ancestors. The taxonomy of a certain animal or plant is a chart that describes its ancestry, much like a family tree does for people.

In chemistry, a family is a group of substances that share certain chemical characteristics and have a common name. Sometimes, a family is a group of elements that appears in the same column of the periodic table of elements. The noble gases, for example, are a chemical family that appears in the far right column of the periodic table.

In math, a family is a set of equations using the same numbers. There are usually only three numbers in a simple fact family. One, two, and three are the numbers in the family for the equations 1 2=3, 2 1=3, 3-1=2, and 3-2=1.