How Close Are We? The Science of Human Relatedness

Have you ever wondered if you are related to someone you meet on the street, or a celebrity you admire, or even a historical figure you learned about in school? The answer is yes, you are. But how closely are you related, and how can you find out?

The Concept of Relatedness

Relatedness is a measure of how much genetic material two individuals share. The more genes they have in common, the more related they are. The most related people are identical twins, who share 100% of their genes. The least related people are those who have no common ancestors at all, which is very rare.

The degree of relatedness between two people can be calculated using a formula that takes into account the number of generations that separate them from their most recent common ancestor (MRCA). For example, siblings are 50% related, because they share one parent. First cousins are 12.5% related, because they share one grandparent. Second cousins are 3.125% related, because they share one great-grandparent, and so on.

The History of Human Migration

The history of human migration is the story of how our ancestors spread across the globe, intermingled with other groups, and formed different populations. This process has shaped the genetic diversity and relatedness of humans today.

According to genetic evidence, all modern humans can trace their ancestry back to a small group of people who lived in Africa about 200,000 years ago. These people are the MRCA of all living humans. About 70,000 years ago, some of them left Africa and migrated to other continents, where they encountered and mixed with other ancient human species, such as Neanderthals and Denisovans. Over time, these groups adapted to different environments and developed distinct physical and cultural traits.

Today, there are about 7.9 billion people in the world, belonging to various ethnicities, races, and nations. However, despite the apparent differences, we are all genetically very similar. According to a study by the Genographic Project, the average genetic difference between two random individuals is only 0.1%. That means we share 99.9% of our DNA with every other human on the planet.

The Tools of Genealogy

Genealogy is the study of family history and ancestry. It can help us discover our roots, trace our lineage, and find our relatives. There are many tools and methods that genealogists use to research and document their family trees.

One of the most popular tools is DNA testing. DNA testing can reveal information about our ethnicity, haplogroups, and genetic matches. Ethnicity estimates show the geographic regions where our ancestors came from. Haplogroups show the ancient branches of our paternal and maternal lineages. Genetic matches show the people who share segments of DNA with us, and how closely they are related.

Another tool is online databases. Online databases contain millions of records, such as birth certificates, marriage licenses, death certificates, census data, immigration records, military records, and more. These records can provide names, dates, places, and other details about our ancestors and relatives. Some of the most popular online databases are Ancestry, FamilySearch, MyHeritage, and Findmypast.

A third tool is social media. Social media platforms, such as Facebook, Twitter, Instagram, and LinkedIn, can help us connect with our living relatives, share photos and stories, and join groups and communities of interest. Social media can also help us find distant cousins who may have valuable information or documents about our family history.

The Benefits of Knowing Our Relatives

Knowing our relatives can have many benefits, both personal and social. Some of the benefits are:

  • It can give us a sense of identity and belonging. Knowing where we come from and who we are related to can help us understand ourselves better and appreciate our heritage and culture.
  • It can enrich our lives and relationships. Knowing our relatives can help us discover new family members, reconnect with old ones, and strengthen our bonds with them. It can also help us learn from their experiences, wisdom, and values.
  • It can improve our health and well-being. Knowing our relatives can help us identify and prevent potential health risks, such as inherited diseases, allergies, and sensitivities. It can also help us cope with stress, trauma, and grief, by providing emotional support and comfort.
  • It can inspire us and others. Knowing our relatives can help us discover and celebrate their achievements, contributions, and legacy. It can also motivate us to pursue our own goals and dreams, and to make a positive difference in the world.


Is everyone related to each other? The answer is yes, we are. We are all part of one big human family, with a common origin and a shared destiny. By knowing our relatives, we can enrich our lives, improve our health, and inspire ourselves and others. We can also appreciate the diversity and unity of humanity, and foster a culture of respect, tolerance, and peace.