Haplogroups: family trees of mother and father lines

Haplogroups: family trees of mother and father lines

A grandmother in Ipoh pours tea for the whole family on the first day of Chinese New Year. Around her are children, cousins, in-laws. If you drew them all on paper, you would draw a tree. Now imagine a tree so big that it holds every human being alive, and each branch has a name. That is what scientists do with DNA.

The story

Most of your DNA is shuffled in every generation. But two pieces are passed on almost unchanged. One is mitochondrial DNA, which children inherit from their mother (NHGRI). It runs along the mother line. The other is the Y chromosome, which only males carry (NHGRI). It runs along the father line.

Over thousands of years, tiny changes, called SNPs (pronounced "snips"), appear in these pieces. A SNP is a one-letter change at one place in the DNA. People who share the same SNPs share a common ancestor, and scientists give each group a name. That name is a haplogroup. The word means "a group of people who share a common ancestor on the mother line or the father line" (ISOGG).

The names follow a simple pattern. Top-level groups get letters, such as B, M or O. Deeper branches add numbers and more letters, such as B4 or O-M324. For father lines, the name often includes the SNP that marks the branch. Think of a haplogroup as a surname for a very big family, one that is thousands of years old rather than a few hundred.

The tree is kept up to date by researchers. The mother-line tree is at phylotree.org, and in 2012 scientists refined it using the complete mitochondrial DNA of 8,216 people. As more people are tested, new branches appear and old names are tidied.

Where you can still see it today

• In your family-line story, the short name, such as B4 ("The seafarers' line") or O-M324 ("China's most common father line"), is the haplogroup.
• Two relatives who share the same mother line have the same mother-line haplogroup, and two men in the same male line have the same father-line haplogroup.
• Researchers use these names to compare what they find in Malaysia with what they find in other parts of Asia.

What DNA can tell, and what it cannot

A haplogroup can tell you about one line of your family far back in time: your mother's mother's mother, or your father's father's father. It can show where that line probably spent much of its history.

It cannot tell you about your other ancestors. You have many more ancestors than those two lines (see "How many ancestors do you really have?"). It also cannot tell you what you look like, what language you speak or what community you belong to (see "Why a haplogroup is not a nationality").

DNA does not decide race, religion or bumiputera status. A haplogroup is a label for a branch of a family tree. It is not a label for a person.