How far back can a line go?

How far back can a line go?

A grandfather in Kota Bharu keeps a faded photo of his own grandfather. It is the oldest picture the family owns. Beyond that, the family has only names and stories, and after four or five generations even the names stop.

The story

Most family histories reach back a few generations. Mathieson and Scally (2020) point out that few of us know our family beyond a handful of generations. Paper trails run out when the records do.

DNA keeps a longer record, but only along certain paths. Your mother line is a single chain: your mother's mother's mother, and so on. Mitochondrial DNA passes down this chain almost unchanged. In 1987, three scientists studied the mitochondrial DNA of 147 people from five regions of the world. All of it traced back to one woman, who they thought lived about 200,000 years ago, probably in Africa. Later work has refined this, and in 2012 a team used 8,216 modern mitochondrial genomes to rebuild the tree.

Our family-line stories speak of a woman who "walked out of Africa more than 50,000 years ago". That is the time when branches spread to Asia. A mother line like B4 or a father line like O-M324 shows a small part of that long journey, from Africa along the coasts of Asia to southern China and Southeast Asia.

The two lines are special, because each is a single path. The mother line follows only mothers. The father line follows only fathers. Everything else in your family tree, hundreds and thousands of other ancestors, is not on those paths.

Where you can still see it today

• In the age your family-line story gives for your line, such as "more than 50,000 years".
• In the gap between that age and your family's papers: tens of thousands of years of silence in the records, bridged by the DNA.
• In a family photo album: a few generations of faces, and behind them a line that goes back much further.

What DNA can tell, and what it cannot

DNA can tell you that your mother line, or your father line, belongs to a branch that began long ago, and where that branch was common.

It cannot tell you the names, faces or stories of the people on the line. It cannot say which village your family came from, nor whether one great-great-grandmother was a farmer or a trader. And it follows only two of your many family lines. For the rest, see "How many ancestors do you really have?".

DNA does not decide race, religion or bumiputera status. It also does not give anyone a "pure" or "special" line. Every person alive has a mother line, and every man a Y father line, and they go back just as far for all of us.