Ancestry.com has about six million DNA samples in its database. In a four-day sale late last year, they sold 1.4 million test kits.

In a short space of time, DNA mapping has raced from being the stuff of rarefied scientific research to an almost do-it-yourself process, achievable with a few decent wads of spit and around $100.

New Zealanders are leaping into the craze too, eager to learn more about their ethnic make-up and possibly discover some previously unknown relatives who have already taken the test.

But it's not all harmless fun. In this Superfad episode, genealogist Gail Wilson-Waring tells us people have been known to get an unwelcome shock about their lineage after seeing their results. And geneticist Dr Kate Neas explains how results that suggest a greater risk of certain diseases may be misleading.

Hosts Laura Walters and Katie Kenny ask: Are we comfortable with private companies holding DNA samples from many millions of people around the world?

Read more about the DNA mapping craze via the Superfad page on Stuff: stuff.co.nz/superfad

And join the Superfad Facebook group to share your thoughts on this trend, and others: https://www.facebook.com/groups/186422305302755/

Katie and Laura are hosting Facebook Live videos each Monday, where they will answer your questions, and take you behind the scenes: https://www.facebook.com/Stuff.co.nz/