Andrew Stone goes in search of his ethnic roots with the help of science and a little bit of saliva.

There he is, in a list of distant relatives identified by powerful computers in the United States, a man in Florida who the data suggests is a fourth, fifth or sixth cousin.

The possibility that the smiling chap in the screen shot shares a common relative with me has all come from a sample of saliva put through DNA analysis by Ancestry.com, the world's largest online family history resource.

The DNA results were fed into a database which contains the analysis of hundreds of thousands of other samples to produce a list of possible relatives. None of the 58 matches identified by the system was known to me.

And none of the four I reached out to this week has so far come back to shed light on how we might be related in the interconnected world. The electronic family tree, created through a combination of chemistry and computers, cost $162 plus shipping fees and was produced by Ancestry, the world's largest family history resource.

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Ancestry generates personal ethnicity maps and lists of possible distant relatives. It churns out the more conventional family trees as well, based on digitised birth and marriage registers, censuses, customs records, passenger lists and other databases.

But it's the DNA product, which Ancestry launched in New Zealand this week - after previously rolling out the kits in the US and the UK - which the company is eager to highlight.

The technology, Ancestry says, is based on best-practice science. The privately owned US-based online family history service employs geneticists, mathematicians and software specialists to keep the company ahead of the pack in what is a highly competitive field.

The process takes six to eight weeks and is restricted to family history, unlike DNA paternity tests, or health profiles checking for disease susceptibility. The results posted online from the saliva analysis do not say the 58 individuals which Ancestry's technology found are actual relatives, or whether they are precisely fourth or more distant cousins.

What the site says is that there is a "high", "very high" or "extremely high" level of confidence that the individuals picked up within the company's vast data base share DNA markers which suggest we could share common ancestors - all this from a dribble of spittle.

In the case of 'ddmoss-sr', the Tampa, Florida man which Ancestry's algorithms suggest is a fourth cousin, the level of confidence is "very high". (Fourth cousins share great-great-great grandparents.)

The individual at the top of the list - whose online name is given as Kimberly Poma from Washington in the US - appears with an "extremely high" level of confidence that she is a fourth to sixth cousin.

Looking at her family tree, which can be found on the site, there is no name which leaps out that strikes a chord. But there is in her "ethnicity estimate" a number of regions where her forebears once lived which overlap with my own.

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Kimberly's major ethnic mix covers Britain, Europe West, Ireland, Scandinavia, and 'Native America'. Her DNA also produced traces of Italy/Greece, Senegal, Finland/Northwest Russia and the Iberian Peninsula or modern day Spain and Portugal.

The results of my DNA sample included Britain (58 per cent), Europe West (12 per cent), Scandinavia (11 per cent), traces of the Iberian Peninsula (6 per cent) Europe East (4 per cent), Italy/Greece (4 per cent), Ireland (2 per cent) and Finland/Northwest Russia (2 per cent).

The connection to northern Europe is spot on: my late father's maternal line came from what was once Prussia.

An overlap with 'ddmoss-snr' - whose major ethnic pool centres on West Africa - occurred in Britain. So perhaps one of his British ancestors came in close contact with one of mine, before his relations crossed the Atlantic and mine came Downunder.

Dig a little deeper into the Ancestry site and the connections are couched with conditions.

The company says the DNA predicts that "Kimberly Poma" is "probably your fourth cousin". It acknowledges she could also be "a third cousin once removed, or perhaps a fifth or sixth cousin".

Cautions Ancestry: "For relationships this distant from you, there is greater statistical variation in our prediction. It's most likely to be a fourth cousin type of relationship (which are separated by ten degrees or ten people), but the relationship could range from six to twelve degrees of separation."

At this level of analysis, Ancestry says its model can predict "only about 71 per cent of the possible relatives that are out there - in other words there is a 29 per cent chance that our DNA analysis cannot recognise an actual relative of yours".

To be more certain, the company suggests that more immediate family members provide samples - all for a fee of course.

Ancestry is the biggest of the firms which offer autosomnal DNA tests, a technique which the company says surveys an individual's genome at more than 700,000 locations and covers maternal and paternal sides of the family tree. The company's ethnicity regions includes a broad sweep of Polynesia, which would include people of Maori descent.

Brad Argent, Ancestry's London-based commercial development manager, who was in New Zealand to launch the DNA kits, is careful to say the ethnic breakdown "is an estimate but it's a very, very good estimate".

On the tricky privacy front, Ancestry insists it takes the issue very seriously though would be bound by legal orders in the countries it operates.

Ancestry is one of dozens of companies mining genetics to take advantage of the ease which consumers can access data, coupled with the apparent hunger to discover personal histories. In New Zealand, the appetite is driven by high levels of interest in commemorations such as the centenary of World War I.

Criticism has accompanied the expansion of the genetic ancestry business.

When the the US TV show Who Do You Think You Are? went on the road offering tests to discover links to English nobles or Roman soldiers, a group called Sense about Science called the results "pure speculation".

British geneticist Mark Thomas called the work "genetic astrology".

Dr Geoff Chambers, a senior research and teaching fellow in molecular biology and evolution at Victoria University advises caution.

He says the ethnic fractions - say 10 per cent Irish - do not mean that 10 per cent of your ancestors came from Ireland, but were part of a genepool that could include Celts, Scots, English and Norman French.

"The danger exists that one may go in search of romantic, but illusory ancestors," he says. On the subject of long-lost relatives, Dr Chambers says: "What is a 3rd or 4th cousin (perhaps even once removed) anyway? I am a professional geneticist and I have trouble figuring this sort of thing out."

His view? "Learning about ancestry can be fun, empowering and enlightening - but please don't let us take it all too seriously."

Argent's view is that people should expect surprises to surface from what he calls a marriage of science and history. A surprise, perhaps, like dd-moss snr.