It is a wise father that knows his own child, but today a man can boost his paternal (fatherly) wisdom -- or at least confirm that he's the kid's dad.

All he needs to do is shell our $30 for paternity testing kit (PTK) at his local drugstore -- and another $120 to get the results.

DNA testing is also the latest rage among passionate genealogists and supports businesses that offer to search for a family's geographic roots.

More than 60, 000 people have purchased the PTKs since they first become available without prescriptions last years, according to Doug Fog, chief operating officer of Identigene, which makes the over-the-counter kits.

Most tests require collecting cells by webbing saliva in the mouth and sending it to the company for testing.

More than two dozen companies sell DNA tests Directly to the public, ranging in price from a few hundred dollars to more than $2500.

Among the most popular: paternity and kinship testing, which adopted children can use to find their biological relatives and families can use to track down kids put up for adoption.

"There is a kind of false precision being hawked by people claiming they are doing ancestry testing," says Trey Duster, a New York University sociologist.

He notes that each individual has many ancestors-numbering in the hundreds just a few centuries back.

Yet most ancestry testing only considers a single lineage, either the Y chromosome inherited through men in a father's line or mitochondrial DNA, which a passed down only from mothers.

But some observers are skeptical.

All tests require a potential candidate with whom to compare DNA.

This DNA can reveal genetic information about only one or two ancestors,

even though, for example, just three generations back people also have six other great-grandparents or, four generations back, 14 other great-great-grandparents.

Critics also argue that commercial genetic testing is only as good as the reference collections to which a sample is compared.

Databases used by some companies don't rely on data collected systematically but rather lump together information from different research projects.

In addition, the computer programs a company uses to estimate relationships may be patented and not subject to peer review or outside evaluation.

This means that a DNA database may have a lot of data from some regions and not others, so a person's test result may differ depending on the company that processes the results.