Ancestry.com changed how it determines ethnicity and people are upset - Note for a Discussion, "E Pluribus Unum? What Keeps the United States United."

USA TODAY NETWORK, Marc Daalder, Detroit Free Press; original article contains a video

(Photo: Ancestry)

Ancestry.com, the website better known for helping users create family trees, find distant family members and capture suspected serial killers, made a lot of customers angry last week.

Ancestry, which also is in the business of DNA testing, allows users to send a vial of saliva to the company and receive in return a detailed genetic portfolio, including risk for some diseases and estimates of their ethnic ancestry.

Neither the medical nor the heritage information are guaranteed to be 100 percent accurate, but as the science improves, so does the quality of the results. At least, that's what Ancestry insists.

After Ancestry rolled out a new update to its ethnicity estimate system last week, users noticed dramatic changes in their ethnic profiles – some of which is inaccurate, customers say.

Hey, @Ancestry Are you sure your Italian samples for the new update are accurate? I went from being 20% Italian to 5%. My bio-mom was 50% Italian and I have traced the family tree many generations on her maternal and paternal lines. What gives?!?!

— Britt (@brooklin1978) September 12, 2018

The science is simple: Ancestry compares sections of your DNA with a "reference panel" of DNA samples that it knows correspond to a certain place (say, Italy or southern Africa) to try to identify a match. The new update expands the reference panel by a factor of five, so it should be more accurate.

My first results were 49% Italian/Greece then renamed Europe South with 49% and now only 7% Italian and 0% Greece with the update. Can’t trust @AncestryDNAresults!

— Arturo S Perez (@asperez_r) September 14, 2018

Still, many users remain angry with Ancestry as their original results have, in some cases, drastically changed.

Ancestry DNA released an update 😩 im not hispanic anymore 😩😩😩

— dom (@year2000bug) September 16, 2018

My @Ancestry results have changed dramatically. I know they update based on new data but I didn’t expect the change to be so big! So long, Scandinavian ancestors. It was nice to believe you were real for a while.

— Lynne Taylor (@lynnevtaylor) September 16, 2018

Way to go @Ancestry - so this lovely estimated DNA "update" makes me suddenly less of what I *know* I am, and more of something at a higher percentile that just isn't borne out in our own verifiable genealogical research. You giveth and you taketh away! 🤬

— Michael Butler Smith (@MikeButlerSmith) September 17, 2018

Other users said they were happy with the results or found that the new results better matched what they knew of their family history.

The new @Ancestry#AncestryDNA ethnicity estimates are more accurate, and match my family tree better, after their recent update. pic.twitter.com/Bx2Ru1Fwdo

— Matt (@mfw523) September 15, 2018

My AncestryDNA update finally came through... WAAAAAY more accurate now: England has been tied to the continent, as opposed to the Celtic western-ish Isles, and my Germans are on the map at last. Several minor regions that never made sense are gone too. #genealogy#ancestry#DNApic.twitter.com/kh7Xclh4X3

— RF Tree Genealogy (@RedFeatherGenes) September 12, 2018

With the latest @Ancestry DNA update, my Scottish ethnicity has jumped 15%, meaning I’m that much closer to finding Groundskeeper Willie in my family tree. #ancestry#DNApic.twitter.com/GhzgmtFqz7

— Michael Lyons (@lyonsmw) September 16, 2018

In April it was revealed DNA from a decades-old crime scene was plugged into a genealogy website. Investigators followed family trees to try to narrow down a suspect. That search led to Joseph James DeAngelo. 

DeAngelo is suspected of being the Golden State Killer serial killer. DeAngelo, who lived in the Sacramento suburb of Citrus Heights when he was arrested in April, is accused in 12 killings, more than 50 rapes and the ransacking of more than 100 homes across California in the 1970s and 1980s. 

A spokesperson for Ancestry.com, which also has a search for the general public, said the company was not in contact with authorities in the DeAngelo case and will not share member information with law enforcement "unless compelled to by valid legal process."

At the time, Ancestry.com said it was unaware of the investigation.

Contributing: Christal Hayes and Ashley May, USA TODAY. Follow Marc Daalder on Twitter: @marcdaalder