Certain blocks of the DNA can help look back into deep history, most of it before documentary records. Typically, DNA results can be a bit of a muddle because our ancestors have happily had mixed relationships over thousands of years. DNA results gives an estimate
of origin based on where other people who have been tested come from. So we find a lot of people with a particular haplogroup result dominate the population today in a paricular place; consequently the hypothesis is that, therefore, if you have that haplogroup in your mix your ancestiors have passed through that place.
This should tell you, hopefully, that the estimate is based on a statistical prevalence of a haplogroup in an area and that the results are fluid, as more people testing may change the statistics. Be in no doubt though - we all come out of Africa.
When we look at genetic origin you may be forgiven in believing that the more complicated (expensive) the test the more accurate the result. Well yes... and no! A test that looks at 111 DNA markers says I have a lot of connections with the United States of America. For origin purposes this useful explains the problem with the interpretation of results because that does not mean Dowlings original from there; it just means a lot of folks in the USA have had tests! This is quite a common phenomena - many immigrant populations are interested in their origins and perhaps more so than native populations.
So, in other words DNA results can show where your DNA is NOW, not necessarily where it was!. The answer, until more people have the deeper tests, is to use a lower resolution test which has been taken by more people?
Now testing a lower resolution provides many more countries where the DNA is found and adds Australia, Brazil, Canada, Chile, etc. even more immigrant tests. But what does start to show is a dominence (in total) of Western European countries. The latter can be small individually but overall more of this DNA is found in Western Europe than in the USA which, as we know, generally originated from Western Europe anyway.