What the Experts say about Autosomal DNA percentages:
Autosomal DNA is inherited from both parents. It is randomly shuffled up in a process called recombination and the percentage of autosomal DNA is diluted with each new generation. The following figures show the average amount of autosomal DNA shared with close relatives:
- 50% mother, father and siblings
- 25% grandfathers, grandmothers, aunts, uncles, half-siblings, double first cousins
- 12.5% first cousins, half-aunts/uncles, half-nephews/nieces
- 6.25% first cousins once removed
- 3.125% second cousins, first cousins twice removed
- 0.781% third cousins
- 0.195% fourth cousins
- 0.0488% fifth cousins
- 0.0122% sixth cousins
- 0.00305% seventh cousins (ca 92,000 base pairs)
- 0.000763% eighth cousins (ca 23,000 base pairs)
The percentages can vary. For example, a brother might share 52% of his DNA with one sibling and 47% with another sibling. Because of the random way that autosomal DNA is inherited third, fourth and more distant cousins will not necessarily match you with a Family Finder or Relative Finder DNA test. According to Family Tree DNA's figures the Family Finder test has a greater than 90% chance of detecting a match with a third cousin, but just over a 50% chance of detecting a match with a fourth cousin. In contrast the test will sometimes pick up traces of autosomal DNA from your more distant cousins (for example, fifth cousins and beyond).
Source: International Society of Genetic Genealogy, www.isogg.org accessed September 8, 2013.
In looking at my autosomal DNA, I find that ALL of my ancestry for the past several generations is located in Europe, in particular, the European Coastal Islands, i.e., Great Britian/Ireland. I have had my at-DNA tested at the big three and they all return similar results.