My family thought for generations that we had a Cherokee ancestor.

[WePurrsevere]

7. While it's possible that it's a family myth, it's also possible that it isn't...

8 generations ago would have a very slim chance of showing up as is explained in the part of the article that I link to and quote below. The full article has embedded links that are also helpful.

http://www.rootsandrecombinantdna.com/2015/03/native-american-dna-is-just-not-that.html

Three Reasons Why Native American DNA Does NOT Show Up On Your Test Results ...

(1) Your "full-blood" Native American ancestor may have lived so far back in time that your NA ancestor's DNA has "washed out" by the time it reached your generation.
According to 23andMe, Native American DNA has been known to "wash out" in a few short generations (about 5), especially if none of your other progenitors introduced it along the way. Wash-outs usually occur during Random Genetic Recombination, when DNA gets randomly remixed as it passes from parent to child --- some of it (ethnic components/DNA sequences from our direct fore-parents) eventually gets lost over time. This is because each child inherits random DNA contributions from his/her 2 parents (50% each); 4 grandparents (25% each); 8 g-grandparents (12.5% each); 16 gg-grandparents (6.25% each); 32 ggg-grandparents (3.125%); 64 gggg-grandparents (1.56% each), etc. as the table here illustrates:


As you can see the farther your NA ancestor is removed from your generation, the more likely your average DNA contributions from this NA is to show up in low admixture percentages or none at all. For example, if one of your 32 ggg-grandparents was full-blood Native American, you stand to inherit up to 3.125% of that ggg-grandparent's DNA. Since the DNA you will inherit from your parentage is RANDOM and your ancestors will rarely be 100% of any one ethnicity, it is theoretically possible for you to inherit non-Native American DNA from this ancestor if other ethnic components are present and according to when this NA ancestor was introduced to the bloodline. For example Native Americans are known to have varying amounts of East Asian and Eurasian admixture due sharing ancestral populations with them. And after 15th century, Native Americans became admixed with Europeans and Africans.

NOW HERE'S THE TRICKY PART! You don't inherit your reshuffled DNA in fixed percentages as the chart above suggests. Rather you inherit your DNA sequences in chunks or segments of varying "lengths" (aka CentiMorgans) as shown in this illustration:


So starting with your grandparents, you will actually NOT get 25% DNA equally from each one. Instead the contributions per grandparent could be more like:

15% from grandparent #1
35% from grandparent #2
40% from grandparent #3
10% from grandparent #4

Now imagine if we apply my "genetic formula" to your grandparent #4, who in turn was descended from your hypothetical Native American ggg-grandparent mentioned earlier. Your grandparent #4 could have only inherited about 12.5%(+/-) NA DNA from his g-grandparent (full blood Native American) and it might be less than average amount.

Question: How much of the 10% DNA you inherited from your grandparent #4 will consist of the 12.5%(+/-) Native American DNA contribution that he received from his g-grandparent (= ggg-grandparent)?

At the 5th generation for YOU, chances are equally likely to be anywhere 0.00% to 3.125%(+/-) NA DNA depending on how much NA DNA grandparent #4 gave your parent, and if your parent passed any of it to you (see How Much Of Your Genome Do You Inherit From a Particular Grandparent). While you will definitely inherit DNA from your grandparent #4 (@ 10%), it may not include any DNA that can identified as Native American. In my own family I have a relative who did not receive any NA DNA from his parents, even though his father has a NA mtDNA haplogroup (B2) and whose DNA-tested close paternal relatives (aunt, uncle, cousins) scoring 2%(+/-) NA (inclusive of shared NA DNA segments). Instead my relative got 4% Southeast Asian (SEA). He just didn't get any of the NA DNA from his father, noting the SEA component in this branch of my family is related to Malagasy peoples (see Sergio Tofanelli, et al and Teresa Vega's blog) ancestry, and much stronger than the Native American. Go figure.

(Con't at link above)