Having taken an autosomal DNA test with both Ancestry and 23andMe, I often find the visual tools offered by the testing companies to be useful and fun to examine.*
Of course the time span is quite broad, but looking at the Native American ancestry, on my own time line, it does coincide with the life span and the period of exposure that my African ancestors had to the documented Native ancestor. I do point out that most features on the three major autosomal testing sites should be considered simply tools, and DNA testing for genealogical insight is still in its infancy. So there is nothing conclusive, or detail-specific from the time line. And research most definitely continues on all of my lines, and the effort to document the family and to tell the story is one that continues.
But for those who have taken autosomal tests with 23andMe, AncestryDNA or FamilyTreeDNA there are numerous tools to explore as they may assist one with providing other insights into the past, and can give one more to add to the family narrative.
*(Note that several years ago some DNA tests were conducted in Oklahoma for those wishing to illustrated Native American DNA. However the test utilized was not an autosomal tests, so many who took those tests received "false" negative reports. Autosomal tests are more reflective of the ethnic percentages of one's ancestral background and it is suggested that individuals take one of those three autosomal tests available.)