The Science section of the New York Times published a wonderful article this weekend titled Tales of African-American History Found in DNA. The article details the findings of a study published in PLOS Genetics conducted by geneticist Dr. Simon Gravel who analyzed the DNA of 3,726 African Americans to assess genetic diversity.
Here’s what the study found:
Admixture profile: African-Americans today are on average 82.1 percent African, 16.7 percent European and 1.2 percent Native American.
When admixture was introduced: Native American admixture within African Americans presents in tiny segments which likely means the DNA was introduced in the early 1600s after the first enslaved persons arrived in the American Colonies. European admixture presents in longer segments which offers proof that white men and enslaved women regularly produced offspring prior to the Civil War.
Detecting migration patterns in DNA: The Great Migration, which was the movement of millions of African-Americans out of the rural South and into Northern, Midwestern and Western cities between 1910 and 1970, can be traced through DNA connections among African Americans.
I also took away that the genetic diversity represented within African Americans re-enforces how much the concept of race is a social construct with no basis in genetics. However being able to know genetic profiles of African-Americans can be very important for purposes of medical discoveries. The only way to truly tease any value from genetic profile results for medical discoveries is to fully deconstruct the results down to the original African, European and Native American DNA chunks we inherit, and then analyze those chunks for potential genetic meaning.
Each of us inherits 23 pairs of chromosomes from our parents. Here is a visual representation of my genome (called a chromosome painting) which came with the results I received after testing with the DNA service 23andMe. The chromosome painting is color coded based on the origins of the ethnic chunks I inherited from my parents. All of the magenta colored chunks represent my African ancestry; the blue chunks represent my European Ancestry; and the yellow/orange chunks represent my Native American and East Asian Ancestry.
Here’s how my results compare with the study:
Admixture profile: According to 23andMe I am 60.4% African, 37.6% European, 2.0% Native American, East Asian and unknown. My individual results represent a more diverse profile as compared to African Americans on average as identified in the study. This diversity may be attributable to my multi-ethnic Cumbo ancestry as well as descending from ancestors who were the products of successive generations of offspring between white men and enslaved women prior to the Civil War.
When admixture was introduced: My genome includes long, uninterrupted African (magenta) DNA chunks offering proof of my deep West African ancestral roots, mingled with long European (blue) DNA chunks which offers proof that I descend from the offspring of white men and enslaved women born decades prior to the Civil War. It also includes one long orange/yellow chunk (on chromosome 1) which seems to indicate that I descend from at least one predominantly Native American ancestor, likely within the last few hundred years.
My genome also includes stretches of painting that alternate between magenta, blue and sometimes orange/yellow in very short chunks. This is likely indicative of the DNA I inherited from my Cumbo ancestors and other free people of color ancestors who’d been multi-ethnic for many generations dating back to the first Africans and Europeans to arrive in 1600s Colonial Virginia.
Detecting migration patterns in DNA: I can actually trace two distinct Cumbo migration patterns within my DNA. The first is the Great Migration. My 4th great grandfather was Britton Cumbo Jr. born around 1825 and died in Northampton NC around 1899. He had at least 7 children. Their descendants typically show up as 4th or 5th cousin matches to me within my DNA results. Through research and outreach I’ve discovered that many Britton Cumbo family branches migrated to Baltimore, Philadelphia, New York City and New Jersey in the early 1900s in search for work in the city an to escape the segregated south and rural farming life.
The second migration pattern I’m able to detect is more distant. My results include DNA matches who are Lumbee Indian or Lumbee Indian descended. They trace their Cumbo ancestry back to a man named Cannon Cumbo who settled into Robeson County, North Carolina in the late 1700s. My more distant connection to them offers clues that our shared Cumbo ancestors likely lived in Virginia in the 1600s and early 1700s and that our respective Cumbo family lines then branched off and by the late 1700s had migrated to different parts of North Carolina – mine to Northampton County and theirs to Robeson County.
What have you uncovered about your Cumbo ancestry through analyzing your DNA results? Please feel free to share your stories in the comments section of this blog.