Do Individuals with a Common Ancestor 10 to 12 Generations Ago Share DNA?
Understanding the genetic relationships between individuals who share a common ancestor several generations back is an intriguing aspect of genealogy and genetics. Specifically, would individuals with a common ancestor 10 to 12 generations ago have any DNA in common? This article delves into the intricacies of genetic inheritance and how shared DNA decreases with each generation.
Generational Timeframe and DNA Inheritance
A generation is typically considered to be around 25 to 30 years. Therefore, 10 to 12 generations would span approximately 250 to 360 years. Each individual inherits half of their DNA from each parent, and this process continues with each generation. As you go back in generations, the amount of shared DNA decreases due to the way genetic material is recombined through meiosis.
Shared DNA and Relationship Percentages
On average, cousins share about 12.5% of their DNA. However, this percentage decreases with more distant relationships. For instance:
Second cousins share about 3.125% of their DNA. Third cousins share about 0.78% of their DNA.By the time you reach a common ancestor 10 to 12 generations back, the shared DNA might be very small, possibly less than 1%.
Genetic Testing and Shared DNA
Genetic testing services can help identify shared DNA segments and estimate the degree of relatedness. These tests can reveal connections that may not be immediately apparent through traditional genealogical research. By comparing DNA test results, one can trace back generations and uncover family connections.
Modern DNA Genetics in Historical Context
It's important to remember that even individuals who share a common ancestor 10 to 12 generations back will have some shared DNA, though the amount is likely to be relatively small. Modern Europeans carry DNA going back 8000 to 4000 years to Neolithic farmers from Anatolia and Indo-Europeans. A small percentage of Britons and other Europeans still carry the Haplogroup of Cheddar Man, whose remains were found in England and dated to about 9100 years ago.
Correction Note
Please note that the answer previously provided had significant inaccuracies and has been rewritten to correct the mathematical and genetic assumptions. The revised explanation considers the probability of inheriting DNA from a particular ancestor and how this probability decreases with each generation. Importantly, unlikely events, such as an ancestor not passing on any DNA, are accounted for in the calculations.
While individuals with a common ancestor 10 to 12 generations ago will have some shared DNA, the amount is likely to be relatively small and can vary widely among individuals. Genetic tests and probabilistic calculations offer insights into these complex relationships, shedding light on the genetic heritage of families across time.
Further, pedigree collapse (where an ancestor appears in several places in the family tree) is not always relevant to these calculations, as we focus on the unique numbers of ancestors to account for the inheritance pattern.