Genome Of A Man Born In 1784 Recreated From The DNA Of His Descendants
from the I-am-your-(great-great-great-grand)-father dept
The privacy implications of collecting DNA are wide-ranging, not least because they don’t relate solely to the person from whom the sample is taken. Our genome is a direct product of our parents’ genetic material, so the DNA strings of siblings from the same mother and father are closely related. Even that of more distant relations has many elements in common, since they derive from common ancestors. Thus a DNA sample contains information not just about the donor, but about many others on the relevant family tree as well. A new paper published in Nature Genetics (behind a paywall, unfortunately) shows how that fact enables the genomes of long-dead ancestors to be reconstructed, using just the DNA of their descendants.
As an article in Futurism explains, the unique circumstances of the individual chosen for the reconstruction, the Icelander Hans Jonatan, aided the research team as they sought to piece together his genome nearly two centuries after his death in 1827. The scientists mainly came from the Icelandic company deCODE Genetics, one of the pioneers in the world of genomics, and highly-familiar with Iceland’s unique genetic resources. The following factors were key:
For one, Jonatan was the first Icelandic inhabitant with African heritage. Iceland also boasts an extensive and highly detailed collection of genealogical records. The combination of Jonatan’s unique heritage and the country’s record-keeping for inhabitants’ family trees made this remarkable recreation possible.
For cultural and historical reasons, Iceland has one of the most complete genealogical records of any nation. This allowed the research team to establish with high probability 788 of Jonatan’s descendants. Samples were taken from 182 of those individuals and then genotyped — a kind of DNA screening. The deCODE group picked out those genomes most likely to provide the longest DNA sequences that had been passed down through the generations from Jonatan’s mother, by looking for fragments of African-pattern chromosomes amidst the otherwise European genetic material. The full genomes of 20 of those 182 were sequenced, and then the parts derived from Jonatan’s African ancestry pieced together to recreate 38% of his mother’s DNA. From this, the researchers were able to establish that Jonatan’s mother was probably from the African region spanned by Benin, Nigeria and Cameroon.
This kind of large-scale reconstruction in the absence of physical samples has never been achieved before, and is certainly a major triumph of biological and computational technology. An important question is whether this is a one-off, made possible by the unique circumstances of Jonatan’s life, or whether it could be applied more widely. According to the Futurism article:
Theoretically, a technique like this could help researchers create “virtual ancient DNA,” which would allow scientists to recreate the DNA of historical figures. Agnar Helgason of deCODE stated that “Any historic figure born after 1500 who has known descendants could be reconstructed.”
While it’s exciting, there are still major hurdles to overcome in terms of the potential future applications. The quantity, scale, and detail of the DNA from living ancestors required to recreate a person’s DNA make it impractical for use within most families. Additionally, with each new generation identifiable DNA fragments get smaller and more difficult to work with.
As DNA sequencing becomes cheaper and more accurate, it will be possible to carry out DNA profiling and collection faster and more economically. Similarly, as computational power increases, chromosome fragments can be analyzed and stitched together more easily. In due course, these kinds of genomic reconstructions will probably become more common. Already, deCODE’s research confirms how DNA can establish the connections not just between present-day members of a family, but also with those long dead. When unexpected patterns of maternity or paternity are revealed, they will bring with them who knows what social consequences for their descendants.