AFTER four years a Scottish DNA ancestry research company has completed the first stage of an epic piece of research tracing the beginnings of a family tree for “all men on Earth”.
Award-winning broadcaster and historian Alistair Moffat who runs ScotlandsDNA has produced The Great Tree of Mankind revealing for the first time details of one of the most important moments in human history when the tree suddenly and dramatically changed shape.
About 4,500 years ago, many new branches appearAlistair Moffat
All men trace their Y chromosome ancestry back to an individual scientists call “Adam” thought to have lived in Africa about 210,000 years ago.
Males pass on the Y chromosome to their sons, the single largest piece of DNA inherited as a block, which can be used to research ancestry back into the mists of prehistory. When new genetic variants, called markers, occur with successive generations, scientists and historians can trace them and their movements from Africa to their present locations.
Men with the same markers form haplogroups which can be found in high concentrations in specific parts of the world.
The branches of the tree immediately below Adam were seen to divide only very slowly over a long period of time.
This is because he and his descendants were hunter-gatherers who probably lived in family bands living off a wild harvest of roots, fruits, fungi and animals they could trap, with the population growing slowly.
Mr Moffat said: “But then the Great Tree abruptly changes. About 4,500 years ago, many new branches suddenly appear over a very short period.
“This is noticeable across the whole Tree but particularly clear under the very British and European Y chromosome haplogroup, R1b S145, where a staggering 25 new branches are found.
“What this means is something simple yet hugely significant – many more children being born and surviving to adulthood.
The men born at this time created new sub-types in the Y chromosome Tree which then created more in a huge lateral expansion.
There was no corresponding expansion of mitochonrial DNA which only women pass on to all their children.”
Mr Moffat said DNA research showed this was highly likely to indicate an invasion by a warrior elite, small bands of highly aggressive and sexually predatory men sailing by small boats to Britain and Ireland over a short space of time around 2,500BC from Spain, Portugal and southern France.
ScotlandsDNA, with assistance from Dr James F Wilson of the centre for population health sciences in Edinburgh, has shown how 573 Y chromosome sub-types descend from Adam and relate to each other.