By studying Y chromosome DNA from a large group of men on the Mediterranean island of Sardinia, scientists not only have reconstructed the timing and course of much of the prehistoric events in Sardinia but also provided important information about early peopling in Europe and even about the time of origin of modern humans. The study is based on the fact that DNA varies in individuals because it undergoes heritable biochemical changes, known as mutations. The mutations occur rarely, but accumulate in successive generations, so that individuals (and their descendants) have a collection of the mutations that occurred in their progenitors. Determining the sequence of the DNA and comparing the mutations between different individuals or populations in different areas of the world, provides a written biochemical record of their similarities and differences, and if we know the rate at which mutations occur, the accumulating mutations provide a molecular clock of the development and branching or separation of population groups. The Y chromosome is particularly well suited for this DNA-based reconstruction of past events. This is because unlike our other chromosomes, the Y chromosome is found only in a single copy and only in males. As a result, mutations that occur on a Y chromosome stay on Y, and their accumulation is easy to track. We found mutations in Sardinian Y chromosomes that permit dating back to ancient ancestors who lived in Africa 180,000-200,000 years ago, and from there to their descendants who settled regions of Europe, including various parts of Sardinia.
The study was possible because of advances in DNA sequencing and analysis that identified mutational changes and also determined the rate of mutation. The work involved intensive collaboration among researchers from 3 Sardinian groups — the IRGB-CNR, that coordinated the study, the University of Sassari, and the Center for Advanced Studies, Research and Development in Sardinia (CRS4) – and the American groups of Goncalo Abecasis at the University of Michigan and David Schlessinger at the National Institute on Aging.
The study is dedicated to the memory of Laura Morelli, who gave a key contribution to the study and passed away some months before it was published.
Low pass DNA sequencing of 1,200 Sardinians reconstructs European Y chromosome phylogeny
Francalacci et al Science, 2013 Aug 2;341(6145):565-9.
See also Editorial. Cann RL. Y weigh in again on modern humans. Science. 2013 Aug 2;341(6145):465-7.
doi: 10.1126/science.1242899. See also editorial