The majority of Ashkenazi Jews, a population that originally hails from central and Eastern Europe and represent about 80 percent of today’s Jews, all come from a population of about 350 people between 600 and 800 years ago, according to a new study reported by LiveScience. Researchers analyzed the genealogy of 128 Ashkenazi Jews and compared them to the genes of a reference group of 26 Flemish people and were able to pin-point what genes were uniquely Ashkenazi. The number of similarities within the uniquely Ashkenazi genomes allowed researches to estimate a timeline of the originating population.

The genetic link is so close that one of the study’s researchers, Itsik Pe’er, estimates that most European Jews are at least 30th cousins, or closer. “They have a stretch of the genome that is identical,” he says. This means that notable Ashkenazi Jews, like Albert Einstein, Gene Simmons or Natalie Portman, are 30th cousins at most.

The discovery also has larger implications in terms of pre-emptively determining genetic diseases that occur within Ashkenazi populations. Tay-Sachs, a progressive genetic disease that causes nerve cells to deteriorate, and cystic fibrosis, is found more frequently among Ashkenazi Jews. This new study could help provide more streamlined analysis for individuals looking for genetic mutations or disease by eliminating sequences that are normal variations versus sequences that are unique and potentially problematic.