Chaim She­ba, a sur­geon gen­er­al of the Israeli army and lat­er the direc­tor gen­er­al of the Israeli Min­istry of Health, was also a col­or­ful, pio­neer­ing Israeli geneti­cist. Ear­ly in his career, She­ba stum­bled into human genet­ics in the process of prepar­ing to prac­tice med­i­cine in his adopt­ed coun­try. Born in Aus­tria, he left for Pales­tine with a ​“still wet” med­ical school diplo­ma from the Uni­ver­si­ty of Vien­na expect­ing to ​“dry the unin­hab­it­ed swamps.” Dry­ing the swamps was a way to elim­i­nate malar­ia, a dis­ease com­mon not only in Pales­tine, but through­out the coastal Mediter­ranean basin. While on the boat to Pales­tine, She­ba read a book about trop­i­cal dis­eases and learned that one of the major com­pli­ca­tions of malar­ia was black­wa­ter fever. Typ­i­cal­ly, the ​“black water” urine of indi­vid­u­als with red blood cells dis­rupt­ed by malar­i­al par­a­sites con­tained the dark-col­ored break­down prod­ucts of the oxy­gen-car­ry­ing pro­tein, hemo­glo­bin.

When She­ba arrived in Pales­tine, he learned about an unex­pect­ed spring­time occur­rence of black­wa­ter fever caused by eat­ing fava beans, a pop­u­lar Mediter­ranean del­i­ca­cy. Fav­ism had been known in ancient Greek times with Pythago­ras, Dio­genes and Plutarch all warn­ing about the dan­gers of eat­ing fava beans. Eat­ing the beans or even smelling the pollen caused a sud­den ill­ness of abdom­i­nal pains and vom­it­ing, fol­lowed by pal­lor, jaun­dice and brown-col­ored urine – all result­ing from the rapid break­down of red blood cells. Dur­ing the 1930s, all of the patients that She­ba observed with fav­ism were Jew­ish males of Iraqi, Yemenite or Kur­dish ori­gin. Dur­ing World War II, while serv­ing as a sur­geon in the British Army, She­ba observed men who expe­ri­enced severe break­down of red blood cells result­ing from inges­tion of the new­ly devel­oped antibi­ot­ic and anti-malar­i­al drugs. These reac­tions occurred pri­mar­i­ly among Iraqi, Turk­ish, Greek, Yemenite and Kur­dish Jew­ish sol­diers, and were also com­mon among non-Jew­ish Greek and Cypri­ot sol­diers, and Ital­ian pris­on­ers of war. To She­ba, it was strik­ing that Ashke­nazi Jews did not share these sen­si­tiv­i­ties that were preva­lent among their co-religionists.

The rea­son for this dif­fer­ence between the Ashke­nazi and oth­er Jews became appar­ent after the war — an inabil­i­ty to repair dam­age to red blood cells that result­ed from expo­sure to agents that were non-tox­ic to the major­i­ty of the pop­u­la­tion. This inabil­i­ty occurred in indi­vid­u­als who are defi­cient for the enzyme, glu­cose-6-phos­phate dehy­dro­ge­nase (G6PD). As its name would sug­gest, G6PD nor­mal­ly breaks down the sug­ar, glu­cose, and, in the process, gen­er­ates an antiox­i­dant that repairs red blood cells. Although G6PD is pro­duced and used by all of the cells of the body, only red blood cells are sen­si­tive to the effects of oxi­diz­ing agents. The enzyme is encod­ed by a gene on the X chro­mo­some and men who car­ry a mutant gene on their sin­gle X chro­mo­some are sus­cep­ti­ble to these expo­sures. Women who have two copies of the X chro­mo­some are rel­a­tive­ly resis­tant to this con­di­tion when one of their X chro­mo­somes car­ries a mutant G6PD gene.

Over time, She­ba rec­og­nized that oth­er genet­ic dis­eases (Tay-Sachs, Gauch­er, famil­ial Mediter­ranean fever) were found almost exclu­sive­ly with­in cer­tain Jew­ish groups, reflect­ing the unique his­to­ry of those groups. He assumed that these dis­eases were caused by trans­mis­sion of a mutant gene that occurred some­time in the dis­tant past, and then trans­mit­ted by a group of ​“founders” who migrat­ed to that site of the Jew­ish Dias­po­ra. This phe­nom­e­non has come to be known as a ​“founder effect.” She­ba was fond of using Bib­li­cal genealo­gies and spoke of con­di­tions being trans­mit­ted by the descen­dents of the sons of Noah or oth­er, lat­er Bib­li­cal char­ac­ters. Thus, She­ba estab­lished the notion that these dis­eases serve as genet­ic mark­ers for the pop­u­la­tions in which they occurred. Although not all of the mem­bers of the pop­u­la­tion car­ried these mutant genes, enough do to rec­og­nize a shared genet­ic legacy.