The Black Cochin Jewish population has a high percentage of Rh-negative blood but the Rh-negative blood type is uncommon in the Black population in general, which is exactly the same interesting phenomenon as with the Oriental Jews of Israel who have a high percentage of Rh-negative blood, where among the Chinese and Japanese, Rh-negative blood type it is almost non-existent.
Suellen Ocean is the author of Secret Genealogy – A How-to for Tracing Ancient Jewish Ancestry, Secret Genealogy II – Uncovering the Jewish Roots of Our Christian Ancestors and Secret Genealogy III – From Jewish Anglo-Saxon Tribes to New France Acadians. Available here:
Secret Genealogy II: http://www.amazon.com/Secret-Genealogy-II-Christian-Ancestors/dp/1484053222
Secret Genealogy III: http://www.amazon.com/Secret-Genealogy-III-Jewish-Anglo-Saxon-Acadians/dp/148407579X