f you're Black with Type O blood, DNA traces your bloodline to the oldest human lineage on Earth — and it points to Africa. For a century, blood type was dismissed as a medical label, and people still repeat the myth that Type O is "the oldest" blood type. The truth is stranger and deeper. Modern genetics suggests Type A is the ancestral form, and Type O arose from a mutation — a mutation that first appeared in Africa, before humans ever left the continent.