Neanderthals’ blood type may help explain their demise, new study finds

Blood Tale of Extinction: How Humans’ Evolution Outpaced Neanderthals

In the grand journey of modern humans out of Africa, a fascinating story unfolds in the humble yet vital red blood cells. These tiny warriors may have played an unsuspected role in the eventual demise of our closest ancient relatives, the Neanderthals.

A groundbreaking study, published in Scientific Reports, reveals that humans’ blood groups have evolved rapidly, while those of Neanderthals remained largely unchanged. This discrepancy may have been their undoing.

Humans have eight possible combinations of blood groups and Rh factors, with countless lesser-known antigens. But Neanderthals had a rare blood group that could spell trouble for their newborns. Mating between Neanderthal females and either humans or Denisovans could lead to a life-threatening condition called hemolytic disease of the newborn, characterized by jaundice, anemia, and even brain damage.

The reason behind most humans having the Rh protein on their red blood cells is still a mystery. However, when an Rh-negative person is pregnant with an Rh-positive fetus, the mother’s immune system may create antibodies that attack the fetus’s red blood cells, also leading to hemolytic disease of the newborn. Today, this is treatable with a lab-made antibody called immunoglobulin. But 100,000 years ago, such treatment would have been impossible.

Evolution has favored our early human ancestors who developed diverse red blood cell variants, likely during their migration along the Persian Plateau. In contrast, Neanderthals’ red blood cells remained relatively unchanged for at least 80,000 years. This could be due to their general isolation and declining population numbers, ultimately leading to their extinction.

The intriguing tale of our different blood legacies offers insight into the dynamic forces of evolution at play during our ancient ancestors’ journey across the globe.