The handkerchief is now missing from the gourd, but Lalueza-Fox and his team identified a brownish substance on the interior of the dried squash. Biochemical tests determined that the substance was dried blood.
Lalueza-Fox recalled that the king was known for his blue eyes, featured prominently in paintings. He then got the idea of looking for the blue eyes mutation within the dried blood’s DNA. The scientists found this mutation, at a gene called HERC2.
The researchers also analyzed other aspects of the blood’s genetics, such as its mitochondrial DNA profile, its Y chromosome profile and some other markers. These all revealed that the DNA profile “found inside the gourd is extremely rare in modern Eurasians,” suggesting that it may derive from a royal bloodline.