30-mn-year-old fossil holds oldest mammal blood ever found
US-based researchers have discovered the oldest known fossilised mammal red blood cells preserved in amber. Researchers believe that a blood-sucking tick was feeding on a monkey and fell into a tree sap, preserving it for 20-30 million years. The discovery also describes the only known fossils of the tick, a parasite existing till today which infects animals' blood cells.