Being infected by hookworms, roundworms, bacteria like H. Pylori and other pathogens, getting wounded from accidents or animal attacks, ticks, leeches and so on would all be great ways to lose blood and iron for paleolithic humans.

被钩虫，蛔虫，像幽门螺旋杆菌这样的细菌和其他病原体感染，被意外伤害或动物攻击，蜱虫，水蛭等等都是旧石器时代的人类失去血液和铁的好方法。