Death rates in the 20th century fever, polio, measles, hepatitis among others. However, war, genocide and Holocausts have led to many millions of deaths throughout the century, and late in the century AIDS had already killed millions, particularly in Africa and south-east Asia. Cancer also killed millions via lifestyle and pollution generated by increased work in factories. During the 20th century, an enormous improvement in public health led to an overall decrease in death rates. Infant mortality rates and maternal mortality rates have dramatically decreased. In the early 1900s, 6-9 women died in pregnancy-related complications for every 1,000 births, while 100 infants died before they were
20th century in ichnology excavation of fossil footprints in history. In the Lee Stokes reported unusual footprints he interpreted as the first known pterosaur tracks. This attribution would be controversial much of the rest of the century but has since been vindicated. The dinosaur footprints of Dinosaur Ridge in Colorado were also discovered and studied in the 20th century. The advent of the dinosaur renaissance and the publication by R. McNeil Alexander of a formula which could reconstruct their running speed based on data from fossil trackways brought renewed interest and prestige to ichnology during the late 20th century. This led to several symposia