Final answer:
The most rapid increases in average longevity at birth in the first half of the 20th century were largely due to improvements in public health, changes in public behavior, and advances in medicine.
Step-by-step explanation:
The most rapid increases in average longevity at birth occurred in the first half of the 20th century largely due to a combination of factors, including improvements in public health, changes in public behavior, and advances in medicine.
First, systems for providing clean water and disposing of human waste helped prevent the transmission of many diseases that were common in the early 20th century. This led to a decrease in infant mortality rates and an increase in life expectancy at birth.
Second, changes in public behavior, such as practicing proper hygiene and reducing risky behaviors like smoking, also contributed to longer life expectancy. People learned the importance of washing hands, protecting food from flies, and taking precautions to limit sexually transmitted diseases.
Lastly, medicine played a significant role in extending lives. Scientists developed immunizations for diseases like diphtheria, cholera, pertussis, tuberculosis, tetanus, and yellow fever between 1890 and 1930. The discovery of penicillin in 1941 and subsequent development of other antibiotic drugs helped bring infectious diseases under control.
In recent decades, drugs that reduce the risks of high blood pressure have also had a dramatic effect in extending lives.