Life expectancy at birth among early humans was likely to be about 20 to 30 years. It rose to between 40 and 45 by the middle of the 19th century. Rapid improvements began at the end of the 19th century, so that by the middle of the 20th century it was approximately 60 to 65 years. At the beginning of the 21st century, life expectancy at birth reached about 70 years. Two trends dominated the mortality decline: The first half of the 20th century saw significant improvements in the mortality of infants and children (and their mothers). Since the middle of the 20th century, gains in life expectancy have been mainly due to medical factors that have reduced mortality among older persons (reductions in deaths due to the “big three” killers – cardiovascular disease, cancer and strokes).