Changes in the Biological State Index over the last 15,000 years of human evolution. The index value is a probability that an average person will be able to fully participate in reproduction of the next generation. The lower the index value the greater the opportunity for natural selection. Labels in the formula are: dx = a fraction of dying people of age x; sx = reproductive value of a person of age x (for example, s65 = 0, while s15 = 1). For further explanation and data see [35, 70].