This thesis emphasises human capital accumulation in early life, and analyses whether and how interruption of this accumulation process in childhood will influence both the stock of human capital and other socioeconomic outcomes in adulthood. Based on the theoretical framework of dynamic complementarity and the foetal origin hypothesis, Chapters 2, 3 and 4 provide empirical evidence on the life cycle mechanism of human capital investment. Chapter 2 analyses the relationship between household income and infant mortality in developing countries. Using international commodity prices as a source of exogenous variation in household income, this study discusses the potentially different influences of labour-intensive and capital-intensive commodity price changes on infant mortality, a marker of investments in child health. Using comparable Demographic and Health Survey data for 65 developing countries, this chapter finds that infant mortality is decreasing in labour-intensive commodity prices, whereas it is increasing in capital-intensive commodity prices. Chapter 3 examines the long-run consequences of exposure to natural disasters in early life using the event of the Valdivia earthquake in Chile in 1960, the largest recorded earthquake in history. It analyses whether human capital stocks were lower for cohorts exposed to this disaster at birth, or whether they had recovered three to four decades later. The results show that children born in Valdivia after the earthquake had lower schooling, a deficit of 1.5 months on average compared with earlier birth cohorts, but there are no significant differences in their health and socioeconomic status. Chapter 4 studies the influences of educational disruption on human capital accumulation and labour market performance in the long term in the context of the Chinese Cultural Revolution which imposed school and university closure. Using China census and survey data, this chapter reveals that approximately two million students were unable to finish their education, and there were unfavourable impacts on their employment status, job quality and income.