process of development since the emergence of Homo sapiens. Galor, who founded the field of unified growth theory, identifies the historical and prehistorical forces behind the differential transition timing from stagnation to growth and the emergence of income disparity around the world. He unveils the mechanisms that have trapped the world economy in millennia of near-stagnation but ultimately has induced the remarkable transition to an era of sustained economic growth characterized by vast inequality across countries and regions. Unified Growth Theory suggests that during most of human existence, technological progress was counterbalanced by population growth and living standards were near subsistence across time and space. However, the reinforcing interaction between the rate of technological progress and the size and composition of the population has gradually increased the pace of technological progress, enhancing the importance of education in the ability of individuals to adapt to the changing technological environment. The rise in the allocation of resources towards education triggered reductions in fertility rates, enabling economies to divert a larger share of the fruits of technological progress to the growth of income per capita, rather than towards the growth of population, paving the way for the emergence of sustained economic growth. The theory further suggests that variations in biogeographical characteristics, as well as cultural and institutional characteristics, have generated a differential pace of transition from stagnation to growth across countries and consequently divergence in their income per capita over the past two centuries. Reception Robert Solow described Galor's project as "breathtakingly ambitious". He added that "Galor proposes a fairly simple, intensely human-capital-oriented model that will accommodate the millennia of Malthusian near-stagnation, the Industrial Revolution and its aftermath of rapid growth, the accompanying demographic transition, and the emergence of modern human-capital-based growth. And the model is supposed to generate endogenously the transitions from one era to the next. The resulting book is a powerful mixture of fact, theory, and interpretation." According to Daron Acemoglu, "Unified Growth Theory is a work of unusual ambition" that "will inspire, motivate, and challenge economists." Steven N. Durlauf declared that "Unified Growth Theory is Big Science at its best. It grapples with some of the broadest questions in social science, integrating state-of-the-art economic theory with a rich exploration of a wide range of empirical evidence." He considers that Galor's ideas "will have a lasting effect on economics." The Journey of Humanity: The Origins of Growth and Equality (Penguin