Final answer:
Thomas Malthus argued that without war, famine, and disease to check population growth, most people were destined to be poor and miserable. Although subsequent developments in agricultural productivity and economic conditions have largely disproven his theory, it was influential in the early 19th century.
Step-by-step explanation:
The individual who argued that without wars and epidemics, most were destined to be poor and miserable was Thomas Malthus. He believed that population growth would inevitably outpace the food supply, leading to widespread poverty. To prevent this, he suggested that families should have fewer children. Malthusian theory positioned war, famine, and disease as 'positive checks' on population growth, preventing it from exceeding the earth's carrying capacity. Despite the growth in the population, the food supply also increased, thereby disproving Malthus's primary theory as the Industrial Revolution progressed. While economic conditions improved over time, and birth rates eventually declined, Malthus's early 19th-century views held significant influence during his lifetime.