growth. Throughout human history, energy production was the main constraint on economic development, and new technologies allowed humans to significantly increase the amount of available energy. First came fire, which made edible a wider variety of foods, and made it less physically demanding to digest them. Fire also enabled smelting, and the use of tin, copper, and iron tools, used for hunting or tradesmanship. Then came the agricultural revolution: humans no longer needed to hunt or gather to survive, and began to settle in towns and cities, forming more complex societies, with militaries and more organized forms of religion. Technologies have contributed to human welfare through increased prosperity, improved comfort and quality of life, and medical progress, but they can also disrupt existing social hierarchies, cause pollution, and harm individuals or groups. Recent years have brought about a rise in social media's cultural prominence, with potential repercussions on democracy, and economic and social life. Early on, the internet was seen as a "liberation technology" that would democratize knowledge, improve access to education, and promote democracy. Modern research has turned to investigate the internet's downsides, including disinformation, polarization, hate speech, and propaganda. Since the 1970s, technology's impact on the environment has been criticized, leading to a surge in investment in solar, wind, and other forms of clean energy. Social Jobs Since the invention of the wheel, technologies have helped increase humans' economic output. Past automation has both substituted and complemented labor; machines replaced humans at some lower-paying jobs (for example in agriculture), but this was compensated by the creation of new, higher-paying jobs. Studies have found that computers did not create significant net technological unemployment. Due to artificial intelligence being far more capable than computers, and still being in its infancy, it is not known whether it will follow the same trend; the question has been debated at length among economists and policymakers. A 2017 survey found no clear consensus among economists on whether AI would increase long-term unemployment. According to the World Economic Forum's "The Future of Jobs Report 2020", AI is predicted to replace 85 million jobs worldwide, and create 97 million new jobs by 2025. From 1990 to 2007, a study in the U.S by MIT economist Daron Acemoglu showed that an addition of one robot for every 1,000 workers decreased the employment-to-population ratio by 0.2%, or about 3.3 workers, and lowered wages by 0.42%. Concerns about technology