Why do humans have long childhoods and slow physical growth rates compared to nonhuman primates? The embodied capital theory (ECT) posits that the hard-to-extract, energy-packed resources sought by humans require more complex cognitive and physical skills, which are acquired during a longer development period. The authors of this article test this theory through a comparative analysis of different forms of resource types and skill level by age in 28 different societies. Their findings support ECT, suggesting that long childhoods evolved as a period to develop the skills required for extracting complex resources in foraging societies.