I'm was reading this book, The Secret of Our Succes, and found this surprising quote:
“The emergence of adolescence and young adulthood has likely been crucial over our evolutionary history, since in hunting and gathering populations, hunters do not produce enough calories to even feed themselves (let alone others) until around age 18 and won’t reach their peak productivity until their late thirties. Interestingly, while hunters reach their peak strength and speed in their twenties, individual hunting success does not peak until around age 40, because success depends more on know-how and refined skills than on physical prowess. By contrast, chimpanzees—who also hunt and gather—can obtain enough calories to sustain themselves immediately”

The author lists some sources: "See Campbell 2011, Thompson and Nelson 2011, Kaplan et al. 2000, Bogin 2009, and Nielsen 2012."

I was not able to find one of these papers searching google.
1. can anyone find a paper that confirms this claim, and
2. can anyone recommend a way to easily find the corresponding paper when an author only quotes the paper's author's last name and year?

Edit: These are the papers:

• “Campbell, B. C. 2011. “Adrenarche and middle childhood.” Human Nature 22 (3):327–349.”
• “Thompson, J., and A. Nelson. 2011. “Middle childhood and modern human origins.” Human Nature 22 (3):249–280. doi:10.1007/s12110–011–9119–3.”
• “Kaplan, H., K. Hill, J. Lancaster, and A. M. Hurtado. 2000. “A theory of human life history evolution: Diet, intelligence, and longevity.” Evolutionary Anthropology 9 (4):156–185.”
• “Bogin, B. 2009. “Childhood, adolescence, and longevity: A multilevel model of the evolution of reserve capacity in human life history.” American Journal of Human Biology 21 (4):567–577.”
• “Nielsen, M. 2012. “Imitation, pretend play, and childhood: Essential elements in the evolution of human culture?” Journal of Comparative Psychology 126 (2):170–181.”