> A lot of people think it has to do with environmental factors, and specifically lead. Ironically, we are studying whether lead caused cohesion problems for t

> A lot of people think it has to do with environmental factors, and specifically lead. Ironically, we are studying whether lead caused cohesion problems for the Roman Empire [1] [2], so it isn't as if we didn't suspect lead before to cause civilization-scale problems. And while the modern drop in blood lead levels is big in the developed world [3], it is still orders of magnitude greater than pre-industrial levels. [1] https://www.forbes.com/sites/kristinakillgrove/2019/11/29/archaeological-skeletons-from-london-prove-some-romans-were-lead-poisoned/?sh=7d09a64c48cc https://www.forbes.com/sites/kristinakillgrove/2019/11/29/ar... [2] https://penelope.uchicago.edu/~grout/encyclopaedia_romana/wine/leadpoisoning.html https://penelope.uchicago.edu/~grout/encyclopaedia_romana/wi... [3] https://www.who.int/docstore/bulletin/pdf/2000/issue9/bu0686.pdf https://www.who.int/docstore/bulletin/pdf/2000/issue9/bu0686...