TL;DR in The Roman Empire : Peace caused Feminism, Feminism and its values caused very low fertility rates + virility drop among men ( they became more and more weak fat apathetic, homosexuality and prostitution became normal ), it resulted in a massive immigration to sustain demography and to do the dirty jobs romans didn't want to do anymore. A new religion came in and grew in followers very quickly. Government public debt skyrocketted. Politics went nuts, leaders were either hated or puppets. Most of the army was made of mercenaries ( paid immigrants because romans didn't want the dirty job anymore ). Romans were about to become a minority in Rome. Mercenaries eventually overran and pillaged the Empire.
My personal theory is this : if a country's fertility rate per woman goes below 2 for a considerable amount of time, it will end in an economical and political crisis. If that country uses immigration to sustain demography, it will end in a civil war.
Edit : I said feminism causes economical crisis... but why ? Someone linked a very nice video explaining a very plausible theory https://www.youtube.com/watch?v=w__PJ8ymliw
Please note that I didn't write any of the following text, it is a comment u / tomek77 / made 7 years ago on r / Equality / making observations about how we're following the same path as the roman empire . It ultimately led me to believe that the western part of the world will pretty much cease to exist in the next 50 years.
Unfortunately, feminism and future is an oxymoron (or fortunately, depending on your point-of-view), as it seems to be unsustainable on the long run.
Based on past history, it appears that a civilization that embraces feminist values will cease to exist in just a few centuries. This is why we have never seen a feminist civilization aside from very short spans at the end of the Roman empire and possibly a few other more ancient civilizations.
Reading the history of the roman Empire brings such glaring similarities with our own civilization, it is as if human social dynamics are literally stuck in a cycle that repeats every couple thousand years (there were two matriarchical, extremely advanced civilizations: one at the end of the Roman empire, 2000 years ago, one possibly at the end of Babylon, 4000 years ago).
For those who enjoy history, here is a short recap of social changes in Rome, 2 millenia ago (most historians focus on military and political facts, but I find the social aspects just as fascinating):
~5 century BC: Roman civilization is a a strong patriarchy, fathers are liable for the actions of their wife and children, and have absolute authority over the family (including the power of life and death)
~1 century BC: Roman civilization blossoms into the most powerful and advanced civilization in the world. Material wealth is astounding, citizens (i.e.: non slaves) do not need to work. They have running water, baths and import spices from thousands of miles away. The Romans enjoy the arts and philosophy; they know and appreciate democracy, commerce, science, human rights, animal rights, children rights and women become emancipated. No-fault divorce is enacted, and quickly becomes popular by the end of the century.
~1-2 century AD: The family unit is destroyed. Men refuse to marry and the government tries to revive marriage with a "bachelor tax", to no avail. Children are growing up without fathers, Roman women show little interest in raising their own children and frequently use nannies. The wealth and power of women grows very fast, while men become increasingly demotivated and engage in prostitution and vice. Prostitution and homosexuality become widespread.
~3-4 century AD: A moral and demographic collapse takes place, Roman population declines due to below-replacement birth-rate. Vice and massive corruption are rampant, while the new-born Catholic Religion is gaining power (it becomes the religion of the Empire in 380 AD). There is extreme economic, political and military instability: there are 25 successive emperors in half a century (many end up assassinated), the Empire is ungovernable and on the brink of civil war.
~5 century AD: The Empire is ruled by an elite of military men that use the Emperor as a puppet; due to massive debts and financial problems, the Empire cannot afford to hire foreign mercenaries to defend itself (Roman citizens have long ago being replaced by mercenaries in the army), and starts "selling" parts of the Empire in exchange for protection. Eventually, the mercenaries figure out that the "Emperor has no clothes", and overrun and pillage the Empire.
humanity falls back into the Bronze Age (think: eating squirrel meat and living in a cave); 12 centuries of religious zilotry (The Great Inquisition, Crusades) and intellectual darkness follow: science, commerce, philosophy, human rights become unknown concepts until they are rediscovered again during the Age of Enlightenment in 17th century AD.
Regarding the Babylonian civilization (~2,000 BC), we have relatively few records, but we do know that they had a very advanced civilization because we found their legislative code written down on stone tablets (yes, they had laws and tribunals, and some of today's commercial code can even be traced back to Babylonian law). They had child support laws (which seems to indicate that there was a family breakdown), and they collapsed presumably due to a "moral breakdown" figuratively represented in the Bible as the "Tower of Babel" (which was inspired by a real tower). Interesting and controversial anecdote: some claim that the Roman Catholic Religion is nothing more than a rewriting and adaptation of an ancient Babylonian religion!