Ideocide is the intentional extinction of an idea or a way of thinking. Related concepts are ethnocide and civicide, the intentional cessation of an ethnicity or civilization. All three are intentionally distinct from genocide, the intentional killing of a people, in that they go to the death not of human beings, but of ways that human beings live.
Mostly, these terms have been used derisively by critics of globalisation on the radical left. At the moment, anyway, my interest is with the history of these events historically, and I am only secondarily interested in the intentions of those who bring these events about. In other words, I am interested in what causes ideas, ethnicities or civilizations to cease to exist.
The Rise and Fall of Polytheistic Paganism
One of the most striking of these events, and a favorite subject for English Romantic poets, is the death of polytheistic paganism outside Hindu India and a handful of other communities around the world (some with source populations from India, and others outside that tradition such as the Mari people of Russia). We know a fair amount about how the pagan religions of Europe and the Mediterranean came to cease to be practiced because it happened in the historical era.
The Roots of Polytheistic Paganism
The fact that this kind of paganism apparently wasn't practiced in sub-Saharan Africa, or further East than India (the exception that proves the rule, Hindu religious practice in Bali, dates from the 1st century CE), lends support to the argument that the proto-Indo-Europeans, and the proto-Semites (the people who languages ultimately gave rise to both Hebrew and Arabic), were polytheistic pagans, and that polytheism was probably developed in the Middle East.
Evidence of proto-Hindu religious practice dates to the pre-Indo-European farming people of the Indus River Valley (now mostly in Pakistan), as far back as 3300 BCE, which coincides with the oldest historical records of polytheistic Egypt and Sumer (in what is now Southern Iraq). The Middle Eastern origins of some of the domesticated crops used in the Indus River Valley civilization, and the stronger links that both Dravidian and the Indo-European languages of India have to languages with Middle Eastern origins than to languages spoken further to the East of India, suggests that the people of India who practiced polytheism had Middle Eastern roots.
The absence of polytheistic paganism in the people who farm crops originally domesticated in what is now the Sahara desert, before it was dessicated, suggest that polytheistic paganism arose after the Sahara desert formed. This started to happen around 4000 BCE.
This puts the likely date for the development polytheism very close in time to the time of the first written records and the first know kings in human history, about six or seven millenia after the Neolithic Revolution, sometime between 4000 BCE and 3300 BCE, as noted before, probably somewhere in the Middle East or closely adjacent to it (perhaps Anatolia, Southwestern Iran or along the Nile).
The evidence indicates that the people of Southeast Asia and East Asia, who did not develop polytheism in the way that the people of Europe, North Africa, the Near East and India did, independently developed agriculture around the time of the Neolithic revolution; their shared ties to the first modern humans to leave Africa for the Middle East (probably around 100,000 BCE) pre-date the Neolithic revolution (around 11,000 BCE).
We also know that the ancestors of the Native Americans, who are not polytheistic (with the possible exception of Gods of the early farming empires), left Asia for the Americas sometime after the domestication of the dog (25,000 BCE to 15,000 BCE), and before any plants or animals were domesticate (around 11,000 BCE) by which point rising sea levels isolated them from Eurasia for more than ten millenia.
And, we know that the ancestors of the indigeneous people of Australia, who are not polytheistic, arrived there around 50,000 BCE and were isolated from the rest of the world, with very minor exceptions that left little impact other than the introduction of the dingo to Australia from a small founding population, until the 19th century.
The Transition To Monotheism
The Hebrew Bible is predominantly a story of the transformation of the Jewish people from polytheistic pagan and animist beliefs to monotheism in the area from Babylon to Egypt over a period of about fifteen hundred years. It describes the Jewish people as a people surround by and persecuted by polytheistic pagans from the time that the Jewish people made a covenant with their God until the Hebrew Bible's narrative ends.
While the Hebrew Bible is hard to view as an entirely factual historical account (it differs with other historical records in some particulars, is ambiguous in other particulars and describes events that are implausible or fantastic in yet others), there is good reason to believe that there was a largely monotheistic kingdom or pair of kindgoms made up of Hebrews for a significant part of the first millenium BCE.
The principal scriptual source for Muslims, the Koran, likewise makes clear that the Arab peoples who formed the initial core of Muslims in the 600s, were also predominantly polytheistic pagans prior to adopting Islam.
The Rise of Monotheism
There is some evidence for a brief period of monotheistic or near monotheistic religion arising from Egyptian polytheism for the life of one or two rulers in Egypt at a time when some of the ancient Hebrews may have lived there or been in contact with Egypt.
There is no evidence of other major monotheistic religions in the Middle East in this era, although the dualistic Zoroastrian religion, with its roots in Iran, was encounted by and probably influential in the religious beliefs of Jews exiled in what is modern day Iraq in the period after the Hebrew bible ends and before the destruction of the Jewish Temple in Jerusalem by the Romans in 70 CE.
Christianity as an organized religion didn't come into being until the middle of the first century CE, and was not very prominent in Roman society for another century. The destruction of the Temple gave rise to the Jewish diaspora and Judaism in its modern Rabbinic form, and the formative periods of both Christianity and Rabbinic Judaism were contemporaneous. There would be no Jewish communities larger than villages or neighborhoods in a large non-Jewish city again until the rise of Israel in the 20th century.
The End of the Pagan Era
Prior to Roman Emperor Constantine's decree legalizing the practice of Christianity on a basis remarkably similar to the American First Amendment protections for religion, the religious ethos organized around multiple dieties was the state religion of the Roman Empire. The Greeks, the Egyptian Coptic civilization, the Sumerians, the Norse and India's Hindus all had comparable religious systems with different dieties in each case.
Less than two hundred years later, not long before the Western Roman Empire fell to barbarian invaders, the Roman Empire banned polytheistic pagan practice and vigorously rooted it out, enacting civil forfeiture laws to dispossess people of property used for pagan practice, destroying pagan texts, and making it a crime to conduct pagan religous practice. The late Roman Empire also sought to stamp out heretical Christian doctrines (mostly Arian doctrine and to a lesser extent Gnostic Christian beliefs which had already been greatly marginalized in the Western Roman Empire). By the time that the empire fell, living pagan religous practice was all but dead. The former Romans, and many of the barbarian invaders closest in space to the former Western Roman Empire, as well as essentially all of the residents of the Eastern Byztantine Empire (it would not acquire the name until later), were at least nominally affiliated with some branch of the Christian faith or were part of a small Rabbinic Jewish diaspora.
Starting about a century after the fall of Rome, and continuing for about two centuries after that the Islamic Empire expanded dramatically. It grew to include much of the former Roman and Byzantine Empires including the Levant (which made up much of the Southern half of the Byzantine Empire), the North African coast, and Iberia (the penninsula that is home to modern Spain and Portugal).
The Islamic empire tolerated Jews and Christians as "people of the book" and spiritual ancestors of Islam, but like the Roman Empire in its last century or so, banned and punished polytheistic pagan practice.
The Islamic empire ultimately broke up, but all of modern day North Africa, the modern day Middle East (outside Israel and a few pockets of Christianity in the Levant), Turkey and parts of the Balkans remain overwhelmingly Muslim, and have been predominantly Muslim without interruption other than a few brief periods of Crusader rule in the Levant in the Middle Ages. Polytheistic paganism has never resurfaced in any of these territories before the advant of late 19th century and 20th century neo-paganism.