Ritual bathing has been part of the Jewish religion for centuries, far before the tradition of Christian baptism was even though of. As the Biblical Archaeology Society reports, a dedicated ritual bath, known as a mikveh or mikvah, was uncovered in a Jerusalem excavation that dates back to a period spanning 538 BC to 70 AD. Visitors to the mikveh would have immersed themselves in collected rainwater, an important feature developed in accordance with religious law demanding ritual baths be taken in “living” water taken directly from a natural source, like a river or spring.

Mikvehs are still used in some Jewish communities to this day. The Jewish Women’s Archive explains that women in modern Orthodox communities often use mikvehs to ritually purify themselves after menstruating or giving birth. In some places, the highly gendered nature of this practice, which hinges on the ritual impurity of a woman’s body, has made it controversial and subject to a number of modern reinterpretations. The Washington Post notes that men may also use the mikveh on occasion, such as before important rituals or holidays, and that converts to Judaism may also choose to undergo a mikveh ritual to mark their transition.

Though it’s mentioned in the Gospels and has since become a pretty big deal for many churches and their congregations, baptism doesn’t appear to have reached prime importance until the 1st century AD, according to Britannica. Before then, the history of Christian baptism is quite a bit murkier, with some hints that it was a common ritual with widely varying particulars.

The exact details of how baptism was supposed to happen and whether it was necessary to become a Christian were topics of great discussion and, inevitably, argument. Even today, Britannica notes that historians can’t clearly tell if it was considered absolutely necessary to become a Christian, or if it was only meant to reflect a more profound inner transformation.

We can at least be reasonably sure that baptism was widespread by the time of Paul, the devoted Christian convert and apostle who widely preached and founded numerous Christian enclaves in the wake of Jesus’ crucifixion (via World History Encyclopedia). Though Paul was such a big deal that many modern scholars now credit him as one of the true founders of Christianity, he wasn’t quite so focused on baptism as you might think. According to Interpretation: A Journal of Bible and Theology, baptism was important, but perhaps not key to Paul’s zealous mission. It’s sometimes even a minor detail to him, to the point where he doesn’t quite remember who he’s baptized.

Since it was eventually considered such a big step in becoming a Christian and member of a church, just how baptism was supposed to happen generated plenty of controversy. For some, an incorrectly performed baptismal ritual could put someone’s very salvation in danger, so getting it right was of key importance. “History of Christianity” notes that, for some early Christian churches, it was possible that a bishop who performed baptisms could put his whole flock in danger if he wasn’t perfectly pure. It may as well have been the Devil who baptized someone, some seemed to say.

People argued about details like triple immersion, representative of the Holy Trinity, and whether or not it was okay to simply pour water over someone while reciting the names of said trinity (via “Baptism in the Early Church“).

Given all of the opportunities for argument and the seeming life or death nature of the questions, many church splits happened as a result of disagreements over baptism. According to Encyclopedia.com, much of the history of Christianity is marked by breakaway sects who often declared that they were the true church and were practicing the right kind of baptism. Some, like the Anomoeans, rejected the full triple immersion ceremony, while the Arians required that prospective members get re-baptized before joining their church. Both also argued that baptism didn’t immediately confer God’s grace upon a person, especially if the baptizing minister wasn’t up to snuff.

Generally speaking, there are three types of baptism that a person can encounter: immersion, affusion/pouring, and aspersion/sprinkling. Per Owlcation, immersion generally involves a full or partial dip into a body of water, whether it’s a natural feature or a man-made pool. It appears to have been the most common practice in the early Christian church, if it wasn’t outright the only way to get baptized then.

Affusion, where water is poured on top of a person, reached its height of popularity in the early Middle Ages, around the 10th century in most places in and near Europe. Aspersion, where a small amount of water is sprinkled on a person’s head, has often proven to be the most convenient method for people who can’t manage a full immersion. Aspersion and affusion are the types of baptism you’re most likely to encounter at a child’s christening, though some churches like the Orthodox church will fully immerse infants in a symbolic imitation of Christ’s death and rebirth (via Russia Beyond).

The type of baptism someone experiences depends largely on their church and faith traditions. Denominations that almost exclusively practice adult baptism tend towards full immersion, while those that make room for infant or child baptism tend to make room for less overwhelming methods.

Beginning in the 16th century, one rather large segment of Christians began to draw away from infant baptism, creating a rather intense breakup within the church — though, of course, said church had already seen its fair share of anxiety and discord around baptism alone, not to mention any number of other theological quandaries. Still, this particular break proved to be one with some seriously long-lasting consequences for believers that can still be seen and felt today. Enter the Anabaptists.

Specifically, according to Encyclopedia.com, it was in 1517 that many people began to push back against infant baptism. The only way to properly become a Christian, they said, was to fully and consciously choose to do so once one was an adult. Children, they argued, couldn’t fully comprehend the meaning of Christ’s sacrifice and weren’t yet ready to join the church. Collectively, these dissidents became known as Wiedertäufer or Anabaptists, for their insistence that adults wanting to join in the growing religious movement had to be rebaptized first.

Many Anabaptists were, unsurprisingly, subject to persecution, and some of their more vehement early leaders were even executed, per Britannica. Yet, the movement persisted and communities of Anabaptists (which also often preached other principles like communal living and egalitarianism) proliferated. Modern Anabaptists include the Hutterites, Mennonites, and Amish (via PBS), and you can also reasonably make the case that modern Baptists are theological descendants of this group, too.