Have there always been Serial Killers?

[Guardsman Bass]

It probably would have been pathetically easy for a mobile serial killer (say, if he was working as part of a big merchant caravan on a well-traveled route) to kill victims in a paper-scarce society. He could just kill victims in his major stops, and by the time anyone realizes that said persons are missing, he's gone. As someone mentioned above, they'd probably never piece together the string of slayings along the route, and might not care even if they could (if, for example, the murderer is only slaying begging orphan boys on the streets of cities).

[Shroom Man 777]

Conversely, the lack of modern transport technology and modern population densities could hamper serial killing. In an isolated village or so, if you serial killed, it might not take much to find you out and stone you to death. If they suspect you're guilty and put you in a weighing scale with the Bible, or declare you guilty since you float (instead of drown), then you get hanged/stoned/burnt alive.

[Dooey Jo]

They also stems out in their choice of targets. In the medieval ages, who really cared if a peasant or some other low-class person disappeared in the slums? And if they did find someone like that, its unlikely they would talk much about it.

The other low-class persons sure would care, but if it turned out that it was a person from the nobility that had done the killing, the authorities might be hesitant do anything. This was the case with Elizabeth Bathory; the locals knew for years what she was up to, before anyone decided to anything. And even then she was sent to house arrest rather than court, while her servant accomplishes were pretty much executed on the spot, after a "trial". In the small communities of the time, these things really couldn't go unnoticed, as people generally don't like the idea of getting murdered, but an insane peasant would just be executed before he could become a serial killer proper.
This depends, of course, on what region and time you're talking about.

It does seem plausible to me that in different societies, minds would break in different ways.

A disproportionate amount of serial killers do seem to be American. Especially white American men. If this isn't just a statistical artefact, then there probably were not, in fact, as many serial killers in older times as there are now, even if "no-one cared" (which is false, but nevermind that).

[Elfdart]

Another thing I heard put forth was that all those brutal murders that were attributed be the work of some animal or beast in small villages were actually the work of serial killers.

I always wondered if some old monster stories like Beowulf might have started out that way. Grendel was based on some crazy nut who lived in a cave, and as the story was retold he gained more and more inhuman attributes and the stories about his crimes got more and exaggerated. It's not that big of a leap from a hairy dude with a scythe who stabs people to a monster with claws that eats people.

If you look at it that way, the stories of ogres and werewolves start to make sense. Even today we refer to serial killers and pedophiles as "predators" as in To Catch A Predator. The Big Bad Wolf from Little Red Riding Hood is a perfect example. Vicious criminal are routinely likened to wild animals and monsters (rightly so, IMO).

Another thing to keep in mind is that before there were prisons or loony bins, criminals were dealt with in four ways: fine, death, other physical punishment (flogging, cutting off fingers, etc), or being declared an outlaw: run out of the village and forced to live in the woods, swamps, caves or other remote places. Such outlaws were declared "wolf's head", meaning people had a right and a duty to kill them on sight as though the outlaw was a wolf after livestock.

There was a very good article (which I can't find) about how the words warg, or varg and wearh, which are euphemisms for "wolf" come from a root word meaning "strangler" and like the term "wolf's head" were used to describe the most heinous of criminals. Grendel is referred to as a wearh in Beowulf. One thing that I consider a giveaway is the devotion Grendel's mother shows for her son. Grendel wasn't the first outlaw-predator defended by his mother and he certainly won't be the last: Just about every time I turn on the news the police have caught some thug hiding at his mother's house. Or his mother wired him money while he was on the lam, or lied to the police to cover for him. It's quite possible that some thug named Grendel was outlawed, hid himself in a swamp, was aided by his mother and menaced the area until some "hero" came along and killed him and offed his mother for good measure.

[Elfdart]

The other low-class persons sure would care, but if it turned out that it was a person from the nobility that had done the killing, the authorities might be hesitant do anything. This was the case with Elizabeth Bathory; the locals knew for years what she was up to, before anyone decided to anything. And even then she was sent to house arrest rather than court, while her servant accomplishes were pretty much executed on the spot, after a "trial". In the small communities of the time, these things really couldn't go unnoticed, as people generally don't like the idea of getting murdered, but an insane peasant would just be executed before he could become a serial killer proper.
This depends, of course, on what region and time you're talking about.

Nothing like a bunch of angry peasants to mete out swine justice.

It does seem plausible to me that in different societies, minds would break in different ways.

A disproportionate amount of serial killers do seem to be American. Especially white American men. If this isn't just a statistical artefact, then there probably were not, in fact, as many serial killers in older times as there are now, even if "no-one cared" (which is false, but nevermind that).

I think one reason is that serial killers are more likely to be caught by urban police and noticed by neighbors. A sicko living in the backwoods or an isolated suburb has less chance of being noticed, let alone caught.

[Junghalli]

Don't forget those two snipers a few years back...

Also I think that's influenced by the fact that (whatever it may say about our society) the media pays more attention when bad stuff happens to middle-class white people. A serial killer in an inner city slum would be more likely to have his crimes written up to gang warfare, or be relatively ignored by the media if he was discovered because the perception is people get killed there all the time so a few more isn't particularly sensational. "Respectable folks" getting offed gets more attention, and unsurprisingly the serial killers who off them would tend to be of the same demographic.

As others have already pointed out, this is probably another contributing factor to the apparent paucity of past serial killers. Crime was very high in preindustrial times anyway; people would have been more jaded to violent death.

[Zwinmar]

Sargon used to flay people alive then send them to run through the desert, c. 4000 BC (not quite sure on the date)