But aside from the occasional serial killer, you probably don't have too much to worry about. But that's only because of how wonderful our civilization is. And frankly, just how WEIRD it is.
"WEIRD" in this case is a descriptive term that has been adopted by various fields in the humanities. Also, in politics. It's an important reminder: We think of our civilization as “normal,” but it isn't. It's exceptional, in a very literal sense. It's very different from almost any other place and time in history. And yes, I would say it's better. Cannibalism is one of those reasons.
National Geographic just came out with an article on the history of cannibalism where they point out just how widespread it was throughout history. I'd actually say there's a couple of places they were playing softball, but more on that later.
If you're a normal member of our WEIRD civilization, you probably think cannibalism is grotesque and horrific. Why would anyone do it? Outside of serial killer-style mental illness, there are two reasons: Survival and culture.
Survival cannibalism could happen to anyone, when put in an extreme condition. People are starving to death and have no choice. It happened to a Uruguayan Rugby Team when their plane crashed in the Andes Mountains in 1972. Sixteen survivors of the crash were trapped in the freezing mountain for 72 days and were forced to eat the frozen flesh of the corpses of the dead passengers to survive.
People in a situation of survival cannibalism aren't doing it because they want to – and if they survive the harsh conditions, they won't return to it. Usually they find their choice horrific and have a lot of trouble living with it after.
Cultural cannibalism is totally different, even if in some cultures cannibalism is something that only happens in extreme situations (war or famine). Cultural cannibalism is where the social taboos are such that they have socially-mandated situations where it's OK to eat people.
In the NatGeo article, the author tries to make it sound like the first Europeans to come to America used "cannibalism" as an excuse to enslave the natives. He makes it sound like there wasn't any actual cannibalism happening.
The Aztecs and associated people would perform ritual sacrifice, you probably know that part already. But part of that ritual involved cutting up and eating parts of the victims. Who got to eat which parts was ritually important, and based on social class. This wasn't eating human flesh to avoid starvation. It was for a different purpose (religious, in this case).
It wasn't just them. The Mohawk got their name from the Algonquin word for "flesh eater," although it seems that they later abandoned ritual cannibalism. The Anasazi and Karankawa people were also ritual cannibals. Various Amazonian tribes would eat their dead as a funerary rite. Other South American tribes may have engaged in cannibalism of captured enemies.
The Maori and various Polynesian tribes were cultural cannibals, eating their dead, their enemies or both. In Africa, a number of tribes in different areas engaged in cultural cannibalism. Not all of this is in the distant past. In the 1980s, Doctors Without Borders presented evidence to Amnesty International of ritualized cannibalism taking place in Liberia; it was subsequently covered up for political motives.
Various African dictators engaged in cannibalism, including Jean-Bedel Bokassa and Idi Amin. This wasn't just because they were nuts, though that was part of it. It was because they were tapping into ancient ritual ideas from their culture. To eat another person was a show of power, and in cultural cannibalism when you eat someone you gain their life-force.
While cannibalism is something that has existed since the stone age, don't assume it's just very primitive cultures that practice it. Other advanced civilizations have done so too.
In India, which has had an advanced and sophisticated civilization for thousands of years, cannibalism is considered extremely taboo. But in certain very specific contexts, there's exceptions.
For example, the Aghori monks are a type of Ascetics who worship Shiva. They seek to escape the bonds of normal human consciousness by breaking all taboos and restrictions. They'll go around naked, smoke drugs, live in funeral grounds, and drink out of skulls – all things that are taboo for Indian culture, especially for most monks. They also eat the flesh of the dead. In spite of breaking all these rules, the Aghori are considered powerful holy men in Indian society, said to have dangerous powers.
China has the longest single continuous civilization on Earth. They've accomplished all kinds of amazing things and have many admirable qualities. But they had a long tradition of cultural cannibalism. The upper classes in ancient times would eat human meat in the belief it could prolong life or heal illness. Chinese Eunuchs would eat young boys to maintain virility. As late as the 19th century, it was common for Chinese executioners to ceremonially eat the hearts of those they killed, and sometimes make stews or steamed buns with the meat or blood of their victims.
And while Western influence in the 19th century gradually caused cannibalism to fall out of favor, even in 2004 there was still a case of a Chinese man stealing corpses to make medicinal soup for his sick wife.
There were also cannibalism reports during Maoist China, to survive mass starvation caused by failed communist policies. It was survival cannibalism, but was also less taboo because of culture.
In the West, cultural cannibalism may have been practiced by the ancient Celts; there's evidence from bones that as late as 2000 years ago that still happened. But Greco-Roman civilization and Judeo-Christian religion considered it abhorrent, and cultural cannibalism was wiped out. The combination of Greco-roman concepts about rule of law and the Judeo-Christian principles of the universal worth of every individual gradually led to the development of a very different understanding of "human rights" than most other civilizations, even other advanced ones. These are the same principles that led to ideas like "all men are created equal" and treating liberty as an inalienable right. The decline in cannibalism worldwide coincided with the expansion of Western values (even if sometimes it was through very brutal colonialism).
The reason Westerners aren't cannibals is definitely not because there's something special about us compared to other human beings. It's just about our civilizational values. If those were ever to go away, there's nothing to say you wouldn't end up your neighbor's lunch.