Samhain, All Hallows Evening. Hallowe'en, Halloween. The name has changed but the world’s fascination with a day of spooks and scares has never wavered. Except it has also always been about harvests and farming and food.

It may seem odd to lump together food and ghosts but that is Halloween in a cultural nutshell; a confusing mash-up of cultures and beliefs. That is actually a good thing. It is evidence for how creating melting pots of people who become one community is better than a salad bowl where no one wants to include outside groups in their customs.

It took thousands of years but Halloween is now incredibly popular. If you saw the number of Halloween t-shirts in my storage bins, you’d know it is big business, and not just for clothing. In America alone it is an $8 billion market segment, which means Halloween is only surpassed by Christmas in spending. That spending is on lots of different things. Despite people associating Halloween with kids and treats, candy is only 15% of the revenue. The rest is adult costumes and parties and decorations.

Decorations like, oddly, pumpkins.

The United States alone will produce 1,000,000,000 pounds of pumpkins, and nearly half of them will come from a place few can guess; Illinois. Its warm, dry summers and arable soil are ideal for pumpkins and pumpkins are how food processing company Libby's, which makes canned pumpkin pie filling, turned the town of Morton, Illinois, with just 17,000 residents, into the pumpkin capital of the world.

That’s right, California can claim to be the World Leader in Garlic and Pistachios, but The Land of Lincoln dominates when it comes to autumn’s favorite orange squash.

Why pumpkins? The only explanation is that cultural evolution, like biological, happens in fits and starts and makes detours, and it can tear down or build up. How a niche celebration in old Celtic lands became the second most popular holiday after Christmas across a vast ocean doesn’t have to make any logical sense, because it happened anyway.

When the Roman Republic invaded Albion, what is now called England(1), they were not the first conquerors. The Celts had preceded them by a thousand years, and the Celts there celebrated their New Year, the end of the harvest and the beginning of the cold, dark days of winter, on November 1st. They called it Samhain.

The night before Samhain, their New Year’s Eve, was a night in which they believed spirits got one last opportunity to get revenge on anyone who had slighted or harmed them during life. Celts, like Scots now, were quick to love but when slighted they held a grudge for so long the great grandkids will have forgotten why(2), but will still honor it. To prevent grudges by recent spirts from harming their family members on the last night before the dead went to the afterlife, Celts painted faces on gourds or carved “neep lanterns” - turnips - to scare them off. Other supernatural beings might dress as beggars and knock on doors asking for handouts. Lore said if you had the misfortune to have one knock on your door and you refused to feed them, mischief was likely to result.

You can see where all of that still exists today, in tricks or treats.

The Romans were animistic, they believed everything had a spirit, and they wisely had a policy that made a docile people remain calm; they let those under new Roman control keep their religion and their weapons. That gave the new subjects a feeling of freedom and they didn’t rebel.(3) To make Roman culture even more palatable to new people, they often showed how their traditions were similar. This assimilation was their approach in many ways, including religions. Pax deorum, peace with the gods, was a guiding belief, so adding a few more Gods to placate those in new lands was not difficult.

By the 500th year of the Roman Republic, they had conquered a lot of different areas, from the Balkans and the mid-east to what they named Britannia, which meant a lot of different cultures, a lot of different gods, and festivals to match. Since Samhain fell during the festival that honored Pomona – a goddess of fruit - at least according to the Legate that governed the new island – the Romans said they too celebrated and agreeable Celts gradually expanded Samhain to include Roman harvest concepts. Now the holiday had ghosts appearing, faeries playing tricks if you didn’t give them treats, and apples.(4) A real monster mash of traditions.

Hundreds of years later, the Celtic Albion that had become Roman Britannia was transformed again, into Anglo-Saxon “Englaland”, but the November 1st Samhain tradition remained. During those so-called Dark Ages, Pope Gregory III wanted less pagan imagery in the west so he moved the date of All Hallows Day - Hallow is another term for Saint - from the spring to Samhain. It didn’t change the tradition much. Rather than going door-to-door dressed as beggars on "All Hallowes Evening”, boys dressed up as saints and knocked on doors and requested alms for the poor – they were the same beliefs using different costumes. Sometimes that is good enough.

By the 1500s kids spent All Hallowes Eve, shortened by the Scottish  to Hallowe'en, a spelling that still existed in writing of just a few decades ago,(5) going “a-souling", where they would visit nearby homes and be given ale or food, sometimes even money,  in return for prayers for the souls of the family. Hallowe'en had become so common that by the end of the century, Shakespeare referenced it.  He loved spooky stuff, even in comedies like “The Two Gentlemen of Verona.”  

Shortly thereafter the  danse macabre, first created as an allegory of ‘dancing to death’s tune’ in France during the Black Plague, became popular and it was just what it seems; a carnival of the dead, though a lot less light-hearted than the modern Mexican Día de Muertos (“Day of the Dead”), which has candy skulls and even Pan de Muerto, bread of the dead.

In the 1700s and early 1800s is when Halloween really arrived in America. The Puritan culture of those religiously disenfranchised by Europe had given way to a large influx of Scots looking for land and prosperity after the Act of Union with England(6) and then when onerous lease terms for Irish farmland led to hunger and famine in the 1800s, an even larger wave of Irish immigrants followed.

Scottish women had brought with them a tradition of staring into a mirror with a candle at midnight to see if the face of their future husband was revealed but that’s not really a community event. The Irish arriving in America lit a new spark there. They also loved carving faces into turnips, but turnips could still, with challenges(7), be turned into food, while pumpkins got less culinary respect. Since they were more expendable, pumpkins were more available for decorative carving. 

The Irish tackled those at Halloween with fonn – gusto - and suddenly there were a lot of Irish in America. Around a million new arrivals just in the 1840s.

Unlike Scottish painted faces to scare off spirits, the Irish “neep lanterns” were said to evoke the ghostly lights that appeared over peat bogs in the old country. Those lights were called will-o’- the-wisps but the carved root vegetables were jack-o-lanterns, named such for Stingy Jack, who tricked the devil into agreeing that Jack would never go to Hell. Unfortunately for Jack, he had also committed far too many sins to get into Heaven, so he was doomed to purgatory. His only companion for eternity was a hollow turnip and a lump of coal the devil tossed him for light.

That Irish tale delighted their fellow Americans and soon enough carving pumpkin jack-o-lanterns and putting candles inside for Hallowe’en spread across the country. It got so popular Catholics and Protestants finally found something to agree on; putting the October holiday on the calendar.

By 1900, Halloween had evolved again. Parties became common while grotesque costumes and religious overtones began to fade in popularity. Modern gatherings focused on games, food, and fun events. During the first half of the 20th century, Halloween became a completely secular event that involved neighborhoods, communities and cities, with parades and trick-or-treating nationwide.

This year, 40 million Americans will dress up as a Ghostbuster or Captain America or something else, following thousands of years of tradition. It will mean $2 billion in candy sales, which you might expect, but what you may not expect is which U.S. state will lead in trick-or-treating per capita.

It’s Utah, followed closely by Alaska.

Now Halloween has become a fixture of popular culture and along the way we acquired even more symbols.

So many that just the science can fill an entire book. Let’s start by discussing some ways in which Halloween even shaped science discovery. Everyone has heard of “spooky action at a distance” to describe quantum entanglement. Even the Big Bang is related to Halloween.