I love old cemetaries and the older the better. But WHY, when I visit graveyards in churches in England or Scotland (that date back to the 15th Century, for instance) can I not find tombstones that are that old? The oldest ones I ever see date back only to the early 1800’s. Do they keep burying people on top of people or something because of limited space?? Thanks for whoever can answer.
Space is limited, so they dig people up and put them in communal graves, or take their bones and put them in ossuaries. By that point the bodies are mostly no longer rotting, and the relatives of the deceased are either dead themselves or too far removed along the generations to care much. This doesn’t happen as much in the US and other places with more space for graveyards.
A lot of them simply wethered away. Piled up gravestones in Hackney. I’m not sure if you can see the picture, but yes, a lot of people were dug up and reburied with their stones lined up like commuters, but the older stones wether away (you can barely see the date 1759 on the farthest back one, if you can see the picture, but there were more behind it).
Having a tombstone at all is also not that common prior to the 1600s (I’ve seen a lot of tombstones in that era, but not before). Not for poor people, at least. The disestablishment of the church in Henry VIII’s time also meant that a lot of graves and/or their markers were moved.
Many of the churches and graveyards you’ll see that look ancient are also actually Victorian; they might be on the site of an older church, and sometimes they even incorporate parts of the older church, but the main church and its graveyard are newer.
A lot of old churches in Europe have memorial markers inside them that can be several centuries old. Of course, these mostly commemorate members of the ecclesiastical and noble elites rather than the common folk who were buried in graveyards.
How far are you willing to travel? 
Colonial cemeteries and Muslim graveyards and shrines in India have many tombs and grave markers dating back at least to the 17th and 18th centuries.
The did bury people on top of each other when space was an issue.
It may also have something to do with the age. I know that at my hometown cemetery (dating from 1650), the older stones were made of sandstone and wear away badly over time. Also, some graves were probably marked with wooden markers or markers of other materials that can’t stand the centuries.
When I was a kid I discovered a tombstone in our backyard, face-down and used as a step from the patio to the lawn. Though it’s from the early 1800s, it was in excellent condition and completely legible. Since then, it’s been stowed away in the garage. I recently took a look at it, and the lettering has noticeably deteriorated, in spite of being protected by the garage all these years. Time takes a toll, unless extreme measures are taken.
Marble and limestone/cement tombstones don’t fare much better in most towns and cities because acid rain from industrial activity dissolves them. Granite is the only really durable tombstone material, but it wasn’t commonly used most places until relatively recently. I’d imagine pre-industrial tombstones in the UK that subsequently sat through 150+ years of uncontrolled industrial pollution probably wouldn’t be legible any more, if they’re even still recognizable as tombstones at all.
Studying wear on old tombstones is actually fairly interesting: http://www.envf.port.ac.uk/geo/inkpenr/graveweb/gravestone.htm
As others have said, the inscriptions become pretty unreadable over time. There’s a headstone in my town’s churchyard dated 17-something, I think it’s in the 1770s or 1780s, which is pretty well preserved because it is almost hidden under a dense yew tree which presumably shelters it from the elements.
Go see the tombstones in the church (St. Pauls) next door to the World Trade Centre in NYC. Most of the tombstones are pretty much illegible, dating from the 1700’s. The same is probably true of gravestones anywhere in Europe or North America.
As mentioned above, more prominent people got to be buried indoors under church floor paving stones. If you wander the older churches, you can still see markers from the 1600’s and maybe even 1500’s. (Shakespeare’s grave is early 1600’s). At a certain point stones will be the victim of renovations, church disputes (much of the church decorations in England were destroyed by Puritans who felt the were encouraging idolatry) or simple eviction and replacement. Of course, the graves of the royalty are better preserved, but it’s murky who is really in some that date back too far, or have been moved to places of honour.
If you go to Paris, be sure to visit the “catacombs”; the graveyards of most Parisian churches were pretty much emptied into the underground quarries, neatly piled high behind walls of thighbones and skulls with only churches of origin marked. Famous people, even relatives of the kings, are tossed in anonymous heaps. The government spent 2 years after the revolution emptying out “unhealthy” graveyards to reclaim the land.
As mentioned above, many churches had limited space and by the middle ages the practice often was the body rested for a few decades until it was only bones, then those were collected and put in an ossuary so the space could be re-used. Like the catacombs, there’s a ossuary chapel in central Europe (Slovenia?) decorated up the walls and across the ceiling with the bones of monks like a scene out of an H.R. Giger painting. Usually bones were just piled, or boxed, or whatever.
Plus, wood vs. rock - how much effort, how deep would someone carve a tombstone for a common person who had very little assets to begin with?
What is the most durable stone for gravestones? Marble literally melts in the rain. It would have to be hard, but not brittle. I’m thinking basalt.
Like mentioned in that link, granite stones generally fare well. There’s obviously more resilient rocks in nature, but it’s a question of whether a stone is common enough, easy enough to work with, and considered pretty enough for tombstone purposes. I’d say basalt fails on the last count.
That’s the main reason. If graves in graveyards were marked at all, they were usually indicated with wooden grave boards, which soon disintegrated. Gravestones were a specific fashion of the late seventeenth and early eighteenth centuries, which is why, as the OP notes, those are often the oldest ones you find in graveyards in Britain. But, because they were much cheaper, wooden markers remained common until the nineteenth century. It’s just that they mostly don’t survive.
Here in New England, slate gravestones were used from the 1600’s till about 1820 or so. In the local cemetary, the slate stones are still fine-the engraving is sharp and legible. Marble began to be used in the 1850’s-and most of these have illegible markings. From the 1870’s on, the stones have all been of granite-these should last as long or longer, than slate.
I read that you can date the stones quite accurately-by the style of ornamentatyion on them-urns were popular in one era, willow trees and skulls in others.