The vast majority of the world’s oldest, still-standing human-built structures are tombs of one sort or another. (To be fair, this excludes not-still standing structures, like ruins.)
The Wikipedia page on the oldest buildings in the world lists 67 tombs, 11 religious buildings, 9 ruins people lived in (including settlements), 5 used for things like grain storage, and one amphitheater–or 72% of sites built specifically for holding dead people. Additionally, many religious buildings double as tombs–take your typical cathedral with its small graveyard–and we don’t know the purpose of some sites. Stonehenge, for example, contains over a hundred human burials, but we don’t know if Stonehenge was intended as a fancy graveyard, if the people were sacrificed there to sanctify the site, or if it was primarily a religious site at which important people were interred.
The Wikipedia list, alas, is far from complete–it mentions, for example, that over 1,000 Neolithic dolmens (believed to have been ancient burial sites,) have been found in Mecklenburg-Vorpommern, Germany, but doesn’t list them.
Wikipedia claims that there are 35,000 Neolithic and Broze Age dolmens from Korea, constituting 40% of the total–implying a total of 87,500, most of which are found in Europe. The stone circle–and stone ship–tradition in Iron Age Scandinavia was linked to burials. We’re not sure about the 1,000+ British stone circles, but Avebury–the largest stone circle in Europe–like Stonehenge, contained burials. 800 Bronze Age graves called “Giants’ Tombs” have been found in Sardinia; large “Beehive” tombs were built across Greece, southern Europe, and parts of the Middle East.
A tumulus is a mound of earth or stone raised over a grave, ranging in size from small mounds to hills 100 meters wide. Goodness knows how many of them there are; there are over 20,000 in Denmark alone.
Even the great pyramids of Egypt are nothing more than enormous tombs.
In other words, when ancient people died, their relatives–if they had any money–put a remarkable amount of effort into building them enormous, sturdy tombs.
Meanwhile, outside of a few settlements, people don’t seem to have put nearly so much effort into building houses for, you know, people who were still alive and could actually enjoy them.
Folks regularly filled the graves with the deceased’s personal belongings, including wagons, chariots, mummified pets, sacrificed horses, sacrificed wives, sacrificed slaves, food, mancala boards, spinning wheels, jewelry, pots, etc. The ancients believed that you really could take it with you.
I recall one account which noted a particular society that was having trouble accumulating wealth or building up any material development just because every time someone died, all of their belongings were buried with them.
In another account, an Indian chief claimed to have fallen ill and journeyed almost to the land of the dead. On his way back to his body, he encountered a line of deceased villagers, struggling to carry the great quantity of goods they’d been buried with all the way to the land of the dead. Upon waking, he instructed his tribe that the dead had asked to be buried with just the things they could easily carry–a very clever approach to reforming inefficient customs if I ever heard one!
Now imagine King Tut–or Ramses the Great–trying to carry all of that stuff he was buried with to the Egyptian afterlife.
As someone who thinks we should just compost bodies that aren’t being used for organ donation or scientific purposes, I find the whole idea of building giant tombs and filling them with stuff for dead people really weird. How much better off could the Egyptians (and Europeans,) have been if they had devoted of that effort and wealth to building irrigation system, aqueducts, sewer systems, better houses, schools, etc.–or just relaxing–instead of giant tombs for their dead?
But there is some logic to this madness.
Rituals surrounding human interment–whether by water, fire, air, or soil–go back at least 100,000 years, and even the Neanderthals may have buried their dead (also, potentially elephants and chimpanzees.) If there exists any modern or recent human society that does not have some form of rituals surrounding the proper disposal of dead bodies, I have not heard of them. (But maybe this?) Whether motivated by some animist impulse, grief, abhorence of dead things, or respect for the dead, these ritual are important to people.
And outside of communities that practice air burial, people dislike it when stray animals dig up the recently buried corpses of their deceased loved ones and scatter their bones about.
Thus most likely arose the sensible practice of piling rocks atop a grave, both to mark the spot for later mourning (and avoidance) and also to deter the depredations of wild animals.
The more important the person, the more relatives show up at the funeral to pile up rocks and the more importance the tribe places on ensuring that the body is not defiled. So it become a matter of social obligation to create nice cairns for one’s deceased relatives, and a matter of social status to have the biggest cairn.
Next thing you know, your country’s entire economy s devoted to building giant tombs and filling them with stuff.
And then these burial monuments have stuck around for so long because of the taboo against disturbing them–people will happily disassemble an old house for the stones so they can build a new one, but people don’t like disassembling old graves to build houses out of.
Interestingly, though, these kinds of enormous burial mounds seem to have completely died out. Perhaps this is a side effect due to the lack of wolves digging up modern cemeteries.