Not quite Forgotten Treasures: Part 2, Cahokia

Illustration of Cahokia Mounds, Illinois

It took almost 400 years between Columbus’s arrival in the New World and the complete military domination of the USA by the invaders–but it happened.

The Americas before Columbus arrived were a place of amazing contrasts–from the igloo-dwelling, hunter-gathering Eskimo to the literate, city-building, cannibal Aztecs. At the southern tip of of Patagonia lies the Tierra del Fuego–so named because the nearly naked locals opted to cope with their frigid climate by carrying fire everywhere.

The oldest still-occupied towns in the US are the Acoma and Taos Pueblos of New Mexico, built nearly a thousand years ago (though today the vast majority of residents live in newer housing with electricity and running water built nearby the historic pueblos.) But the oldest overall is Cahokia, occupied between 600 and 1400 AD:

Cahokia was the largest and most influential urban settlement of the Mississippian culture that developed advanced societies across much of what is now the central and southeastern United States, beginning more than 1000 years before European contact.[5] Today, Cahokia Mounds is considered the largest and most complex archaeological site north of the great pre-Columbian cities in Mexico. …

Cahokia became the most important center for the peoples known today as Mississippians. Their settlements ranged across what is now the Midwest, Eastern, and Southeastern United States. Cahokia was located in a strategic position near the confluence of the Mississippi, Missouri and Illinois rivers. It maintained trade links with communities as far away as the Great Lakes to the north and the Gulf Coast to the south, trading in such exotic items as copper, Mill Creek chert,[13] and whelk shells.

Mill Creek chert, most notably, was used in the production of hoes, a high demand tool for farmers around Cahokia and other Mississippian centers. Cahokia’s control of the manufacture and distribution of these hand tools was an important economic activity that allowed the city to thrive.[14]Mississippian culture pottery and stone tools in the Cahokian style were found at the Silvernale site near Red Wing, Minnesota, and materials and trade goods from Pennsylvania, the Gulf Coast and Lake Superior have been excavated at Cahokia. Bartering, not money was used in trade.[15]

Although it was home to only about 1,000 people before c. 1050, its population grew rapidly after that date. According to a 2007 study in Quaternary Science Reviews, “Between AD 1050 and 1100, Cahokia’s population increased from between 1400 and 2800 people to between 10,200 and 15,300 people”.[16] an estimate that applies only to a 1.8 km2 high density central occupation area.[17] Archaeologists estimate the city’s population at between 6,000 and 40,000 at its peak,[citation needed] with more people living in outlying farming villages that supplied the main urban center. … If the highest population estimates are correct, Cahokia was larger than any subsequent city in the United States until the 1780s, when Philadelphia’s population grew beyond 40,000.[18]

Monk’s Mound, Cahokia

Like many early cities, Cahokia has distinctive, flat-topped pyramids, (here called “mounds”)–probably not because pyramids are magical or because the Cahokians were in contact with Egyptians or aliens, but because it’s the easiest large shape to build. The Cahokians lacked good stone build with and draft animals to haul materials over long distance, so Cahokia’s 120 mounds were built largely of compacted earth:

To achieve that, thousands of workers over decades moved more than an “estimated 55 million cubic feet [1,600,000 m3] of earth in woven baskets to create this network of mounds and community plazas. Monks Mound, for example, covers 14 acres (5.7 ha), rises 100 ft (30 m), and was topped by a massive 5,000 sq ft (460 m2) building another 50 ft (15 m) high.”[4]

Monks Mound is the largest structure and central focus of the city: a massive platform mound with four terraces, 10 stories tall, and the largest man-made earthen mound north of Mexico. Facing south, it is 100 ft (30 m) high, 951 ft (290 m) long, 836 ft (255 m) wide and covers 13.8 acres (5.6 ha).[24] It also contains about 814,000 cu yd (622,000 m3) of earth.[14] The mound was built higher and wider over the course of several centuries through as many as ten separate construction episodes, as the mound was built taller and the terraces and apron were added.[24]

Since the mounds are made of dirt and it rains in Illinois, erosion is an issue.

Excavation on the top of Monks Mound has revealed evidence of a large building, likely a temple or the residence of the paramount chief, which would have been seen throughout the city. This building was about 105 ft (32 m) long and 48 feet (15 m) wide, and could have been as much as 50 ft (15 m) high. It was about 5,000 sq ft (460 m2).

A large flat plaza located adjacent to Monks Mound was a place where games and public rituals took place.

Reconstructed piece from Etowah Indian Mounds, Georgia

The Cahokians (and Mississippians in general) had mastered the art of copper working, producing fine ritual art like the dancing warrior to the left. Copper can be worked and shaped while still cold; the Mississippians had not learned how to make bronze nor smelt iron.

The Cahokians also built a Stonehenge-style “Woodhenge”:

a ceremonial area with a 412 feet (126 m) in diameter circle of 48 upright wooden posts.[1] Archaeologists date the placement of at least one of the posts to approximately 950 CE.[2] Archaeological research has shown that four of the posts were at the cardinal locations of north, south, east and west, the eastern and western posts marking the position of the equinox sunrise and sunsets. Four other posts in the circle were shown to be at the summer solstice sunrise and sunset and the winter solstice sunrise and sunset positions.

Woodhenge, Cahokia

If you make your sundial big enough, it can double as a clock–a useful trick for a society with a priestly class that wants to do special ceremonies on specific dates.

Woodhenge was eventually dismantled (and moved elsewhere), and the site converted to a cemetery. Some of the burials were of wealthy individuals–perhaps rulers–but most appear to be victims of mass human sacrifice:

A large rectangular pit was dug into the southeast corner of the mound and a mass burial of 24 women was made in it….

A small platform was constructed near the southeastern ramp and four young males with their arms interlocked and missing their hands and skulls were laid out on the platform.[6] Some researchers have concluded that the four men may represent the four cardinal directions.[11]

In a pit excavated next to these four men were placed the bodies of a large group of young women. This mass grave contained the remains of 53 females ranging in age between 15–30 years of age, arranged in two layers separated by matting.[4][6][8] The young women show evidence of having been strangled before being arranged in neat rows in the pit.[11] Analysis of bones and dental traits of these women have led archaeologists to believe these individuals were not from the same social class and ethnic group as other individuals interred in the mound. …

Next to this mound to the southwest another mass burial was made.[4] This burial is the most grisly found at the site, containing 39 men and women who appear to have been violently killed. … The victims were then killed and thrown over the edge of the pit. These people showed signs of meeting a violent end, including several being incompletely decapitated, some with fractured skulls and others with fractured jawbones.[6] The evidence shows that some of these individuals were buried alive: “From the vertical position of some of the fingers, which appear to have been digging in the sand, it is apparent that not all of the victims were dead when they were interred – that some had been trying to pull themselves out of the mass of bodies.”[4] The presence of arrowheads in the back of some of these victims, coupled with the beheadings and other evidence of violent death, has led some researchers to conclude that these victims show evidence of warfare or were even the losers of a rebellion against the rulers of Cahokia … On top of them were the remains of 15 elite individuals laid out upon litters made from cedar poles and cane matting .[6] Radiocarbon dating of the cedar poles used for the litters in the top layer burials in this pit determined that this burial was made approximately 100 years after the woodhenge circle had been constructed, or in approximately 1030 CE.[4]

Lovely people.

Since the Mississippian culture had not entirely disappeared by the time European chronicles arrived in the area, we actually have an account of a royal Mississippian burial accompanied by ritual sacrifice. According to Wikipedia:

Upon the death of “Tattooed Serpent” [of the Natchez,] in 1725, the war chief and younger brother of the “Great Sun” or Chief of the Natchez; two of his wives, one of his sisters… his first warrior, his doctor, his head servant and the servant’s wife, his nurse, and a craftsman of war clubs all chose to die and be interred with him, as well as several old women and an infant who was strangled by his parents.[14] Great honor was associated with such a sacrifice, and their kin was held in high esteem.[15] After a funeral procession with the chiefs body carried on a litter made of cane matting and cedar poles ended at the temple (which was located on top of a low platform mound); the retainers with their faces painted red and accompanied by their relatives dressed up in their finest garments, were drugged with large doses of nicotine and ritually strangled. Tattooed Serpent was then buried in a trench inside the temple floor and the retainers were buried in other locations atop the mound surrounding the temple. …[14]

Artsist’s conception of Watson Brake

Cahokia is only one of the Mississippian people’s many settlements–at least 85 similar sites have been discovered, and that’s just the Mississippians. Other cultures also built mounds, such as the Watson Brake site in Louisiana, built around 3500 BC. (Perhaps these were really all the same culture, but archaeologists classify them as different ones.) The Mississippian sites are generally distinguished by:

  1. Earthen pyramids or mounds
  2. The development of large-scale, corn-based agriculture
  3. Shell-tempered pottery
  4. Large trade network extending from the Rockies to the Atlantic, Great Lakes to the Gulf of Mexico
  5. Social hierarchy and centralization of political power, with cities like Cahokia dominant over smaller towns
  6. A particular style of art and artifacts, reflecting Mississippian religious beliefs and lifestyles

Though Cahokia itself was abandoned around 1300 AD, Early European explorers such as Hernando de Soto encountered other Mississippian peoples and made records of them:

De Soto observed people living in fortified towns with lofty mounds and plazas, and surmised that many of the mounds served as foundations for priestly temples. Near present-day Augusta, Georgia, de Soto encountered a mound-building group ruled by a queen, Cofitachequi. She told him that the mounds within her territory served as the burial places for nobles.

But like Etzanoa, by the time the Europeans returned, the settlements had been abandoned, most likely due to diseases caught from the French and Spanish.

the big 6 (part 4: Norte Chico, Peru)

4. Norte Chico (Peru):

(Note: I cropped the photo, so the river is no longer visible) Photo from “Real History of the World,” but it also appears on a billboard at the site itself, so photo is legit.

According to Wikipedia,

The Norte Chico civilization (also Caral or Caral-Supe civilization)[1] was a complex pre-Columbian society around 3500BC-1800BC that included as many as 30 major population centers in what is now the Norte Chico region of north-central coastal Peru. Since the early 21st century, it has been established as the oldest known civilization in the Americas.

Picture 4We can debate about whether or not Egypt, Mesopotamia, and even the Indus Valley culture really arose independently of each other, but there’s no doubt that Norte Chico, the first known civilization in the Americas, arose all on its own.

Norte Chico is a pre-ceramic culture of the pre-Columbian Late Archaic; it completely lacked ceramics and apparently had almost no visual art. The most impressive achievement of the civilization was its monumental architecture, including large earthworkplatform mounds and sunken circular plazas. Archaeological evidence suggests use of textile technology and, possibly, the worship of common god symbols, both of which recur in pre-Columbian Andean cultures. Sophisticated government is assumed to have been required to manage the ancient Norte Chico.

From Ritual is Power, an archaeologist’s blog about Norte Chico

Norte Chico is located in a north-central area of the coast, approximately 150 to 200 km north of Lima, … It comprises four coastal valleys: the Huaura, Supe, Pativilca, and Fortaleza; known sites are concentrated in the latter three, which share a common coastal plain.

Unfortunately for me, Wikipedia doesn’t have much on Norte Chico; it looks like a lot of the discoveries are relatively recent and so haven’t yet made it into the article. This means I’ve had to dig through other sources, some more reliable (Peru Reports) than others (“dolphin space aliens built ancient pyramids in Peru!”)

I’m doing my best to get information from the more reliable sites, but forgive me if I mis-remember some speculation as fact.

Caral, Peru
Caral, Peru

Like Egypt and Sumer–but unlike the Indus Valley–the people of Norte Chico built monumental architecture (notably, pyramids, in much the style that you’d expect if you’ve ever seen a picture of a Mesoamerican pyramid, though their great age has rather reduced their grandeur.)

The Norte Chicoans built their pyramids by creating a large square wall of mortared stones, and then filling in the center with rocks transported in woven bags. (Given the state of the Norte Chicoan pyramids, despite the lack of inclement weather in the area, I suspect the Egyptian methods stand up better over the millennia.)


I suspect that early civilizations tended to build pyramids not because they were all secretly in contact with each other, but because if you want to add a second, third, or fourth story to a building, everything is less likely to fall down if you move each layer in a step. This results in the famous “step pyramid,” like those of the Mayans, Aztecs, early Egyptians, and Norte Chicoans. (Only the Egyptians, to my knowledge, went on to build real pyramids–ie, pyramids with smooth sides.) In other words, pyramids are just the easiest way to make a big building out of stone.

The Norte Chicoans used irrigation to raise corn, sweet potatoes, and other crops, plus they fished for anchovies. They also raised cotton, which appears to have been domesticated almost simultaneously in both the Indus Valley and Norte Chico.

huanca stones
huanca stones

I have also seen references to these intriguing stones–the huancas?–but not much in the way of explanations. (I don’t think the Wikipedia page mentions them.) If I were to hazard a guess, though, I’d suspect they were a sundial.

Unlike Egypt and Sumer–and only somewhat like the IVC–we’ve uncovered no evidence of Norte Chicoan math or writing, and virtually no art. They did not make pots (no ceramics) so they had no pots to decorate (and their textiles have disintegrated greatly over the years.)

huanca stone
huanca stone

In front of the pyramids of Caral lie large, round, sunken pits–amphitheaters, from the looks of them. Unlike the Aztecs, however, archaeologists have so far uncovered no traces of sacrifice in the pyramids or amphitheaters–nor evidence of defensive walls or any sort of warfare. It could be that Norte Chico just didn’t have the population density to allow for warfare or the execution of captured enemies. However, since the whole excavation was only recently begun and archaeologists often seem to have a bias for proclaiming the civilization they’re studying peaceful until proven otherwise, I wouldn’t be surprised if this turns out to be incorrect.)

decorated flutes
click for the larger view, because the designs are actually quite good–from The Development of Flutes in the Americas

Archaeologists have found a bunch of flutes with engraved decorations, (proving the Norte Chicoans had both a musical tradition and a sense of humor,) and a few pieces of art have turned up, eg, a decorated gourd shell that archaeologists are claiming represents a local deity (the link is to one of the more questionable sites, so I am not 100% certain of its veracity–if someone finds this photo in an archaeological source, I’d be grateful to know about it.)

Archaeologists recently found three small statues, possibly offerings left at the Vichama site. One of the archaeologists claimed:


“…the position in which the statues were found as well as the larger size of the priestess, who has 28 fingers and toes and whose face is covered in red dots, demonstrate the importance women played in the pre-Hispanic cultures of Peru.”

Personally, I think archaeologists are over-confident when they make statements like this. How do we know she doesn’t have 28 fingers because the artist messed up, or that they aren’t toys?

Quipu in use
Quipu in use

Wikipedia also claims that they have found a quipu in the ruins. Quipus are sets of knotted strings used by the Inca empire (among others, probably,) to keep track of numerical matters like “number of soldiers captured in battle” or “bushels of corn owed in taxes.” Think of an abacus made of string; 5 knots on string one = 5 bushels of corn; 5 knots further down on the string = 50 bushels of corn, etc. Different colors of string could represent different items.

Interestingly, the Incas, 5,000 years after the Norte Chicoan society began, still did not have written language. I don’t know how you run an empire without written language, but they managed.

(There is some question of whether quipus could have been used to encode more complicated data, like language, but I have tried this and found the medium limiting. You can make a code in which phonemes correspond to a certain number of knots, [similar to codes where A=1, B=2, c=3, etc.] but this becomes unwieldy very quickly. I count 28 phonemes in the Incan language, [English has, IIRC, 40,] which means that just to encode a simple word like “quipu,” with four phonemes, [kh-i-p-u.] Just giving each phoneme a value based on its order in the chart, kh=15, i=2, p=7 [probably] and u=3, or 27 knots just to make one word.

Using different kinds of knots obviously improves the situation, but it still takes a fair amount of string to encode more than a few words. So while I find it reasonable that words like “corn” or “soldiers” might be spelled out in the knots, I doubt many people bothered to write down entire stories this way.)

Since 4,000 year old quipus look a lot like piles of disintegrated, tangled string, I’m holding off on declaring that the Norte Chicoans definitely had quipus until I at least find a picture of the thing.

(The Incas didn’t really use quipus for math, but they had some interesting abacus-like boxes.)

Some more pictures:

Caral, Peru
Caral, Peru


Caral, Peru
Caral, Peru








To be honest, while it’s a fine start for a people moving from hunter-gathering to agriculture, I’m not all that impressed. Maybe someday we’ll find out more about these people and discover they had something really interesting going on, but right now, they don’t seem all that distinct from a lot of other groups.




The Big 6 Civilizations (pt 2: Egypt)


2. Egypt

I know I don’t have to tell you about Egyptian civilization, but did you know the Egyptians had maths?

Problem number 56 from the Rhind Mathematics Papyrus (dated to around 1650 BC):

Egyptian seked
Seked of the Great Pyramid

If you construct a pyramid with base side 12 [cubits] and with a seked of 5 palms 1 finger; what is its altitude?[1]

Most Egyptian geometry questions appear to deal with more mundane matters, like the dimensions of rectangular fields and round granaries, rather than pyramids. (The Egyptians had not yet worked out an exact formula for the area of a circle, but used octagons to approximate it.)


Picture 4A “pefsu” problem involves a measure of the strength of the beer made from a heqat of grain, called a pefsu.

pefsu = (the number of  loaves of bread [or jugs of beer]) / (number of heqats of grain used to make them.)

For example, problem number 8 from the Moscow Mathematical Papyrus (most likely written between 1803 BC and 1649 BC, but based on an earlier manuscript thought to have been written around 1850 BC):

Example of calculating 100 loaves of bread of pefsu 20:
If someone says to you: “You have 100 loaves of bread of pefsu 20 to be exchanged for beer of pefsu 4, like 1/2 1/4 malt-date beer,”
First calculate the grain required for the 100 loaves of the bread of pefsu 20. The result is 5 heqat. Then reckon what you need for a des-jug of beer like the beer called 1/2 1/4 malt-date beer. The result is 1/2 of the heqat measure needed for des-jug of beer made from Upper-Egyptian grain.
Calculate 1/2 of 5 heqat, the result will be 212. Take this 212 four times.
The result is 10. Then you say to him:
Behold! The beer quantity is found to be correct.[1]

“Behold! The beer quantity is found to be correct,” is one of the most amusing answers to a math problem I’ve seen.

Picture 5The Egyptians also used fractions and solved algebraic equations that we would write as linear equations, eg, 3/2 * x + 4 = 10.

But their multiplication and division was really weird, probably as a side effect of not yet having invented a place value system.

A. Let’s suppose you wished to multiply 9 * 19.

B. First we want to turn 9 into powers of 2.

C. The powers of 2 = 1, 2, 4, 8, 16, 32, 64, etc.

D. The closest of these to 9 is 8, and 9-8=1, so we turn 9 into 8 and 1.

E. Now we’re going to make a table using 1, 8, and 19 (from line A), like so:

1        19
2        ?
4         ?
8         ?

F. We fill in our table by doubling 19 each time:

1        19
2        38
4         76
8         152

E. Since we turned 9 into 1 and 8 (step D), we add together the numbers in our table that correspond to 1 and 8: 19 + 152 = 171.

Or to put it more simply, using more familiar methods:

9 * 19 = (1 +8) * 19 = (19 * 1) +(19 * 8) = (19 * 1) + (19 * 2 * 2 * 2) = 171

Slab stela of Old Kingdom princess Neferetiabet (dated 2590–2565 BC), with number hieroglyphs
Slab stela of Old Kingdom princess Neferetiabet (dated 2590–2565 BC), with number hieroglyphs

Now let’s do 247 * 250:

The closest power of 2 (without going over) is 128. 247 -128 = 119. 119 – 64 = 55. 55 – 32 = 23. 23 – 16 = 7. 7 – 4 = 3. 3 – 2 = 1. Whew! So we’re going to need 128, 64, 32, 16, 4, 2, and 1, and 250.

Let’s arrange our table, with the important numbers in bold (in this case, it’s :

1       250
2        ?
4         ?
8         ?
16       ?
32       ?
64       ?
128      ?

So, doubling 250 each time, we get:

1       250
2       500
4       1000
8        2000
16     4000
32     8000
64     16,000
128    32,000

Adding together the bold numbers in the second column gets us 61,750–and I probably don’t need to tell you that plugging 247 * 250 into your calculator (or doing it longhand) also gives you 61,750.

The advantage of this system is that the Egyptians only had to memorize their 2s table. The disadvantages are pretty obvious.

Berlin Papyrus
Berlin Papyrus

See also the Lahun Mathematical Papyri, the Egyptian Mathematical Leather Roll, the Akhmim wooden tablets, the Reisner Papyrus, and finally the Papyrus Anastasi I, which is believed to be a fictional, satirical tale for teaching scribes–basically, a funny textbook, and the Berlin Papyrus 6619:

The Berlin Papyrus contains two problems, the first stated as “the area of a square of 100 is equal to that of two smaller squares. The side of one is ½ + ¼ the side of the other.”[6] The interest in the question may suggest some knowledge of the Pythagorean theorem, though the papyrus only shows a straightforward solution to a single second degree equation in one unknown. In modern terms, the simultaneous equations x2 + y2 = 100 and x = (3/4)y reduce to the single equation in y: ((3/4)y)2 + y2 = 100, giving the solution y = 8 and x = 6.

Megalithic Burials are so Weird

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.

Ancient Egyptian peacocks' tails
Ancient Egyptian peacocks’ tails

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.