Why was Stonehenge constructed with those woodwork joints (mortise and tenon; tongue in groove)?

Notice anything unusual about that upright?

Here is the first real post on this, my new Stonehenge/Silbury site – not counting the Hello World preliminary supplied by the WordPress host. It takes a close look at a detail regarding Stonehenge – one that is both at first sight practical and mundane,  yet baffling at the same time. I then use that detail to prise open what I believe to be the answer to the Stonehenge/Silbury enigmas – why were they built? Why go to so much trouble when, 5000 years later, archaeologists and historians are still asking what they were for?

Look first at the picture below.

It shows one of the upright sarsen stones which originally supported a lintel (the latter now next to it on the ground).  Notice the hump on top.

It is in fact the tenon of a mortise and tenon joint, the mortise being in the fallen lintel. Someone has handily provided a diagram to show the location of the two components of the joint – designed to locate one on the other to ‘tie’ the two together.

The two red circles show the position of the mortise (lower left) and tenon (top) respectively

But that’s not all. In addition to a mortise and tenon joint, the upright and lintel were interlocked by a second tongue in groove joint. Here’s a diagram showing this remarkable belt-and-braces arrangement, looking for all the world like something out of a woodwork class, yet laboriously fashioned using stone tools in the late Neolithic (pre-Bronze age).

Two mortise and tenon joints AND a tongue in groove (just to be on the safe side)…

The purpose of such joints is obvious where furniture is concerned. They allow a chair, table etc to support a weight without collapsing. But why the need to interlock the components of a heavy self-supporting structure like Stonehenge? Would not the force of gravity alone be sufficient to keep the arch-like trilithon arrangement of two uprights and a lintel crosspiece intact? Not even a hurricane could blow it down, surely?  Or even an infrequent earth tremor? What could possibly dislodge that mighty lintel, given that it is several metres high, towering above its builders, and weighing some tens of tons?

Answer? The doubly-secured lintel was to prevent it being detached by the ever-present  Enemy, who, arriving in large numbers, maybe at the dead of night, might come equipped with ropes, levers etc and attempt to dislodge those lintels, to send them crashing to the ground.

Why would the Enemy be so determined it its mission to destroy the crosspieces of Stonehenge?  Could it be that the circle of standing stones that we call Stonehenge came to represent a symbol of the awesome power of its builders over the nearby Enemy. Where the latter was concerned, did that circle of stones, looking somewhat sinister even to modern eyes,  represent something else – like summary execution, and a humiliating and highly visible fate to follow – one in which those lintel crosspieces played a key role?

So who was the Enemy? And why was Stonehenge a prime target for raiding parties, and accordingly designed to resist being torn down? Those questions will be the subject of my next posting

Further reading on those mortise and tenon joints

 Update April 22, 2016 (4 years on!)

I think I’ve sussed it out. Shame that all my text (imprudently composed online) disappeared when I hit the Publish button! Just as well that a picture is worth a 1000 words. Here’s the schematic I made to accompany the posting:

new trilithon 1 aligned plus mound penultimate for blog

See the new posting for a longer-than-usual caption to the above, essentially a Band-Aid operation. I’ll try restoring the full posting in easy stages, though that may take a few days.


Update: Jan 28 2018 (!)  Have just received a new comment (approved), but it’s not displaying correctly as yet under ‘Recent Comments’. Hopefully the problem will sort itself soon.

Here, belt and braces, is the comment from Raymond Nicolle:


I am biased because, in 1967, I personally saw a “flying saucer” in broad daylight come out of a cloud formation, turn, bank, and fly straight up in the air and disappear. So that makes me biased. I find it hard to believe that my ancestors, dressed in skins and with deer horns and stone clubs, created the carved stone parts of Stonehenge. The creation of mortise and tenons alone out of stone harder than granite boggle the mind let alone tongue and groove construction. My ancestors were too busy finding food, procreating and fighting off neighbours…in other words, just surviving. To my mind, the constructors of the granite and dolomite parts of Stonehenge were visitors to Earth who wanted to leave proof of their visitation. They wanted the construction to last for centuries and stand as a signal to any other visitors that “they were here”. They did what I would have done…leave a huge natural edifice and carry on exploring the universe.



Addendum: March 16, 2018

Have decided to add the following image as an addendum to ALL my Stonehenge postings (some 24 in all, here and on my sciencebuzz site). Why not – since it’s my considered answer to the ‘mystery’ of the monument’s peculiar architecture, the conclusion to some 6 years of  deliberation?



I say Stonehenge was designed as a giant bird perch, a ceremonial monument dedicated to ‘sky burial’, i.e. soul release from mortal remains to the heavens via AFS (avian-facilitated skeletonization, considered the height of fashion (and practicality) in Neolithic-era 2500BC! The stripped remains were then cremated, so an apt description of Stonehenge might, as previously suggested, be PRE-CREMATORIUM.



About Colin Berry

Retired science bod, previous research interests: phototherapy of neonatal jaundice, membrane influences on microsomal UDP-glucuronyltransferase, defective bilirubin and xenobiotic conjugation and hepatic excretion, dietary fibre and resistant starch.
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14 Responses to Why was Stonehenge constructed with those woodwork joints (mortise and tenon; tongue in groove)?

  1. Colin Berry says:

    Thanks Ray

    Your comments convey an appreciation of the enormity of what our ancestors achieved at Stonehenge (especially) and rightly focus on what might be described as Neolithic -era technological precociousness.

    But it’s my gut feeling, aided by a little additional research, that our archaeologists are failing to get their heads around the nature of rapid human progress in the Neolithic period, driven by practical considerations, like how best to dispose of the dead. What may have seemed practical and proper in one century may not have seemed so in the next (but we lack a continuous archaeological record by which to track all those incremental changes in fashion).

    On thing’s for certain: the mind-boggling structure we call Stonehenge did not appear in the blink of an eye, so one should not be too quick to rule out anything that required centuries of organized human labour and ingenuity, each stage improving on the one before.

    I believe Stonehenge evolved in stages over the course of many centuries, indeed millennia. Being a longstanding site for disposal of human remains, recognized as such for hundreds of miles around, it gradually became smarter and smarter as to how to fulfill its role quickly and efficiently, leaving nothing at the end except a package of cremated bones for grieving relatives to do with as they wished.

    Stonehenge ought by rights to be seen as a monument to an early focus on the part of our island ancestors towards practical and efficient solutions to everyday problems, notably funeral arrangements. Think of it as an early version of Cape Canaveral and its moonshots (except it wasn’t rockets that were being launched into the skies and outer space).

    If that required what I have termed AFS (avian-facilitated skeletonization, aka sky burial) as first step, followed by end stage cremation of the pecked-clean bone that remained, then I’m inclined to say “so what?”.

    In what way is AFS, discreetly screened from public view by those heaped-up henge banks, any more cringe-making than than speculating on what happens to our own modern-day elderly relatives who at the end of their days are either buried deep in the ground or sent off to a crematorium? There are no easy entirely tasteful, aesthetic answers surely when it comes to disposal of the dear departed.

    Thank you for the appreciative comment re this blog (and the difficult task it is trying to achieve, namely to get folks to think realistically about Stonehenge and its true purpose, requiring unsophisticated Neolithic technology for disposal of the dead!).

    I say Stonehenge was essentially a crematorium (with an initial pre-skeletonization stage involving voracious gulls and other feathered ‘friends’ seeking a high-protein meal that no one these days wants to think about).

    The trick was to attract a regular clientele of hungry birdlife, gulls especially, progressing chronologically over the centuries though cliff-like henges, then timber posts, then standing stones… Think of Stonehenge as a giant bird-table (with a nearby add-on crematorium that was not willing to accept whole bodies!).

    I hope I haven’t bored you. It’s always a pleasure to receive comments from someone with an enquiring mind, willing to lend an ear to new thinking…

    • Colin Berry says:

      PS: I’m no expert where shaping stones of differing hardness is concerned. Having said that, it’s worth remembering that the mortise and tenon joints were not in the igneous blue stones but the local sarsen megaliths – sedimentary sandstone – used for the main outer circle. Granted it’s not the soft crumbly variety of sandstone: sarsen stone is highly silicified, giving it a high rating of 7 on the Mohs scale of hardness, allegedly almost as difficult to shape as an igneous stone.

      But here’s a possible factor that needs to be taken into consideration: sarsen stone is said to pick up lots of water, being somewhat porous (it was abandoned early on as a building material, making homes damp and uninhabitable). One can’t help but wonder if it’s maybe easier to shape sarsen stone when its pores are saturated with water, say after heavy rainfall. Maybe frost getting into waterlogged pores makes it weaker still. Was that the trick for creating those tenons one wonders, which as you rightly point out are/were something of a technological wonder in their own right. Maybe those Neolithic M&T makers had to play a waiting game…

      PPS: from wiki entry on sarsen stone:
      “Sarsen is not an ideal building material, however. William Stukeley wrote that sarsen is “always moist and dewy in winter which proves damp and unwholesome, and rots the furniture”.

      So maybe the problem is not excessive porosity, but lack of it! Maybe condensation forms on the surface of the stone like it does on car roofs at night, being unable to soak away. That weakens my argument for water-assisted weakening of the sarsens… 😦

      • Stanley Marshall says:

        Interesting point about the Rosetta Stone. Could thousands of hands tracing the “ carved” letters over hundreds of years have resulted in removing the rough edges? I also believe the face side of the stone was covered in wax at one time to prevent such further action. The answer might never be found and that is the interesting part of these discussions Sam

        Sent from my iPad


  2. Raymond Nicolle says:

    I am biased because, in 1967, I personally saw a “flying saucer” in broad daylight come out of a cloud formation, turn, bank, and fly straight up in the air and disappear. So that makes me biased. I find it hard to believe that my ancestors, dressed in skins and with deer horns and stone clubs, created the carved stone parts of Stonehenge. The creation of mortise and tenons alone out of stone harder than granite boggle the mind let alone tongue and groove construction. My ancestors were too busy finding food, procreating and fighting off neighbours…in other words, just surviving. To my mind, the constructors of the granite and dolomite parts of Stonehenge were visitors to Earth who wanted to leave proof of their visitation. They wanted the construction to last for centuries and stand as a signal to any other visitors that “they were here”. They did what I would have done…leave a huge natural edifice and carry on exploring the universe.

    • Colin Berry says:

      Yes, but Stonehenge didn’t start as stone anything.


      It began a circular bank and surrounding ditch, i.e. a henge. Later it acquired a large collection of timber posts. Only then did megaliths arrive (smaller bluestones, 5 or 6 feet high, ) followed later by the much taller sarsens.

      Why would little (or large!) green men go to all this trouble over centuries, nay millennia?

      Sure, the stone is hard, especially the igneous dolerite and rhyolites of bluestone. By the same token, one piece of dolerite can be used to chip away at another. The ‘chipping’ techniques had, after all, been perfected in the Stone Age, preceding the Neolithic (New Stone) age by many millennia.

      • Ray Nicolle says:

        To my mind, it is one thing to chip away at arrowheads or spear points and entirely something else to chip away at a massive, igneous-hardened, stone block to make a tenon. A tenon!? I guess you have visualized the huge amount of stone you have to chip away just to make a rock tenon to fit into a mortice hole. I can imagine pounding out a mortice hole with a bluestone boulder but a tenon? But when I try to imagine my crude ancestors who inhabited the Isles at that time, planning and creating mortice and tenons out of those blue stones, I admit I have to supress a giggle. Then joining them with tongue and groove and also shaping them esthetically… it beggars my belief. I wish I had the same faith in my ancestors as you have.

        As to why, whoever created these marvels, came back time and again and added to them…I have no idea. Maybe we became a tourist destination?

        As an aside, have you seen that magnificent Egyptian lion statue carved out of red granite? When I saw it, the first thing that came to my mind was the massive amount of red granite that would have to be chipped away just to create the basic outline of a lion from a big chunk of granite let alone the finished product. Chipped away from igneous hardened rock with crude tools? I wish I could believe that. I really do. But, to me, it looked carved and polished. Why wouldn’t they use more malleable sandstone like the Romans? Have you read any studies that try to show the difference between statues that have been chipped and more modern statues that have been carved using modern technologies? Also, when I got to look at the Rosetta Stone, it looked like it had been typed…not scoured and etched with sticks and sand. But that’s just me.

        Thanks for your blog. At my old age, I’m trying my best to keep my curiosity alive and your blog is super that way.

  3. Colin Berry says:

    Copper Age? Bronze Age? Iron Age? Even as long ago as 2000-5000 years ago, our ancestors were amazingly sophisticated in the technical spheres that aided their everyday life. Think of the sophistication of blending metal from two entirely different ores – copper and tin – to make bronze. Think of the temperatures needed to get iron from iron ore!

    I’m not sure if you’re aware of my entire thinking re Stonehenge which evolved over some 4 years after this 2012 posting. Most of it was posted to my sciencebuzz site, and only briefly summarized in the final 2016 posting on this site:


    I could give you a 100 word summary if you want, but if you’re like most folk – archaeological establishment included – you’ll take one look, shrug your shoulders and walk away (thanks to the emphasis placed on the Neolithic hangup re the need to liberate the soul of the newly dead to the heavens from its earthly prison – and how southern England’s chalky uplands+ gouged-out gull-attracting henges were the initial steps in an evolving strategy based around AFS (avian-facilitated excarnation). Seahenge and Stonehenge were simply add-on furniture needed to complete the safe-from-predator design that enabled English gulls to safely perform the task performed by vultures on the Continent better evolved and equipped for a quick scavenging role.

    Yes, it was worth all the effort, lugging those monoliths vast distances, because gulls etc had already colonized the wide open chalk uplands of Wiltshire, ceasing to be entirely coastal-based. The aim was to keep them there, with regular timed flesh-based offerings, to train and encourage them to take on the role of English “vultures”, ensuring recently dead relatives an assured and closely-managed send-off to the skies!

    Carved-out-of-countryside gull-attracting henges – a Brit speciality made to resemble white coastal cliffs while far inland – was Mark 1 technology. Stonehenge with its elevated bird perches, was just a highly centralized Mark 2 development – a carefully-contrived safe haven pseudo-cliff face for opportunist free-range gulls in search of regular and assured free lunches (plural note!)!

    I strongly suspect, btw, that 3000 years ago, Stonehenge was completely chalked-over to make it a gleaming white! Centuries of rain and its dissolved carbonic acid have chemically dissolved the chalk, leaving bare rock that gives no clue as to original super-henge-like purpose!

    • Stanley says:

      Seagull perches?.
      I must confess that I have never heard this phrase in connection with anything built by man, Neolithic or modern.
      My first visit to Stonehenge was in 1950, when my parents took me by chara to see the henge.
      My next visit was in 1953, when my school Northrrn Polytechnic, took 24 of us (plumbers, brickies, painters and carpenters)
      To see the henge and to dinscuss how it was constructed, you will note that I have called us by trade, The Poly was a building school were we studied building trades along with our GCE as they were called then..
      I am very familiar with how metals are mined, and formed into usable building products, like lead, copper, tin, aluminium, zinc, cast iron ,wrought iron etc.
      I know how to bend shape and dress all these metals.
      On leaving school I completed a five year apprenticeship in the ” building trade”, During which time I handled every product ct that was made to erect or demolish a building.
      Two years National Services as a sapper building bridges, floating rafts and then how to blow them up.also made me aware of what modern men could build and why.
      As a draughtsman, engineer, and Q S , and cost engineer I completed over 60 years in the construction industry., working on some of the most sophisticated and unmentionable building projects, with the finest Architects, Engineers and builders.
      I know how inventive, cleaver and industries Neolithic peoples were and that modern buildings are built on the foundations ( not actually) of the past builders.
      But I have never heard of your theory about seagull perches, so yes I would be obliged if you could recommend any book etc which discusses this theory.
      Oh! I don’t shrug my shoulders either as I have said I have worked on what at the time was inconceivable. Funding for research not easy to obtain.Other wise every crack pot would be applying.
      So F you could recommend some reading I would be obliged and good fortune in whatever project you are worked no on.
      Regards Sam

      • Colin Berry says:

        This has to be a quickie holding reply, Sam, since I’ll be out of the house, away from the laptop for the next few hours.

        There’s a scant literature linking Stonehenge with excarnation/sky burial. The first is the BBC feature on Seahenge in 1999, which caught my attention, flagging up as it did the link between a small-scale timber version of Stonehenge and excarnation by birds (though seagulls were not specifically mentioned).

        1. Seahenge gives up its secrets, 1999
        Stonehenge was curiously not mentioned, except for this single intriguing reference:

        “Norfolk County Council’s Archaeological Unit identified the find as a Bronze Age timber circle dating from around 2000 BC – roughly contemporary with Stonehenge. Inevitably, the circle was dubbed Seahenge.”

        The BBC then promptly dropped all reference in its later updates to Seahenge!. That’s thanks I suspect to being carefully led off the scent by local archaeologists looking to promote less gruesome explanations for the novelty that was right on their doorstep, previous marshland, uncovered by winter storms, now partly re-assembled in their visitor-attracting local museum collections:

        2. The second is the more recent article by retired funeral specialist Ken West in 2014, with whom I’ve been in email contact.

        Ken West 2014
        “Stonehenge and sky burial”

        He mentions birds, listing several, though gulls again are not specifically mentioned (and he’s cool on my gulls idea as well!).

        Ken’s now turned his hand to novel writing and no longer writes about ‘sky burial” as far as I’m aware, so thanks first to official indifference, probably hostility too, to say nothing of media management and now my losing an ally in the new ideas department, the proposed link between Stonehenge and excarnation has simply failed to take off.

        So thanks for your interest and for providing an opportunity to flag it up, after my having given up flogging what seemed like a dead horse some 18 months ago, returning to my other main interest – that Shroud of Turin!


        I’ll be interested Sam in hearing your own mature thinking and views where the seagull idea is concerned – and/or ones of your own. Do keep in touch. Better still, visit some other Stonehenge-featuring sites and include a link back to this one!

  4. Sam says:

    Perhaps the builders were saying look how clever we are. Didn’t Sir Christopher Wren design some columns just short of their purpose to prove that he new better than the non builders?
    Wonderful masons. The mystery to me is how they got the stones to Salisbury at all?

    • Colin Berry says:

      If Stonehenge had been intended as a show-off monument (“look how smart we are compared with you lot!”) there would surely have been a series of Stonehenges, each trying to outdo the others in terms of size and grandeur. But there’s only one Stonehenge with those distinctive crosspieces that I know of (or as I call them, bird perches).

      But there’s also the modest Seahenge on the Norfolk coast, humble timber, not stone construction. It’s hard to see what bragging rights it would have acquired. So it makes more sense to look for a common purpose shared by the two henges.

      And there is indeed a common purpose that can be inferred. Both existed for ritualized excarnation – defleshing of corpses, as an alternative to bodies being buried in the ground to rot or cremated whole. “Sky burial” in other words. Let birds with their beaks do an initial clean up – no flies, no smells, no maggots. Cremate what’s left (thus the deposits of cremated bones at Stonehenge and elsewhere).

      The archaeological establishment does not wish to hear about Bronze and Iron Age Brit-style excarnation. Why not? They know the subject is a turn-off – hardly guaranteed to keep the project grant money for new digs etc rolling in – much better to waffle on endlessly about pagan ritual, symbolism, astronomical alignments bla bla…

      Me? I prefer reality, even when it’s harsh reality…

      • Stanley says:

        So there is only one example of a ” stonehenge ” with the characteristics of (carpentry joints)?
        But there is a Seahenge constructed from timber at this time..
        Why only one Stonehenge and bragging rights?
        Perhaps the people who constructed ” Stonehenge ” had reached the pinnacle of their stone building technowledgy ? We are talking of a population of approximately 100,000 people in the whole of GB. So let’us assume that 1/3 occupied Southern Great Britain .
        33,000 occupied the area surrounding say ” Wiltshire ” ( poor analogy by me here), but t I think you know where this is going?
        What percentage of these 33000 people would have the knowledge to construct Stone henge ? Presuming that they all lived local to the site oif construction, which would be shall we say far fetched?
        Life expectancy of a male at that time? 40 years? +/- 5 years. .
        Not a lot of time to devise new techniques or pass on new knowledge or devise new building
        methods, from very few people to conceive of the idea to dump the dead for excarvatnation?
        it would not be unreasonable to conclude that the very small percentage of a still further small percentage had little time to know how to build an henge at all let alone consider the disposal of dead bodies.
        With such a small sample of humans is it not possible thar they simply did no know what more they could do and thereby ” run out of iideas so this was the best they could do?” ” Look at us we built this”
        Hence there is only one stone heng constructed with mortise and tenon joints?Not sure about your other assertions I am looking at the construction, skill, logistics and time it took to build Stonehenge?
        A truly remarkable achievement.
        Regards Sam


  5. Ben says:

    Have you been to Peru or other megalithic sites? They often use similar stone tricks https://upload.wikimedia.org/wikipedia/commons/8/86/Peru_Sillustani_Grave_Tower_Chullpa.jpg (although terrible reconstruction/restoration job attempt)

    Interestingly enough, these towers all collapsed on the same sides and rocks are strewn far from the towers themselves (they are heavy). Requires explosive forces to do that kind of damage. Strategically placed Dynamite? Strategically placed thunder strikes? Comet breakdown/strike (in the region) causing a deluge or air pressure wave?… http://m.phys.org/news/2014-08-year-old-nanodiamonds-multiple-continents.html

    …and the last thing they are, are tombs (at least for their original designed purpose).

  6. Pingback: Mortise and Tenon (Week 3) | A Year at College of the Redwoods Fine Woodworking

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