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Secrets of Lost Empires
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Live Event
Question: I've heard that there are stone walls on Easter Island that look very much like the Inca stone walls. Have you seen them, and do you know if there is any evidence on Easter Island about how they might have been built?

Answer: Yes I have seen several walls here...there are many walls on Easter Island. I haven't seen them all but I have seen two that are particularly similar to Inca walls. I think they were probably built the same way the Inca walls were built. The real question is do they suggest that the Incas somehow made a voyage to Easter Island to build them? I think that the answer to that is probably not. It's the sort of question you can never answer 100 percent in the negative. In other words, we can't prove that something didn't happen but to date a lot of excavation and study has been done on Easter Island. Absolutely no evidence has been found of visitation by Andean peoples such as broken pottery or stone implements or really anything else that would indicate the presence of Andean people here so I think it's very unlikely that these walls were built by Andean peoples or that they were influenced by Andean builders. But they are remarkably similar to some of the walls of Peru, especially these two examples, so I think that will forever remain somewhat of a question. I believe that the prevailing answer to date, which is that the Peruvians had nothing to do with them, is probably correct.

Question: In your recent program you had two options for the Inca's ability to create their magnificent stone walls. I believe that the Incas might have had a different approach. Instead of working vertically between two stones with the second being supported precariously above the first, they could have worked horizontally by placing the stones on their sides and working on two or three joints with three or four stones at one. They could have used the compass to transcribe one stone's features to the next. Then when both joints are finished, they would set the first stone of the wall. With the joint between the second and third stone already complete, they would start on shaping the fourth stone to a side of third stone, and so on until completion. This method would have the advantages of only moving the stones which could be enormous, once, without the danger of perching a several ton stone above a skilled stonemason. ~Brian

Answer: This is a good question. You obviously understood from our "Nova" program that the easiest joint to fit between two large stones is the one that places them both next to one another, sitting on the ground. I believe this is how the stones at the bottom of the walls were fitted, but the only way to use this method for the joints above that would be to pre-fit them on the ground with the stones laying on their backs, and then reassemble them in an upright position. There are two reasons why I believe that this was not done, although I do think it would have been a good idea. Some sites were abandoned under construction. Sacsahuaman was one such site. There are many indications the project was not complete when the Incas stopped working on it. If that were the case, we would expect to find evidence of blocks lying on their backs being cut to fit prior to their assembly on the wall. We find no evidence of that at Sacsahuaman or anyplace else. The other indication that we would expect to see is that the upper course of the wall would be finished. The impression of the stone that is not yet placed on top would already exist because by definitions the stones would have benefited previously lying on their backs out in front of the wall, but what we find is that the upper course is actually rough, natural shapes. The upper layer of stones was never cut, indicating that the final course was to be fitted in place rather than on the ground out in front of the wall.

Question: One person tried using mirrors to heat the rock to chip away pieces of the rock without any success. I think his idea would probably have worked if he would have used something like a crystal, which should be native to the region, to pinpoint the heat of the mirrors on to the rock. ~Alan

Answer: You're referring to Ivan's method of using mirrors and concentrated solar energy to shape the rocks rather than stone hammers. I really don't know. It's possible that crystals would concentrate solar energy better than the mirrors that were proposed by Ivan, but we do not believe and cannot find any evidence that the stones were melted in order to cut them to their final shapes. Instead what we find is universal evidence of shaping with stone hammers, and for this reason we do not believe that any method, whether crystals or mirrors which melted the rocks, was used to shape them.

Question: When they built the grass bridge, how did they send the rope from one side of the gorge to the other? ~Julia

Answer: This was not my segment of the show, but I am familiar with it. They tied a small-diameter rope onto a swimmer who swam across the gorge. Using that small-diameter rope, they were able to pull a larger-diameter rope across, to which they could then attach the very heavy static lines for the bridge. That does raise the question of whether this could have been done with the river in flood. They actually did this experiment with the river at fairly low water so that swimming across it was not a difficult thing to do. I think the answer is that it would have been very difficult to accomplish that with the river in flood at high water. Not all the bridges were as long as the one that "Nova" built, and in some cases a small-diameter rope could have been thrown across from one side of the gorge to the other, therefore eliminating the need to swim, but for a long bridge like the one we built for the "Nova" show, I think they really had to do it at low water when a swimmer could safely make it across.

Question: Could it be that the Incas used friction between massive blocks and actually ground them together to get the perfect fit, possibly laid one block on its side on the ground and somehow rotated the other one on its side on top of it until it was a perfectly flat surface, then take the next block that will mate up with it and grind it down in the same way? I have seen them and it is incredible how they did it. ~Wayne

Answer: There are several reasons why I believe that the method proposed here was not used by the Incas. For one thing, where stones have been removed from the lower courses beneath them, we see the imprint of the upper stone in the tops of the lower ones and the imprint is often of a very strange warped shape. That is to say that it is not a shape that would have been created by rotating or moving the upper block on top of the lower one. Also, the method proposed would be very difficult to use on the vertical surfaces which are generally fit, in fact, just as tightly as the horizontal surfaces.

Question: Vince, how did you first become interested in Inca civilization? ~Jen

Answer: I was a mountain-climbing guide for many years and on a trip in 1982 I took some friends and climbing clients to the Peruvian Andes. On the way into the mountain-climbing area, we went past a number of wonderful Inca ruin sites, and I was so excited that when I returned home, I decided to read about them and find out about their history. I was shocked to find that there was very little, if anything, to read about them. No one had bothered to make maps of them or study them in any detail. So I decided to go back the next year and make maps of them myself, and the rest is history because I got fascinated with the entire process and have been back to Peru at least once a year since then, some years even twice.

Question: How many suspension bridges are there in the present day Inca empire? ~Connor

Answer: I'm not entirely sure what the numerical answer to this is, but it is a very small number, probably fewer than ten. There are many sites, however, where the stone abutments which once held Inca bridges remain in place. I would say those sites probably number up to 100.

Question: I think the stonemasons used mud casts to generate a perfect fit between the large stones. First they smoothed the stones as much as possible by hand. They then made a mud cast of one stone face. They had to let it dry. Then they used it to grind the other stone into shape until it made a good fit. ~David

Answer: This approach has been suggested by a number of researchers, and with very small or moderate-sized stones could possibly have been used. We have no evidence that it was or was not, and so it's a difficult question to answer, but for very large stones, such as those we see at Sacsahuaman, the molds in order to shape the faces of those stones would be almost as big as the stones them self, especially when one assumes they would have to be reinforced so as to hold together for their use in construction. We do not believe that this method was used.

Question: What did the Incas have to secure the stonework into the mountains? ~Michael

Answer: Many of the walls that you see built by the Incas were retaining walls up against a slope behind. And they are still after 500 years of unattended use in good condition generally. This tells you that they were very, very well built and that the conditions of the ground behind the wall was very carefully planned. This means that drainage was provided for so that the earth behind the wall could not become saturated, heavy, and push the wall down, and it also means that probably the stone walls are very much wider at their base into the mountain than they are at the top where you see them on the surface.

Question: How long will the grass bridge that was built last? ~Travis

Answer: The village where the bridge was built rebuilds the bridge each year, and we are told by the residents of the village nearby that if they did not rebuild it every year, after about two or three years it would become unserviceable. So I would assume that perhaps two years would be the actual life span of a grass bridge.

Question: Vince, how did you first become interested in Inca civilization?

Answer: In 1982 I was a mountain guide and I took some clients for a climbing trip in the Peruvian Andes. On the way into the mountain-climbing area we went past a number of wonderful Inca ruin sites and I became so excited that when I returned home, I decided to read about them and find out about their history. I was shocked to find that there was very little, if anything, to read. No one had bothered to make good maps of them or study them in any detail. So I decided to go back the next year and make maps of them myself. The rest is history, because I had been going back every year and sometimes twice a year ever since.

Question: I have noticed that between work they ate guinea pigs and potatoes. What other staple foods did they have? ~Rosemary

Answer: The traditional food of the Andean Indies up high are potatoes and yuca, which is sometimes called ma'amock in the lower country of the Amazon basin. Other plants that are very important to the economy are corn, which is called the Spanish word "maize," and other vegetables. The only staple source of meat to the early Andean Indians prior to the arrival of the Europeans was the guinea pig, which they grew in their homes, and then wild game meat of various kinds which grew in the countryside. Today there is relatively little wild game meat left and so sheep, pigs, cows and so forth have taken the place of the wild game, but the guinea pig is still a very important staple in the diet of a high country Indians.

Question: I'm interested in the record-keeping in woven strands. Was there any archeological evidence to support this method? ~Martha

Answer: There is very clear evidence in the form of about 400 surviving quipus. The device I believe you're refer to is the quipu. About 400 of them exist in museums around the world. And it was, as the questioner suggests, a very clever device made of knotted, colored strings which was clearly used to record information largely in a numerical form. We do not know what information was recorded but we have deciphered the method in which the knots indicate numbers so that scientists can read the numerical values and we know from the various surviving quipus they were used to add and subtract and multiply and divide. What we do not know is the degree to which abstract information, like historical information and other such non-numerical data could be stored on a quipu. Many researchers think the quipu was used like the rosary beads in a religious context or used to enforce the memory of traditional legends and histories, and several of the Spanish chroniclers report this to have been the case. But we really have no way to confirm that at present.

Question: The show didn't mention the political system the Incas used to rule that large an area. I have done some reading on this and find it fascinating. Have you done research on the Inca political system? ~Penny

Answer: The Inca political system is not particularly close to my specialty of research, but the Spanish chroniclers are fairly clear on the system used by the Incas to manage their empire. The sapa Inca himself was the supreme leader of the entire system. He was somewhat similar to the pharaoh in ancient Egypt in that he was both a political leader and believed to have divine power. Beneath him was a very large bureaucracy of officials who managed every aspect of life in the early Andes and managed it very efficiently according to the Spanish chroniclers.

Question: How does the shaping of the massive blocks compare with other ancient structures like those of the Egyptians', the Greeks', Romans', et cetera, tools used? ~Karl

Answer: The megalithic stonework of the Incas is in, at least its finest experiences, somewhat unique in the world. There are, as it turns out, other places where a similar approach was taken, but not very many. Most of the stonework of the old world was done similar to the way stonework today is done. That is to say the stones were squared off and fitted together in a predictable manner. Very early Egyptian stonework is somewhat similar to Inca stonework and actually at the moment I happen to be on Easter Island, where we have found stonework which is very similar to Inca stonework. The difference is the stonework of the Incas and these other unusual builders was not squared off. In fact, the one thing you will never find in an Inca stone wall is a square corner, a straight line or a flat plain, unless it is by accident. The result is that every single stone in the wall fits in only one place. The wall cannot be prefabricated. It must be erected one stone at a time with each stone very carefully fitted into its own particular location.

Question: What type of rocks were the Incas using? Is there a difference between the wall rock and the rock used for forming the angles? ~Robert

Answer: The Andes, of course, are a very complicated mountain range and many, many forms of rock exist there. The Incas chose the ones that they found in the area in which they were building and tried to use the best material that they could for construction. The result is that many monuments are built out of different stone. For example, the stonework at Machu Picchu is largely white granite; the stonework in Cuzco is often dark andesite; the stonework at Sacsahuaman in the hills above Cuzco is generally blue limestone. The stonework at Ollantaytambo, a large ruin not far from Cuzco is rhyolite. In all cases the shaping of the stone had to be done by using an even harder material. Generally speaking, what we have found is balls of dolorite, which is a very brittle... hard, not brittle, but hard material with which the softer stones could be pounded into shape.

Question: Had the Inca walls been x-rayed or examined otherwise behind the exposed face? Perhaps it's only the front face of the stones which fit together so well. Though still challenging, it would reduce the apparent difficulty a bit, a pretense hiding reality. That would make the Incas the first advertising agency. ~Robert

Answer: I'm unaware of any technical treatment such as x-raying that might have been used for this purpose, but it is actually unnecessary since we have many places where the original walls have fallen and we can read the cross-section of the original construction in the area that has fallen out of the wall. And the answer is that in some cases exactly what the questioner suggests is true, especially the vertical joints are often fitted only at their outer face and not very well fitted back into the depth of the wall. In almost every case, however, the bedding face, that is to say the horizontal face on which the rock bears, is well-fitted throughout its entire width.

Question: Did you give any thought to the way the Incas originally carried the stone before bringing it to the building site? If they were able to break up a very large stone into building block size and keep a record of the original sequence of breakage and then reconstitute that order at the building site they could save a great deal of work in reshaping, since the blocks they were putting together had originally fit together in the first place, and a minimum of polishing would be required. ~Barry

Answer: This is an intriguing idea which has occurred to a number of us researching this question. However, in almost every case we know of, the quarries of the Incas were simply large boulder fields where loose rock had fallen from mountain faces and were chosen for their quality and their shape, rough shape and then dragged down to the building site for finishing. There is one exception to this that I'm aware of, and it is at the site of Sillustani, near the shores of Lake Titicaca in Peru where a stone is actually being chopped out of live rock in the same manner in which the Egyptians, for example, quarried their rocks. So the Incas were apparently aware of and used this method but it is very, very rare.

Question: At the height of the Inca empire, what was the population? ~Elmo

Answer: We really don't know, of course, and the Spanish chronicles are not very clear on this question. But various researchers have come up with estimates based on various early records and those estimates range from perhaps six million to as many as 20 million. But the answer really is unknown.

Question: Didn't they drill holes in the rocks, pour in water, let winter come to freeze the water, which expands the water, thus cracking the rock? ~Gene Kopelson

Answer: We have not found evidence of this, although some of the stones in some of the quarries show lines of relatively shallow pits dug in a linear pattern. It is possible that these were intended to receive wooden wedges, which were then wet and when the wood swelled under the wetting. The idea was to crack the rock open. This is a method that has been used elsewhere in the world and was used in Peru in colonial times. We really aren't sure whether the rocks we see in the quarries that show this pattern date from the Inca period or perhaps from the period shortly after the arrival of the Spanish conquistadores.

Question: Do the blocks need to fit perfectly throughout or just along the edge? Is there any evidence that they were less careful nearer to the center of the blocks? ~Leon

Answer: This is similar to an earlier question, and the answer is that in many cases the rocks are perfectly fitted throughout their entire depth across both their horizontal bedding faces and their vertical rising faces. But in some instances we find what the questioner suggests, that only the horizontal bedding face is fitted perfectly for the future depth of the rock and the vertical rising face is fitted perfectly only at the visible edge, and behind that the rocks simply taper away from one another and loose fill is placed there to stabilize the rock in its position.

Question: It appears that the modern civilized world is no match against the Inca's ability to motivate a large labor force. The effectiveness is awesome. What do you think enabled this incredible phenomenon? ~G. Michael

Answer: It is clear that the Incas and for that matter other pre-industrial societies were very excellent at managing large labor forces. And it is known that in the case of the Incas a large labor force was available in the form of taxation. The people that were in the Inca empire under the rule of the Incas did not pay taxes in the way we do in the form of money. Instead they paid in the form of their time. And at some period of the year when they were not needed in their villages for agricultural or other work important to daily life, they were called into service of the state, and many of these people were put on construction projects. We don't know how many of them there were, but the monuments speak for themselves. It clearly involved very large numbers of people, and these people must have been managed very efficiently in order to accomplish what was done in the relatively short time the Inca empire was at its peak. This time lasted roughly from the mid 1400's until the arrival of the Spaniards in 1532, which, when one thinks about it, is not a very long period of time to accomplish the building program that we see scattered around the Andes today.

Question: Why was no information about the methods used for the construction of the walls passed on to the descendants of the builders? ~Nancy

Answer: We have no idea, but the questioner is absolutely right, almost no such information is known to exist. It may be that the processes were so common and so well known among the people at that time it never occurred to them that there was any point in making a record of them. Also, of course, in the case of the Incas, who had no written language, it is unclear what form that record would have taken. We do have, as an earlier questioner suggested, quipus, which are knotted strings on which records were kept, but we have no idea what information was recorded there since all we can do is read numerical values of the knots but cannot read what those numerical values signify.

Question: What types of weapon artifacts have you uncovered? Atlatal, bow and arrow, bola? Also what tools are evident? ~John

Answer: In my own work I do no excavations and therefore I have uncovered nothing of the kind suggested by the questioner. However, other researchers, of course, have. I believe that the Inca period was long after the use of the atlatal ceased in the Andes, if it ever was used there. The weapons we know to have been popular to the Andes are bolas for catching animals; we know the Bow and arrow was used by their allied tribes in the Amazonian basin. We did not know whether the Incas themselves favored the bow and arrow, but we suspect they did not. Their favorite weapon was the sling.

And they were reportedly excellent marksmen with the sling.

The advantage of the sling over the bow and arrow in the Andes is that ammunition is plentiful for the sling and almost non-existent for bow and arrows. But we really don't know.

The other weapon that was very widely prized by the Incas was the hand-held club, and a great many different varieties of clubs and mace heads have been found in excavations. So that suggests that Inca warfare at a distance was largely conducted by the throwing of stones with slings and by possibly the use of javelins and spears and at close quarters by the use of clubs and maces.

Question: What was the dress of the ancient Incans made of and was it colorful? It is pretty cold up there in the mountains, isn't it? ~Joshua

Answer: Yes, it is quite cold up in the mountains, and the clothing made by the Incas was largely made out of the wool of llamas and alpacas, the New World version of the camels, and are still widely used by the Indians of the high Andes. In the lower country, where such quite warm garments were not needed, cotton was used. In the coastal deserts, for example, it is thought that most of the garments were made from cotton. In all cases, they were very colorful and we have many examples of Andean weavings, some of which are thought to be among the finest weavings ever made in the world.

Question: Just as the bridge was built with a group of people living near the river, is it probable that the Incas could have gathered large groups of people to work on the stones? Is it possible to have had large groups of people working on the stones at one time in order to build the temple and other buildings? ~Chuck

Answer: It is known that the bridges were largely built by nearby villagers. However, in the case of the large stone monuments, it is less clear that local labor was important to the task. As I mentioned in answer to an earlier question, labor was a form of taxation in the Andes and it is known from the Spanish chroniclers that people often traveled great distances from their home in order to pay this labor tax. They basically went wherever the state told them they were needed and that was often many miles, many, many miles from their own homes.

Question: Were the workers slaves for life or were they allowed to return to their native lands? ~David

Answer: The workers under the Incas and the Andes were not slaves in the true sense of the word. They were actually paying their taxes, and during the rest of the year they lived a relatively free life in their own villages, raising their own food and taking care of the necessities of daily life. They worked on monuments for the state on a seasonal basis and during the rest of the year had their own private lives in their own homes and villages.

Question: Did the Incas trade outside Peru by land or sea? ~Mabel

Answer: One of the things that made the Inca empire so powerful and so great was the fact that the Incas had a genius for connecting various different regions of the country and instituting trade between them. So the answer is that there was an enormous amount of trade going on both by land and by sea up and down the coast of South America. We find products from Ecuador as far south as Chile and Argentina and Bolivia. We find products from those countries as far north as Colombia. We've find products from Amazonian jungles in burials and other locations out on the coastal deserts of Peru. So it is clear that much produce and trade took place all through the Andes under the Inca empire.

Question: What is the latest information on what class of Inca resided in Machu Picchu? ~Rick

Answer: We actually know very little about who resided at Machu Picchu. Earlier in this century when Hirameigham first visited the site and reported it to the outside world, he instituted excavations out of which a number of human burials were found. Many of these burials he believed were female, and therefore he proposed that Machu Picchu was a site favored by the so-called Virgins of the Sun. This was a group of women in the service of the Inca who, according to the Spanish chroniclers, often lived in very special and very isolated locations. Subsequent study of the skeletal remains that Hirameigham found has actually contradicted this and found that there is not a clear evidence that the skeletons are all female, and therefore we really don't know who lived there. Other research, however, has shown that the site of Machu Picchu was probably the country estate of one of the Sapa Inca rulers, probably Pachacuti.

Question: Are the Incas the earliest recorded inhabitants of that area in Peru? ~Aras

Answer: By no means. The Incas did not really exist as a culture until sometime around 1200 A.D., and by 1450 A.D. they began their expansion into an empire that encompassed the entire Andes. That empire was destroyed with the arrival of the Spanish in 1532. However, civilization in the Andes began probably 1000 B.C., and many cultures preceded the Incas and had come and gone prior to the rise of the Incas in 1200 A.D.

Question: Is it possible the Incas could have moved the stone blocks by rolling them over lengths of cordage placed across the route? ~Peg

Answer: I'm not sure what the questioner means by "cordage," although the answer to the general question of how the Incas moved large rocks through the countryside is still under study. We do not have in most cases very clear roadways to indicate the method that was used to transport the stones. We often find ramps in and around the ruin sites themselves, but out in the countryside we find very little evidence of any particular route which we believe was used to move stones, and therefore we really have very little evidence of how it was done.

Question: How do you think they found a true level and vertical? ~Dennis

Answer: A true vertical is of course fairly easy to find by use of a plumb bob, and various devices have been found in excavations at Inca ruin sites which we take to be plumb bobs. In any event, they would be good for that purpose. As far as whether level was important to the Inca, we know that it was because they were masters at managing water in their agricultural complexes. We do not however know how they managed to devise canals, for example at an even grade over miles and miles and miles of country. Clearly some form of leveling was used, but we have no evidence of what it was.

Question: Did the native Andean people eat any distinct food which helped them to better cope with the high altitude air that they work in? ~Bob

Answer: I'm not aware of any direct link between the foods eaten in the Andes and an acclimatization to a high altitude. It is my understanding from medical people in Peru today that the average Andean Indian is born with no greater lung capacity than you or I have, but that by the time they die they may have twice the lung capacity you or I have; in other words, their adaptation to altitude entirely occurs after birth and is not genetically transmitted. As far as what effect the foods they eat would have on this, I really don't know.

Question: I once read that the joints in the Inca masonry walls were made by spreading fine sand between the blocks and then sliding the blocks against one another so that the sand, acting as an abrasive, wore down both blocks evenly. It was also said that there were protrusions on the blocks where ropes could be attached to facilitate the grinding motion. These protrusions were then knocked off after the stone was in place. Have you heard of this technique? What are your thoughts on its veracity? Thanks for your attention. ~David

Answer: An earlier questioner mentioned also the idea of rubbing the rocks together with a sand surface between in order to create the shapes, but where rock walls have come apart and we can see the shape of the joints inside, that seems very, very unlikely. So I doubt that that method was used. It is true, however, that the faces of many of the blocks still show evidence of and in some cases the entire shape of a stone protrusion, several often being along the bottom edge of each stone in a wall. I agree with the questioner that these were designs to be removed and probably were present on many more blocks than we find them on today. I doubt seriously that they were used for the purpose of tying ropes to the rocks in order to move them. For one thing, many of these rocks weigh enormous numbers of tons and they would be almost impossible to move by that method. I think probably most of those protrusions were used as places to apply levers to the stones in order to move them once they were near the positioning which they were intended to be placed.

Question: In an earlier response you talked about the foods that the people ate, but you didn't mention any protein. What was their protein source? ~Lauren

Answer: My earlier response eliminated a major source of protein, and that was the meat of camelid animals. There were two species of camelid animals that were wild under the Inca times and remain wild today, the guanaco and the vicuna. In addition, there were two species of camelid animals that were domesticated under the Incas and remain used in domesticed form by Indians today. That is the llama, or "yama," as it would be said in South America, and the alpaca. Both provided wool and meat and probably cheese of some sort to the Incas in their diet, and all of these in the form of food would have been important sources of protein. Also, as I mentioned earlier, the guinea pig was and remains a major source of protein in the diet of the high country Indians.

Question: One way to fit large stones together would be to create a wooden form that would be lightweight and would fit up against one face of one stone or a section of it. The stone would be smoothed to fit the form. Then another wooden form would be created to fit into that wooden form. The second form, which now fits perfectly into the first form, would be placed against the second stone. The second stone could be polished until it fit the second wooden form. At that point the first stone would now fit into the second stone and would only have to be moved once. ~Marc

Answer: I'm aware of several researchers who favor a method similar to the one proposed by the questioner. Basically it's a matter of templating and using the template, which is presumably lighter and easier to move than the original stone in order to accomplish a trial-and-error fit. The problem with this when large stones are involved is that the template itself must maintain its dimensional stability to a matter of millimeters over surfaces that are in some cases many square meters in extent. It's unknown exactly what materials and methods the Incas had to provide strength and stability in a light-weight form called for by the questioner's method, and, therefore, we think that this method probably was not used.

Question: Is there any evidence that the master stone cutters were highly respected in their society? In other words, were they at the top of their social ladder? ~Julie

Answer: We have fairly good evidence from the Spanish chroniclers that the monuments were largely designed and their construction was supervised by a special class of stonemasons or architects or builders, call them what you will. We have reason to believe that they were respected and held positions of influence in the Inca empire.

Question: Do you know the length and height of the largest span where the ramparts or tie-downs for suspension bridges have been found carved into the rock as you found in the village at the show?

Also would making the side walls higher reduce the likelihood of flipping a bridge like this? The bed of the bridge needs to be relatively taut to provide a path a human can walk across but the looseness of the side rope should have some impact on its stability. Is there any evidence that the base of the bridge and the side walls might be anchored at different levels on any of these bridges? ~Dave

Answer: While I was not part of the bridge-building crew in the particular "Nova" show that we did in Peru, I do know a little bit about the subject. I do not know where the longest span is, although the bridge we did was a fairly long span. If I recall, it was about 50 meters. There may be some longer than that, but I doubt that there were many that were much longer than that. The other thing I would say to this questioner is that the bridge that we built for our show was a relatively small and relatively unstable version of what we are told by the Spanish chroniclers were masterpieces of engineering under Inca times. It is known, for example, that the Spaniards could ride a fully armored horse across some of the bridges in question. It is somewhat horrifying to think of doing that but it tells us that the bridges of the Incas must have been very much more substantial than the one you saw in the "Nova" film.

Additional Q & As
Question: Gold leaf is a very pliable metal. Is it possible that the Incas lightly hammered a thin gold plate onto the receiving stone surface, then lifted it and used it as the pattern for shaping the base of the stone that would rest on it? ~Dennis

Answer: It is true that the Incas had lots of gold, but it is also true that gold is very pliable. Even if they had enough gold to use for the method you suggest, the pliability of the material would have made it very difficult to maintain the shape of the very large joint systems in some of the Inca walls. Also, we would expect to find minute traces of gold hammered into the receiving surfaces, even today when the stones are split apart. We do not find that. For both of these reasons, I think it very unlikely that gold was used as a pattern in shaping stones.

Question: Could the elements of the stones have been sanded down or broken down to powder form, then reformed with water into a square mold left to harden. Ashanti

Answer: This same idea of molding the stones from crushed stone was suggested some years ago by one of the researchers working on the NOVA film dealing with the construction of the great pyramid in Egypt. For somewhat the same reasons we think this method was not used in Peru. The stone used for most of the walls in Peru does not lend itself to reconformation with water into a sort of a concrete-like substance. Therefore we think it very unlikely that any method of this kind was used by the incas.

Question: I am surprised at the lack of inquiry in the idea that the water surrounding the Inca empire wasn't used. They had the means and skill to cause those rounded joints, to hammer away by suspending water and rope. The erosion of the rock is already evident, but seems to have been looked over, the rounded rocks used for cutting are obviously eroded by the river, the mountain terrain would've provided the perfect opportunity to build such a system, divert the water and set up a station at which to erode the pre-determined stone. Am I in blatant misunderstanding or is this a realistic theory? Thanks for any response. ~Steve

Answer: I am not entirely sure I understand your method, but it seems that you are suggesting that the shaping of the stones might have been done by water under pressure eroding the surfaces away. We think this is very unlikely for two reasons. First, the stones used by the Incas were very hard and therefore it would have taken literally eons to make the shape by simple pressure of water against the surface. Second, instead of evidence of water pressure we find the marks left by the stone hammers that the Incas used to make these shapes. For both of these reasons, I believe your method was not used by the Incas.

Question: Are their still places that have not been found left by the Inca. Is their proof that the Inca may have sailed across the oceans and or other people sailed across exchanging information, culture and ideas? If so where can this information be found? ~Carlo

Answer: Yes, there are still places that are found occasionally that were left by the Incas. In fact, my own involvement in the Andes is largely that of an explorer. We often find new ruin sites, particularly in the very thick jungle of the eastern slope of the mountain range, which is otherwise very difficult to explore. It is also true that the Incas had a huge seacoast all the way down the west side of South America and trade took place along that coast by means of coastal boats of various kinds. But that is not to say that the Incas were a seafaring people, and it is very unlikely that they sailed across broad expanses of ocean. We really have absolutely no evidence of contact between the Incas and other cultures in other parts of the world or evidence found in South America of visitations by those cultures.

Question: Vince, I recently (April,1998) had the pleasure of visiting Cuzco to implement a curriculum written by me on the subject of Implementation of Internet for the KHIPU Institute. While there I was given tours of Machu Picchu, Sacsahuaman, Urubamba, Chinchero, and others which I choose not to spell, but I'm sure you know of which I speak. My question is on the "cracking/cutting" of the stones theory. It is my understanding that holes were placed in the rocks. Then branches were placed inside and watered to make them grow, thus cracking the stones. What is your take on this and did you test this method? ~Harvey

Answer: It is true that many of the stones that we find in Inca walls have holes placed in them. We think those holes were used, however, as points for the insertion of levers in the movement of the stones into position. The other holes that we find in stones are sometimes found in the quarry areas where stones will show a line of small pockets that appear to have been chiseled in the stone to receive wooden wedges. We know that this method was used in colonial times to split stones by pouring water on the wedges so they would expand and break open the rock. We do not know whether this method was used by the Incas, however, because many of the stones in the quarries could have been done in colonial rather Inca times.

Question: The straw bridge built in the Inca tradition, how long could it last? Does it rot with the natural conditions of rain? Or does it crack and crumble under the sun's UV rays? ~John

Answer: I was not involved personally in the building of the rope bridge that was filmed during the NOVA show, but I was told that the village that did the construction work repeats it every other year as a sort of village ritual. It was my impression that they felt if it was not replaced every other year that it would become unsafe due to the effects of weather and so forth. Yes, the materials involved were subject to deterioration over a period of time, probably a matter of several years.

Question: I visited Machu Picchu in 1984. At that time, the guide told us that probably the Incas used special herbs to "melt" the stone and give it the correct shape for their constructions. Have you heard about this before? Unfortunately, he explained, no record of which herbs were used to perform this was kept. ~Rocio

Answer: I have heard this same rumor many times that some form of jungle plant was used to melt the stones and give the stone the pliability to create the shapes in Inca walls. I think this theory is nonsense. There are, however, some stones that are more easily worked when wet than dry and it is possible that this particular legend grew up around that idea. It may be that the Incas would wet their stones prior to working them, on the theory that it made the working somewhat easier with their stone tools.

Question: I thought Vince Lee was very correct, also with the tool he used for carving the edges. Could this perhaps have been done, only with the large stones being carved out while laying on their sides-as sort of a jigsaw puzzle, and then erected AFTER all the sides had been carved and smoothed so perfectly. Moving them with more of the ease as was shown in the moving of the large stone by the townspeople AND the use of the tool? ~Jimie

Answer: This would be a good idea. In fact in my practice as an architect in Wyoming, we often build log cabins this way today. That is to say, the logs are fitted together elsewhere, numbered, taken apart, and re-erected on the site. There are two reasons why we think this was not done with the great stone walls of Peru. First, one would expect to find evidence of stones being fitted either at the quarries or around the grounds of sites that were abandoned while they were under construction, and we do not find this evidence in either of those two places. Also, we would expect to find the tops of walls which were left unfinished—nevertheless, carved to receive the stones that were to be fitted above them. And instead we find that the tops of the walls which were left unfinished are raw, natural shapes, strongly suggesting that the next course was to be fitted in-place rather than elsewhere.

Question: What evidence, if any, suggests that the Inca civilization had the same environment as we see today? Is it possible that melting glaciers or other natural weather forces played a part in the material handling aspects of building some of the Inca structures, and/or aided the Incas with water and food supplies? ~Steven

Answer: It is my understanding that there is no strong evidence that the climate in the Andes was much different in Inca times than it is today. However, it is true that the glaciers in the high mountains that are found all through the Inca empire were probably much larger in Inca times than they are today, because the glaciers of the world have been in a period of recession ever since those times and even today we find that in a matter of 10 or 15 years the size of a glacier is reduced considerably. That in turn means that there may have been more water flowing from the larger glaciers into the creek systems in the Andes during Inca times than there is today. But we do not have evidence that the weather or the climate was otherwise very much different than it is now.

Question: Was it fun being there and building the bridge? I enjoyed the show. ~Liat

Answer: Yes, it was a great deal of fun doing the entire project with NOVA. I was not one of those who helped build the grass bridge since I was busy chopping on stones in a different location but I know that the people who built the bridge had a great time doing it and I certainly enjoyed the part I played in building a little piece of an Inca stone wall.

Question: How elaborate were the Incas involved in directing water to their settlements for plumbing and other purposes? Did they rely on going directly to the water sources like streams, lakes and rivers? Or did they have a somewhat elaborate public works system? ~Peter

Answer: The Inca civilization was basically agrarian like all pre-industrial civilizations so that the production of food was one of the central projects managed by the state. For this reason in the high, dry Andes water management by the state was very, very important. So a great deal of water management went on in the Inca empire. We have found canals, dams, reservoirs, and almost every ruin site of any consequence will have one or more baths and a number of fountains. It is very clear that water management was important to the Incas.

Question: Would it have been possible for the Incas to have a slide made of logs to pull them across the valley to where they would be used? ~Jess

Answer: It was certainly possible for the Incas to make slides of some sort out of logs in order to move large stones. The one excavation that we did during the NOVA project at Ollantay Tambo did not show any evidence of this, but that's not to say it wasn't done. When we were on our recent project on Easter Island it became clear that where very large stones are involved it would almost be necessary, almost unavoidable to use log sleds of some sort and I think it is probable that the Incas did the same thing. We have not yet found any firm evidence of it.

Question: With respect to that mirror theory, you mention that you have seen no evidence of melting of rocks anywhere. I saw a program on a show called "Timeless Places" and it showed interesting pictures of some rocks at a quarry in Q'enqo that look remarkably like they were melted. There are sections of rock that look like someone was testing some tool (they looked similar to scribbling with a ball-point pen when the ink dries up). The pictures were quite startling. Are you familiar with these features? and do you have any explanation?

Other conjecture mentioned was about a place (I forget where) that may have had a room that was lined in gold which may have formed some kind of capacitor. This is a little bizarre, but quite intriguing. They conjectured that they could see possible evidence of some kind of control box. Some power source may be possible, but thanks to the conquistadors, we may never know.

Also shown at Q'enqo were blocks of stone that were in mid-excavation, and there were these large (18" dia) bore holes around the block. Could these bore holes be made using the hammer stones? ~Kelly

Answer: I have been to the carved stones in Q'enqo in the hills above Cuzco a number of times but I must confess I have not seen or at least did not notice the specific features you mention. The idea nevertheless that the Incas somehow melted stone in order to accomplish fitting or carving seems far-fetched to most of us who have studied their techniques. For one thing we find evidence everywhere of peck marks on the stones indicating that the cuts were made by other stones rather than by reflected heat of concentrated heat. Another way to look at this is if the Incas indeed had some sort of technology for concentrating the heat of the sun, it is almost certain that the Spaniards would have reported it. They arrived after all almost at the height of the Inca empire although the Incas had recently suffered some setbacks in the form of civil wars and an outbreak of small pox or some other European disease that had come down from Mexico. Nevertheless, their culture was as its high point. Surely, had such a technique been used by the Incas it would have been reported by the Spaniards. Another way to look at this is as one of the researchers on our NOVA project in Peru said at the time, if the Incas had a way to melt stone was reflected solar energy, why didn't they simply melt the Spaniards out of their saddles when they were attacked by the conquistadors.

Question: Is it possible that the Inca builders planned the placement of each stone so well in advance that they were able to fit the stones while they were still in the quarry? Then each could be moved to the site and placed together like a jigsaw puzzle piece. ~R.M.

Answer: I assume from the wording of your question that you believe the Inca stones were quarried from a mountainside, chopped out of the mountainside in some sort of order that could then be reassembled in their walls. The fact of the matter is that with very, very few exceptions the Incas simply took boulders from boulder slides at the face of cliffs and on mountainsides and shaped them for their purposes. That is to say the boulders were not together in the mountain before they were used by the Incas and therefore it seems very unlikely that the Incas reassembled adjacent boulders in their walls.

Question: Could the largest stones have been fitted by scribing the seat to a casted copy (supported by timber lattice) of the faces of the stone? It would weigh MUCH less, and could be designed with lashed "legs" for safe positioning & working under. With accurate reference marks, it might even be done in sections. ~Gordon

Question: Could the Incas have made mud castings of the surfaces of the stones as templates for the fitting? I believe that the method you used was too tedious and unreliable for such incredible results. ~Tom

Answer to the two previous questions: Both deal with templating of the stones being fitted. I should expand on my answer to cover this and other similar questions that we have received in the last few days. There are really only three ways to accomplish the fit that we see in Inca stone masonry. One is trial and error involving many movements of the stone until, by small increments, the fit is achieved. The problem with this with very large stones is that moving these very large stones many, many times would be horrendously difficult, dangerous, and the likelihood of chips and errors being made would be very high. We do not find evidence of such chips or errors on any of the edges or faces of the stone. The second method would be templating wherein a lightweight but otherwise perfect facsimile of one of the stones would be substituted for the stone itself and then a trial and error operation would ensue which would avoid the the necessity of moving a very heavy stone. This might have been done for small stones but for the large stones of Sacsahuaman, the template itself would be monstrous. Many of them would be much larger than an automobile and it is unclear to us what material or method the Incas had to produce such a template. After all, it would have to be both light weight and strong enough to resist the stress of many, many movements and it would also have to be dimensionally stable. If it were made for example out of wood, it would tend to shrink as the wood dried out and yet we find that the stones fit to tolerances sometimes of less than a millimeter. It is very unlikely that the Incas had any way of making such a large object strong, light enough, and so dimensionally stable that they could accomplish this. These two alternatives being eliminated, the only one left, it seems to me, is scribing. My method is a way of using scribing but it may be that there was a better way of using the scribe than the one that I have so far been able to come up with.

Question: The Incas were serious mathematicians, they knew numbers, they used the Quipu, which is an elaborated little machine made with ropes, and knots, different lengths and sizes, well my theory is that they calculated every single man, and size and position of every single stone can you explain on this? ~Brunella

Answer: It is true that the Incas had a fairly advanced system of arithmetic and they used numbers for the recording of many things. However, applied to the fitting of stones it is difficult to see how numbers would have been of much help because the stones are not dimensionally accurate. They are not square, there are no right angled corners, and there are no flat planes. They are basically all odd shaped, on of a kind volumes. It is very difficult to see how a numerical system could have described such shapes in any way that would be helpful to the stone fitters.

Question: I was wondering if all Inca walls and or monuments are just 1 layer thick? you talk like they are. this may be a flaw in their flawless seemingly process. the Egyptians had many layer thick pyramids, yet the Inca didn't? maybe this is a flaw in their design because it was only designed to fit the first 3-4 sides of the rock, and not lass 6 sides... ~Brian

Answer: It is true that most of the walls that we see in Inca buildings are either retaining walls which have only one finished face (the outer face) or in some cases they are the walls of buildings in which case either one large stone is finished on both sides or in some cases stones are put back to back so that only their outer faces are finished and their inner faces (inside the wall) are left rough. This is really not unlike what was done by the Egyptians. It is true that the Egyptians had very heavy, thick structures with very thick walls, the pyramids perhaps being the ultimate example. But it is also true that the fit of the stones inside the pyramid is very rough. Only the finished surfaces, whether it be the exterior of the pyramid or the interior faces of the spaces within the pyramid, were really finished very finely. All of the joints inside between those fitted faces are actually quite rough, not unlike those of the Incas.

Question: Is it possible that the Inca people lifted up the stone blocks onto the rest of the wall by a system of ropes and pulleys, or would they not have that technology yet? ~John Eric

Answer: There is absolutely no evidence that the Inca people had the use of the wheel or the pulley in any sense that would have been helpful to erecting monuments. The use of the pulley was actually a fairly late invention even in the old world but does not appear to have ever been found in the new world prior to the arrival of the Spaniards.

Question: My husband & I greatly enjoyed the program on Inca stone masonry. We agreed with Jean Pierre that the individual with the parabolic mirrors was a total idiot.

In discussing the question of how the stones were set together so well, especially the very large ones, Jim came up with a thought. The large stones cannot be moved easily to continually test the set. Perhaps a substitute was used. If a grass & mud mold were to be made of the large stone, one could cast a lighter version of the stone (perhaps also in grass & mud) with which one could use to fit the stone setting. One need not cast the whole stone but only the corner being set. At first I thought any detail would be lost in the casting, but then I thought about how bronze figures are cast.

Is there a possibility that castings could have been made of some local material that would have allowed the detail of the stone to be preserved? ~Joan

Answer: I would refer you to the rather long answer I gave to one of the earlier questions. All questioners trying to find an alternative to scribing for the fit should consider that the joint involved is one large plane all of which must be fitted at the same time. You cannot fit the bottom first and then fit the rising face next to it. You cannot fit the corner first and then fit the faces adjacent to the corners later. The whole joint must be fitted at one time so that any template used for the purpose must be actually as large as the entire stone or at least the fitted faces of the stone being fitted.

Question: Isn't there a group of Inca descendants that might know about the Inca architecture—about the Incas not having the wheel, metal tools and so on? How much of a fact is that? ~ McLan

Answer: The Incas were actually one of a large number of tribal groups living in Peru at the time of the Spanish conquest. All of the Indians in the Inca empire were not, strictly speaking, Incas. We know of no one today that can really claim a direct descent from the Incas themselves, although there may be such people. In any event, no one today knows anything about the happenings in the Inca empire prior to the Spanish conquest other than what we have written down from that time by the Spaniards. We do also know quite definitely from the Spaniards who arrived at the Inca empire pretty much at the height of its culture that they did not have wheels, iron, steel, or a written language. They did have some metal tools made of bronze and we have found crow bars and occasional chisels. Unfortunately the chisels are generally somewhat softer than the rocks with which the Incas built their buildings, so we do not think those chisels played a major part in Inca construction techniques.

Question: How much land did the Inca kingdom covering square Kim's? How many tons would the largest building blocks be? ~John

Answer: I have no idea what the square kilometers covered by the Inca empire were at the time of the conquest, however I think you can figure this out yourself by referring to an atlas. The Inca empire at its height extended from southern Columbia all the way down to central Chile and from the Pacific Ocean to the toe of the eastern slope of the Andes at the head of the Amazon basin.

As for the largest blocks used by the Incas, the largest block I'm aware of is probably in the ruins of Sacsahuaman near Cuzco and it is reputed to be nearly 300 tons.

Question: Has anyone been able to replicate the Incas' ability to position stones together with seams so tight that a razor blade cannot penetrate the seem? Do we know how they managed to do this with their "primitive" technology? ~Miguel

Answer: Yes, several of us researching this question of how the Incas built and fit their stones so perfectly together have achieved good results with methods that we proposed were used by the Incas. A good friend of mine, J-P Protzen who appeared in our NOVA film has done very good joints in small stones of the size that can easily be handled by one or two people and we achieved a fairly good joint in a large stone measuring several tons in weight. Nevertheless, there is a lot more to be done to prove that we know exactly how the Incas did this.

Question: I have seen on TV that hot air balloons could have been made from local materials in the vicinity of the Inca empire's boundaries. Could a team (10 - 15) of these balloons plus ground-based manpower have lifted the stones across the river and up to the sun temple? If the balloons let the stones hover in midair, that would also enable precision carving. (name withheld)

Answer: I doubt very seriously that hot air balloons were used by the Incas prior to the Spanish conquest or for that matter afterwards. We have no evidence from any source of this. It is also true that the lifting power of a hot air balloon is relatively slight, amounting only to the difference of the weight of the gas in the balloon and the weight of any equal volume of air. With this in mind, it would take a balloon the size of Mount Everest to pick up some of the stones that we see in place today.

Question: THEORY ONE: I understand that the Incas did not have the wheel and modern block and tackle but even ancient cultures used something like a "gin pole" to provide leverage and act as a hoist to lift things.

THEORY TWO: It occurs to me that an overhead grasp of these large rocks would provide the underside access that the method shown on the program did not. It would also provide the control to list, hoist and adjust that the manual method did not.

THEORY THREE: The notches on the lower edge of the rocks I can visualize as grapple points but I think a tool like an "ice tong" that has a center fulcrum and curved or pointing up tips might have provided the grasp that the sticks from below did not. Would a forked branch with a long leg and a short tip used in pairs be the kind of tong to grasp a rock from above? The weight of the object tightens the grip until you lower the gin pole or hoist and remove the pressure.

THEORY FOUR: The Incas obviously had rope technology. I think I have even seen examples where raising and lowering an object was probably used so they must have had crude open hole block technology. If you look at the Phoenician, Egyptian, Greek, Malaysian boats and the RA and the Kon Tiki they all had some block technology to change pressure on a line. Even a three hole block provides a tremendous amount of lift. Four or five hundred years ago there were sailing boats with this kind of technology. Certainly a culture this advanced would have been able to grasp the concept.

THEORY FIVE: I am not quite ready to accept the parabolic mirror theory as a construction tool but they may certainly have provided some communication between way stations.

THEORY SIX: As we know, the wet rock provide a very able path to move the stone. The Inca had many waterways. The cobbles provided a bearing surface with significantly less friction than the bare dirt. We know that there appeared to be a roadbed under the stone that was moved. On top of the roadbed there was grassy material. Have you ever walked on wet grass on a surface that had little friction? You may remember what the sky looked like while you were lying on your back. What is to say that they did not lubricate the grass on the cobbles with water, mud, or manure to move the gigantic stones?

THEORY SEVEN: Incidentally sliding these large rocks on a cobbled surface would be like rubbing wood on sandpaper. It would leave a smooth, abraded surface. ~Dave

Answer: There are a number of things included in this question but they all generally hinge upon the idea that the Incas perhaps had some sort of primitive rope technology such as gin poles and ice tong lifters and so forth, all of which were commonly used in medieval Europe. Again, the Inca empire was pretty much at its cultural height at the time of the Spanish conquest even though there was social unrest and some of the major building projects had probably been canceled by that time. There is no evidence from any Spaniards who have witnessed Inca technology of the use of any form of pulley or gin pole or ice tong lifter and therefore we doubt seriously that these things played much of a part in Inca construction prior to the introduction of those techniques by the Spaniards. It is also true that the rocks we are talking about are so large that even if the Incas had such technology it would have been enormously inadequate to the task. On our recent project on Easter Island (see Secrets of Easter Island) we needed a huge steel crane to pick up a rock weighing only 10 tons. I am not aware of any crane even today that could pick up a 300-ton object. There may be one, but it certainly couldn't be made from poles and ropes and the sorts of things that you propose might have been available to the Incas. You also suggest as does one other questioner that lubricating a road bed might have played a part in moving Inca stones and I'm fairly sure that's true. Unfortunately today we have very little evidence of this. Even where we excavate the roads we find nothing other than rocks but it is almost certainly true that grass and liquids of various kinds and perhaps as you suggest smooth, round stones were used very effectively to lubricate road beds for moving heavy objects.

Question: On the show I saw tonight regarding the magnificent building that were made of stone fitted together. When pulling the heavy stones up the steep grade and then down the steeper grade, why couldn't they have used the weight of the stone going down to help pull up the stone on the other side of the top? It might also help control the speed of the stone going down. If they could get a small stone to the top, they could use it as a counterweight for the next stone which could be heavier. If they used progressively heavier stones, it wouldn't take a much man effort to push the stone up and it would really help the stone going down as it would be counterweighted by a heavier stone going up. ~Peggy

Answer: You propose that the stones moving down a grade on one side of a hill might have been used to counter-balance and even help lift stones up the hill on the other side. I doubt seriously that this is the case because the stones are so large and the frictional surfaces against which they bear so great that there is very little force (even in the case of a stone moving down hill) applied on the ropes lowering it. It is also true that at Ollantay Tambo the stones generally move downhill from the quarry and uphill to the ruins so that we didn't really have the opportunity to apply the principle that you are suggesting.

Question: I noticed in the program that the easiest way to transfer a rock was through the stream bed. Stone on "wet" stone. Have you considered that the Incas may have wetted the stone and slid the rock over the trail. Or even yet, transferred the stone over wet straw on wet stone roads. You may find that the coefficient of friction is much less than dry stone on dry stone. ~Roger

Answer: This also deals with the question of transferring stones on a wet cobblestones or other lubricated surfaces and we are fairly certain that this wasn't the case although we really have little evidence to prove it at this point in time.

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