Episode 28: The Stars in Stone

April 6, 2023

We turn the clock back to the astronomy of the Paleolithic and Neolithic. Clues about humanity's interest in the heavens during the Paleolithic can be seen in linguistic, mythological, and archaeological evidence. In the Neolithic, groups of people constructed tens of thousands of megaliths across Europe, many of which had astronomical connections.


Good evening and welcome to the Song of Urania, a podcast about the history of astronomy from antiquity to the present with new episodes every full moon. My name is Joe Antognini.

Well, as you can perhaps gather from the title of this month’s episode, I am afraid that I have once more bamboozled the poor listeners of this podcast. Despite my promise from the end of last episode, this episode will not be about Egyptian astronomy. As I was researching it, I found that most of the book length treatments are fairly old at this point, going back to the 50s and 60s. However, one of the leading experts on Egyptian astronomy, Juan Antonio Belmonte has a new book coming out on Egyptian astronomy at the beginning of May. So I figured it would be worth postponing my episode on Egyptian astronomy for a few months to wait for his book to come out so I can use the latest research and so that you, dear listeners, can get the most up-to-date story.

So what will I be talking about instead? This month I wanted to talk about the oldest astronomy we are aware of, the astronomy of the Paleolithic and Neolithic. But before we really get into it I want to take a step back and give you a high level outline of where I’m planning on going over the course of this podcast. So far we’ve looked at the astronomy of the cultures of the ancient near east and Mediterranean: the Babylonians, the Greeks, and the Romans. And as I mentioned, we’ll get to the Egyptians in due time. But what I would like to do next is cover the rest of the ancient world. My plan is to very loosely follow expansion of mankind out of Africa. So after learning about Paleolithic and Neolithic astronomy in this episode, we’ll then look at the astronomy of sub-Saharan Africa, followed by the astronomy of India, then the astronomy of China and east Asia. Then we’ll move south to the astronomy of southeast Asia, followed by the astronomy of Oceania. After that we’ll cross the Bering strait and look at the astronomy of the pre-Colombian Americas, in particular the Mayans, whose astronomy was one of the most sophisticated of all the ancient cultures. And by now, of course, wise listeners of this podcast should know to take any grand plans that I lay out with a grain of salt. So we’ll see what actually happens. But that’s the plan for now.

In terms of chronology, these episodes will flit back and forth across the centuries much more than we may have become accustomed to. In my treatment of Greek astronomy we were able to go roughly chronologically from the Archaic period starting around the 8th century BC up to Ptolemy in the Roman period in the 3rd century AD. But across the globe different cultures flourished at different times, so we’ll be ranging from the prehistory of 100 thousand years ago to the 16th century AD and on occasion somewhat beyond.

One other caveat I should mention is that while I would like to devote as much time to each one of these cultures as I did to Greek astronomy, it may not be possible in most cases. I may be able to come closer for some than others. But unfortunately whether or not a culture developed writing makes a tremendous difference in the amount of surviving material available to discuss. We saw that even with the Greeks, who left behind a tremendous written record, we had to do a lot of speculation and cross correlation to make up for the huge number of missing texts. When studying cultures that left no written record at all, our understanding necessarily becomes much, much more speculative.

Once we’ve worked our way around the globe, we’ll pick up the thread to modern astronomy once more by transitioning from the end of antiquity to the early middle ages with the rise of Islam in Arabia in the 8th century. From there on, our focus will be largely Western, at least until we get to the 20th century, when cultural contacts between the West and the rest of the globe deepen to the point that the forefront of astronomical research becomes a global rather than a purely Western project. Needless to say, this whole affair should keep us all occupied for the next few years to come.

Okay, with that broad overview of where I want to take the podcast, let’s get back to the topic of this episode. This month I want to explore the very earliest evidence we have for mankind’s interest in the heavens during the Paleolithic era, and then we’ll see how later on in the Neolithic this interest was articulated with the megalithic structures that dot western Europe.

Now before we get into any of the concrete evidence we have for early humanity’s interest in astronomy, it’s worth outlining how we know what we know about it, as little and speculative as it is. Prehistoric peoples are exceptionally difficult to study because by definition they lack writing, so they never just told us all about themselves in the same way that the ancient Greeks, or Egyptians, or Chinese, or Mayans did. But there are other ways that ancient cultures leave a record that we can learn from. The most direct means is from archaeology. This can be in the form of the impressive monuments that some cultures built like the pyramids of Egypt or Stonehenge in Britain. But smaller, more quotidian artifacts like pottery, arrowheads, axes, and so forth are an extremely valuable record. By looking at how artifacts with similar styles spread across continents we can trace how groups of people migrated over the millennia and where they settled. Another means by which we can trace the movements of people is through genetic analysis since the relics of these movements persist in our genes right down to this day. Most people throughout history never really moved more than a few dozen miles from where they were born, and this is still true today, though the majority is somewhat smaller than it was centuries ago. Since genetic patterns drift at a rate that can be fairly well determined, by comparing the genetic similarity of two populations you can figure out when the two populations diverged from each other. The genes of modern day people act as a kind of living fossil of their earlier migration histories. These kinds of genetic studies show, for instance, that modern Europeans are largely a mixture of three waves of people: Western Hunter-Gatherers, who were originally present in Europe at the end of the Ice Age around 10,000 BC; a group called the Early European Farmers, who originated in Anatolia around 20,000 years ago and then spread into Europe between 10,000 and 4000 BC; and a third group called the Western Steppe Herders who probably originated in the area around modern day Ukraine, southwest Russia, and Armenia and who rapidly spread across Eurasia between 3000 and 1000 BC, reaching as far as western Europe, Persia, India, and central Asia.

In addition to archaeology and genetic studies, there is yet another, older way to trace population movements. In the same way that we inherit genes from our parents with some number of mutations, we also generally inherit our parents’ language, and will change it very slightly. By comparing the languages of neighboring groups, historical linguists can also trace migration patterns. Languages don’t evolve totally randomly. Linguistic change tends to follow certain patterns. Certain pairs of phonemes are more likely to be substituted for each other, some phonemes in particular clusters are likely to be dropped over time. A shift in the sound of one vowel has a predictable effect on the sounds of other vowels. And these forces of random drift act more strongly on some parts of language than others. We are liable to change rarer words more quickly than more frequently used words. A small set of words that are very fundamental to the human experience change only very slowly. Words like “mother,” “tree,” or “bird,” maintain similarities across centuries, if not millennia. The word for “mother” in Punjabi, which is very distantly related to English, but is in the same language family, is “māṁ.” Just as our genes are a kind of living fossil we store in our bodies of earlier migration patterns, the languages we speak are a kind of fossil we store in our minds. In fact, the first evidence for the migration of the Western Steppe Herders from Europe to India came long before Gregor Mendel founded the study of genetics in the mid 19th century. Philologists in the early 19th century noticed linguistic commonalities across European, Iranian, and Indian languages and hypothesized that these hundreds of languages must have derived from some common language. Today, we call this language Proto-Indo-European, and associate it with the language of the Western Steppe Herders.

Historically, people have tended to treat linguistic evidence of population movements a bit suspiciously. It’s always been a kind of ugly stepchild next to genetic studies, which is the gold standard. Historical linguistics tends not to have same level of rigorous mathematical modeling that genetic studies do. You just sort of imagine a linguistics department being a long corridor of offices with a professor in each one going “ga ga ga, ta ta ta, la la la” to themselves all day long and then writing up a paper on how Hungarians originated from western Siberia and split from that group in the 4th millennium BC. Being married to a linguist, I can tell you that, while I’m being slightly facetious, this conception is not too far off the mark. But nevertheless, linguistic methods seem to work. Most of the major population migrations were initially proposed from linguistic evidence and only later confirmed through genetic studies.

It’s from linguistic evidence in the Proto-Indo-European language that we can see some of the early interest in astronomy of the Western Steppe Herders. I mentioned in an earlier episode that in English the word “month” is etymologically connected to the word “moon,” and “menstruation.” But this connection is not unique to English. It appears generally throughout the Indo-European language family. This suggests that the identification of a time period associated with the cycle of the Moon, and a connection between the length of this cycle and the menstrual cycle goes all the way back to the Western Steppe Herders of the Neolithic Era. In other words, Neolithic people were observing the heavens and connecting what they saw above to what they experienced on the Earth.

There’s a yet more abstract way that cultural memories persist through the centuries, and this is through folklore and mythology. In the same way that linguists have systematically categorized the sounds of languages and studied how phonemes tend to drift, ethnographers have collected and categorized folk tales across different peoples and measured their similarities. Here we are yet another step away from mathematical rigor, but there is nevertheless very compelling evidence that, like language, folktales tend not to change very quickly. One folktale, really more a family of similar folktales, called the Smith and the Devil, has variants across the Indo-European languages, and has been traced back to be at least 6000 years old.

Well, one of the richest sources of mythology is, of course, the heavens. In the Western canon the myths associated with the constellations all derive from Greek culture, but every culture has mythological stories associated with the heavens. This on its own is highly notable. Human cultures vary wildly across the globe, so much so that any kind of cross-cultural universals are rather rare and must tell us something that is more fundamental about humanity. So, taking an interest in the heavens appears to be a universal of the human condition. And there is some very intriguing evidence that this interest goes back very far back into humanity’s past. One of the most remarkable features on the sky is the Pleiades star cluster. The Pleiades is an open star cluster somewhat close to the celestial equator, so it is visible to every people on the planet and being visually impressive, virtually every culture has a myth associated with this object. In Western astronomy, this myth is Greek in origin and tells of how there were seven sisters, born from the god Atlas. After Atlas was condemned to carry the vault of heaven on his shoulders, these catch the eye of Orion. Being unprotected by their father, Orion pursues them and they ultimately commit suicide, whereupon Zeus placed them in the heavens. But later on, one of the seven, Electra, became so distressed after seeing the destruction of Troy, she let down her hair in mourning and became invisible, or in other tellings, a comet that then fell from the sky. Among several Aboriginal groups in Australia there is a similar story. The Wirangu people of southwest Australia identify Orion as a hunter named Tgilby. Tgilby falls in love with seven sisters and chases them. Among the Cheyenne in North America, the daughter of a chief was visited by a strange man, who turned out to be a dog in human form. She later gave birth to seven puppies who were placed into the heavens.

Across the globe, these stories have a common feature. A large majority of them identify the stars with seven things — seven sisters, seven puppies, seven boys, seven chickens and so forth. But there is a problem. If you go outside and actually count the Pleiades, there are only six of them. The cluster itself has many more stars, of course, but you can only see six with your naked eye. So why do most cultures have a myth in which there are seven Pleiades? What is especially intriguing is that many cultures have a story in which there were originally seven, but one of them got lost along the way somehow, like in the Greek myth with Electra. Another example comes from the Cherokee who say that there were once seven boys who only wanted to play and would not do their chores. One day they were running around in a circle and they spun around so fast that they all rose up into the sky. But as they were rising, one of the boys was too slow and fell back down to the Earth. Now, as it happens today there are two bright stars in the Pleiades which are very close together, so we cannot distinguish them by eye. By eye, they appear to be one star. But stars all have random motions, called proper motions, and if you reverse the motions of the stars in the Pleiades you find that about 100,000 years in the past these two stars were far enough apart to be distinguished and people would have counted seven stars in the Pleiades. If this is the real origin of the preponderance of myths in which the Pleiades is identified with the number seven, then it suggests that humanity’s interest in astronomy dates back very early into our history.

Another intriguing example of the long history of astronomical mythology has to do with bear myths, and in particular so-called “Bear Son” tales which appear across the Northern Hemisphere, from western Europe across Siberia all the way to North America. Many of these cultures have a special reverence for bears. People have been awed for millennia at the strength of bears and their ability to go months through the winter without any food or water, and many groups have even claimed that they are descended from bears.

The Spanish linguist Roslyn Frank once told a story of how she came to learn of the special reverence that the Basque held for the bears.

Many years ago, when I first decided to do fieldwork in [the Basque Country] it quickly became apparent to me that I would need to learn [Basque]. Soon after I had gained enough proficiency in the language to carry on a basic conversation, a strange thing began to happen to me. People would take me aside and tell me the following in a low voice, as if they were sharing a very important yet almost secretive piece of knowledge: “We Basques used to believe we descended from bears.” The first time someone told me this, I had no idea what I should say in response. I found the statement totally amazing. Yet over and over again the same thing happened to me. People, who didn’t know each other, who had no contact with each other, ended up telling me the same thing.

These cultures have a family of similar folktales which are called “Bear Son” tales. The general shape that these stories take is that a hero is descended from bears. Either he is born of a bear and a woman, or perhaps he was abandoned and was raised by bears. Either way, he grows up with bear-like strength. Then he assembles a group of warriors who defend some place, perhaps a home, a town, a castle, or a land, after some sort of monster attacks it. He is able to injure the monster and chase it away, and then pursues the monster all the way underground or perhaps even to the netherworld. In the Western Canon, the most familiar Bear Son story is a portion of an Old English epic poem entitled Beowulf. Beowulf is, of course, the hero, and while he isn’t born of a bear, his name probably derives from the old English “bee hunter,” which is a roundabout way of saying a “bear” since bears have been known since ancient times for raiding beehives for honey. And this kind of roundabout way of saying “bear” is not unusual for these cultures. One of the indicators of the respect that ancient peoples paid to bears is that many languages did not directly refer to them. To name a bear directly was a kind of taboo and the word would be avoided lest by saying its name, a bear might appear. So in Germanic languages, English included, the word for bear ultimately derives from the word “brown,” a bear simply being the “brown one.” At any rate, Beowulf, the bear warrior, and his companions do battle against the monster Grendel who has attacked a great hall. After defeating Grendel, Grendel’s mother next attacks the great hall, killing one of Beowulf’s companions. Beowulf and his men then track her down to her lair whereupon he kills her in a great battle.

Well, the mythology around bears in these northern cultures is not limited to terrestrial stories. Most of these groups interpret the constellation we now call Ursa Major, the Great Bear, as a bear and have similar stories explaining how this group of stars came to be. The general pattern is that a group of hunters were chasing a bear and the bear escaped into the heavens. These stories exist for dozens and dozens of cultures, from the Basque in northern Spain, to the Siberians, to the Ojibwe of the Great Lakes region, the Iroquois of Northeast America, the Inuit of Alaska and northern Canada, the Tlingit of the Pacific northwest, and the Pueblo of the Southwest.

The similar folklore around the constellation Ursa Major from the Basque to the Iroquois suggests that these tales were probably in place before these groups split up, which would date the association of this group of stars to representing a bear as being at least 13,000 years old.

So, from linguistic and mythological evidence, the similar etymology of moon, month, and menstruation, along with the Pleiades and Bear-Son myths we can reasonably conclude that humanity has taken an interest in the heavens and made a connection between what they saw above to the world around them certainly at least 10,000 years in the past, and very probably much, much earlier than that as well. Now you might quibble with how much stock we should place in any one of these lines of reasoning. You could argue, for instance, that something about the Big Dipper looks inherently bear-like to the human brain and that all these northern peoples independently came to describe the asterism as a bear long after they had split up. But at the same time, I think we are all familiar with what bears look like and what the Big Dipper looks like, and let’s face it, the two don’t really resemble each other all that closely. And in point of fact, many cultures which broken off even earlier have different associations with this grouping of stars. In China and Japan the stars were seen as a dipper, which is a much more logical interpretation of these stars. In southeast Asia it is seen as a kind of crustacean, a shrimp or a lobster. At any rate, I think it’s fair to say that while none of these pieces of evidence on their own may be conclusive, taken together, the case for a long history of interest in the heavens is a lot stronger.

A thornier question is why this interest developed in the first place. And this question is really just one question from a whole class of questions not just limited to the development of astronomy. It is very difficult to disentangle cause and effect when understanding the development of civilizations. Did population clusters arise because of the development of agriculture? Or were the population clusters there to begin with and those clusters facilitated the development of agriculture? In the 19th and first part of the 20th century the standard story was generally that agriculture came first and allowed the growth of population clusters that otherwise couldn’t have been supported. But today the story isn’t so clear. The very earliest settlements known like Gobekli Tepe in Anatolia have evidence that they predated agriculture and were not continually inhabited, but perhaps inhabited only seasonally. So it’s possible that early population centers were places where disparate tribes would intermittently gather to trade, perform religious rituals, and intermarry. Maybe over time some people stayed in that area for longer periods of time until it became their permanent dwelling. Since people would bring high quality food from a wide region perhaps some of the seeds would be sown in the area at first accidentally, and then later more deliberately, and these regions would have become proto-farms. At any rate there are many different kinds of stories that have been told about the development of civilization and it’s tricky to unambiguously rule out all but one story.

So with the development of astronomy, one story that has been told is a very practical one. People needed to keep track of the seasons to know when to reap and sow if they were agricultural, or to track animal migration patterns if they were hunter-gatherers, and astronomy was the means of timekeeping. This motivated their interest in the heavens. In this story, the mythological stories perhaps began as a kind of mnemonic device. But another, equally compelling story you could tell was that the early interest in astronomy was fundamentally religious and that its later use as an aid for agriculture or hunting was a later accretion. And, truth be told, trying to separate out these two stories might be a hopelessly modern kind of project. In the pre-modern worldview separating the migrations of animals and the natural cycle of the seasons from their religious attitudes just may not be possible.

Well, in addition to this kind of linguistic and mythological evidence for prehistoric astronomy, as I mentioned earlier there is also more tangible archaeological evidence. And for the rest of this episode I’m going to focus on the archaeological evidence we see in Europe. We’ll focus on other areas of the world in later episodes.

There are two main kinds of astronomical artifacts we see in prehistoric Europe. One is prehistoric art, and the other is in the megalithic structures that dot the continent.

The prehistoric art of Europe tends to be both older than the megaliths and also more enigmatic. One of the older pieces of art is a work that is today called the Venus of Laussel. It’s a bas relief carving into limestone in the southwest of France that is estimated to be about 25,000 years old. Since it has no organic material it can’t be dated with carbon-14, so the date comes from comparing it to other artifacts in a similar style. Archaeologists and anthropologists have identified a number of distinct paleolithic cultures that inhabited Europe from 50,000 years ago until the Neolithic. The Aurignacian was one of the oldest, and the Magdalenian one of the newer cultures. Somewhere in the middle, at the height of the Ice Age, around 33,000 to 17,000 years ago was the Gravettian culture, which spanned Europe from Portugal to Poland, with some sites being found even as far east as Moscow. This culture is particularly known for its fondness of what are called Venus figurines, small statues of a woman with exaggerated features, wide hips, a large abdomen and large breasts, and narrow or even missing arms and legs, and oftentimes no face. The Venus of Laussel neatly fits into this stylistic pattern except that in one of her arms she is holding something in the shape of a horn or crescent. This horn has 13 notches in it. Now, as with all Paleolithic art, we really have very little context to interpret the work, so any interpretations are necessarily highly speculative. But at least one interpretation is that the crescent shape she is holding is suggestive of the crescent of the Moon. And the number 13 would then correspond to the number of months or menstrual cycles in a year.

A much better known and very impressive site is the Lascaux caves, also in southwestern France. These caves contain some 600 paintings dating back around 17,000 years. They mostly depict large animals, bulls, bison, an ancient relative of cows called aurochs and so forth. But intriguingly, some of the animals additionally have dots nearby. One of the most suggestive of these is a bull who has a cluster of six dots above his shoulder, along with a cluster of dots on his face. The placement of the dots on the bull, along with the shape of their cluster and his overall position highly resembles the constellation of Taurus, with the cluster of six dots above the shoulder representing the Pleiades star cluster and the cluster of dots on the face of the bull representing the Hyades cluster. But most intriguing of all in the Lascaux caves is a set of paintings in a deep shaft, separated from the rest of the complex. These paintings are much more difficult to get to and seem to have been in a kind of holy of holies, which suggests that they have special status. In this shaft there are three animals: on one wall there is a rhinoceros on the left and a bison on the right. On the opposite wall is a horse. Beneath the tail of the rhinoceros is a cluster of six dots in two rows of three. The bison has been killed and his intestines are hanging out. Then between the two animals is a rather crudely drawn man, almost a stick figure. And we know that it is a man because the artist included a rather prominent penis. But the figure’s head appears to have a beak like a bird. There is a rather remarkable contrast between the artistic detail of the three animals with the crudeness with which the man is depicted. Beneath this man is a vertical stick with a simple outline of a bird that looks sort of like a cartoon duck perched on top.

So, what does this scene mean? Now when we’re dealing with the art of a civilization 17,000 years removed from us and where we have no other context, our interpretations are going to be highly speculative. It’s become something of a trope that when archaeologists come across some artifact whose purpose they don’t immediately understand, they just say that it must have been used in a religious ritual of some kind. Naturally most interpretations of the cave paintings of Lascaux assume that they had some kind of religious significance and were created and visited ritualistically to ensure good hunts. And I think it’s hard to deny that there must be something to that picture. But one elaboration of this kind of interpretation of the scene of the bird-man is that there is a celestial connection. Many cultures across the world have special figures in their society, generically termed “shamans,” who provide a kind of point of contact for the group between the material world and the spiritual realm, and across many cultures shamans are frequently associated with birds. This was true across many Native American groups and has been seen in archaeological artifacts as well, such as the Ust-Tartas site in Siberia, where a shaman was buried 5000 years ago wearing a headdress consisting of several dozen bird beaks. The association is intuitive — just as birds fly off to distant lands, so too does the shaman fly off to the spiritual realm. This would then suggest that the bird-man depicted in the painting is a shaman undergoing a trance. Now, when this painting was created, due to the precession of the equinoxes, the north celestial pole was quite a ways away from where it currently is today. The pole was right in the center of a bright asterism called the Summer Triangle, which consists of the stars Deneb, Altair, and Vega. Deneb and Altair are the brightest stars in the constellations Cygnus, the swan, and Aquila, the eagle, and both of these constellations fairly reasonably resemble birds. So the thought is that this painting may have depicted the heavens. The shaman has entered into the spiritual realm of the heavens. The vertical stick with the bird on top represents the pole of heaven about which the whole structure revolves. Then the three animals represent large constellations arrayed about the pole. The horse would correspond to the modern day constellation of Leo, the rhinoceros to the modern day Taurus, and the bison to the modern day Capricornus.

Well, some of you may find these interpretations intriguing, but it’s fair if others of a more skeptical bent don’t find them entirely convincing. So let’s turn now to another set of artifacts where the celestial connection is somewhat more solid. These are the megalithic structures that appear throughout Europe. These structures have been known to locals who lived around them down the centuries, they’re often hard to miss, but apart from some folktales around them, they were largely ignored. They only seriously began to be studied in the 19th century. By the early 20th century, the consensus opinion was that they must have been built in the 2nd millennium at the earliest. The idea was that it was known that civilization had developed in the Fertile Crescent sometime in the 4th millennium BC, and these structures were too technically sophisticated to have been built independently, so the local cultures had to wait for the cultural knowledge of how to construct megalithic structures to diffuse from the near east out to western Europe. It was only with the development of radiocarbon dating in the middle of the 20th century that it became clear that many of these structures predate the civilizations of the Mesopotamian by several millennia. These structures are associated with the transition from the Paleolithic Era to the Neolithic Era, when there was a large scale transition from a nomadic hunter-gatherer lifestyle to a more settled farming or herding lifestyle.

Now, there are some 30,000 megaliths throughout Europe alone, so I’ll have to limit myself to talking about a few of the more prominent examples along with some general characteristics that these structures share. Broadly speaking, there are three kinds of components in megaliths. The simplest of these is what is called a “menhir” and consists of a single standing stone. Now, while a stone just sitting there doesn’t seem all that impressive, many of these stones were quite large, weighing several tons and originated from many miles away. Transporting the stone and setting it upright required tremendous effort. And in many cases the stone was “dressed,” that is to say, it was smoothed, and some stones were even decorated with carvings. The second kind of component of a megalith is a “dolmen,” which consists of two stones or two rows of stones standing upright slightly apart from each other, and then a third stone, usually much larger, lying flat on top of them. The third component of megaliths is called a “henge” and consists of a ditch carved into the Earth, enclosed by a bank, and often with a ring of stones in the interior. A megalith may have just one or all three of these components.

Now, before getting into a couple of examples it’s worth dwelling a little bit on what kind of an astronomical connection we’re looking for in these structures. By and large, this connection has to do with the orientation of the structure. For instance, if the structure had some kind of axis that was exactly north-south or east-west, this would be strong evidence that the structure had some kind of astronomical significance. Now we today might see that and wonder what is really so astronomical about it. After all if you look at virtually any city in built in the last hundred years, the roads are almost always laid out on a north-south east-west grid. We don’t think of the urban planners of, say, Tulsa, Oklahoma as building their roads to manifest a connection between their city and to the cosmos. It’s just a convenient geographical layout — if you’re giving someone directions you can tell them to go three blocks north and then two blocks to the east. But this is a very modern way of thinking about it. After all, the notion that the cardinal directions, north-south, east-west are inherently geographic presupposes a heliocentric model of the universe, or at least one in which the Earth rotates on its axis. But prehistoric peoples had no such conception. The directions north and south had nothing in particular to do with the Earth. It was an exclusively astronomical association. North was the direction around which the stars rotated at night, east was the direction that the Sun rose in the morning, and west was the direction that it set. So if we see any alignments of megaliths along cardinal directions we have to understand that this represented an astronomical orientation. Now in practice we actually find that alignments along the east-west direction are relatively rare. Although the Sun rises generally in the east, it only rises precisely due east on two days of the year: the two equinoxes. But as we saw in our tour of Greek astronomy, measuring the dates of the equinoxes is relatively challenging compared to measuring the dates of the solstices. With the solstices you can simply mark where on the horizon the Sun rises or sets. The summer solstice occurs when this point is the furthest north. And, in practice, because the position doesn’t change too much for a few days around the solstice, you can figure it out when you notice that the Sun has stopped advancing northward. But unless you’ve already marked out what direction is east and west it’s hard to figure out when the equinox is with too much accuracy. And marking the east-west direction accurately is a difficult task on its own and would probably require a gnomon to trace the path of the Sun in the sky. So what we find in the megaliths is that orientations tend to be toward the point on the horizon where the Sun rose or set on the solstices rather than the equinoxes.

Now, if we’re trying to understand the astronomical connection of megaliths there are two ways we can go about it. One is on a case-by-case basis. If we see a structure with a precise alignment towards a direction of astronomical significance, like the position the Sun rises on a solstice or equinox, we can generally assume that there must have been some astronomical connection for this structure. The second way is statistical. If we collect many similar structures we may find that relatively few of them have a precise astronomical alignment. But in aggregate there may be a clear preference in orientation. There are, for instance, hundreds of similar dolmen structures in southern Spain and Brittany. Few are precisely oriented towards a solstice or equinox. But 185 out of 201 are aligned between east and south. The odds of this clustering occurring by chance are vanishingly small. And in several cases the exceptions seem to prove the rule. One structure called Dolmen de Menga in Andalusía is a passage tomb whose entrance is not oriented in this southeasterly direction. But if you stand in its corridor and look out you find that you are looking at a rather remarkable rock outcrop in the distance that bears the striking resemblance of a giant head lying on the ground and looking up at the sky. So in this case the builders seem to have chosen an unusual non-astronomical orientation due to the unique geological features of the area.

By the late Neolithic, around the time of the development of polished stone axes, say around 3000 BC, a new kind of megalithic structure starts to appear, particularly in western Britain, which are called stone circles, probably the most famous being the stone circle at Castlerigg. As you might infer, these are a collection of standing stones in a rough circle, usually around 30 meters across with around 30 stones. Incidentally, these circles are somewhat flattened which might initially seem to suggest that they were built a little haphazardly. But most of these stone circles are flattened in a similar kind of way, which suggests that the shaping was deliberate, though what the meaning of this shape was is unclear. In addition to the stones that form the circle, there are often two rows of stones attached to one part of the circle that form a sort of entrance corridor into the center of the circle. Generally these entrance corridors are roughly oriented towards the east. A lot of work has gone into studying the orientations of pairs of stones in the circle, drawing a sort of chord across the circle. In some structures like Castlerigg there does seem to be some intriguing alignments towards, for instance the position of sunrise on the cross-quarter days, that is, the days halfway between the solstice and equinox. And even more intriguing there are potential alignments with the position of certain moonrises, known as lunar standstills.

As I’ve mentioned before, the orbit of the Moon is inclined with respect to the ecliptic, so sometimes the Moon is further north of the ecliptic and other times further south. Once a month it reaches its northernmost position and then once a month it reaches its southernmost position, and these events are called lunar standstills. Due to the roughly 18 year precession of the lunar orbit the maximum or minimum declination of the Moon changes by about 10 degrees, and when this excursion reaches its maximum value it is called a major lunar standstill. At high latitudes like northern England and Scotland, the major lunar standstill can be quite an impressive affair. We’re all familiar with how surprisingly large the Moon can look when it is low on the horizon. At these high latitudes, when the Moon is at the southern portion of a major lunar standstill, the Moon rises very close to due south. This means that it travels in a low arc, skirting the horizon, making it appear extremely large the entire time it is up. So we tend to find stronger evidence for these kinds of lunar alignments in the megaliths of northern England, where the major lunar standstill would have been more visually impressive.

Well, we can’t talk about European megaliths without bringing up the one everyone knows and loves: Stonehenge. Stonehenge was built in an area that had long been inhabited, at least since 8000 BC. But it isn’t really a single structure, instead was built in three main phases. The first phase did not really bear much of a resemblance to what we think of when we imagine Stonehenge today. Around 4000 BC a henge was constructed, a ditch and an earthen bank, about 3 kilometers long and 100 meters wide and burial sites were placed nearby. Nearly 1000 years later a circular ditch was dug about 2 meters deep and 110 meters in diameter. The earth removed from the ditch was mounded to form a circular ring on the inner edge of the ditch. Then around the area are 56 pits about a meter in diameter which were used for cremation and burial.

About 500 years later the third phase of construction began and this is when stones get introduced and Stonehenge as we imagine it really started to take shape. Now, where the builders of the various megaliths across Europe got their materials varied. In the case of many dolmens, the builders probably built the structure around the large capstone so that the rock did not have to be transported anywhere, but just lifted vertically. But many other megaliths show evidence that their rocks were transported from miles away. But Stonehenge is really quite remarkable because during the initial stages of this third phase of construction, the culture responsible for building it transported 80 stones from about 150 miles away, each stone being about 2 meters tall and weighing about 4 or 5 tons. It was long thought that this task was far too monumental for a Neolithic civilization and that instead these stones must have been found much closer to the Stonehenge site, deposited there by glaciers at the end of the last Ice Age. But the main issue with this theory is that the builders would have had to have used absolutely every stone in the region for this structure because no isolated stones exist. Nevertheless, one of the principal mysteries of Stonehenge is just why the builders went to so much effort to obtain these particular stones and put them in this particular place, along with the more technical question of just how they managed to accomplish this feat.

These 80 stones were arranged in two concentric rings with an entrance on the north-eastern side, along with a pair of stones outside the entrance called Heel Stones. Then a few hundred years later a second set of 30 stones were moved into the inner circle and an additional 30 stones were balanced in a ring on top of the 30 standing stones. This is when Stonehenge took the iconic form you conjure in your mind when you imagine Stonehenge. The stones from this phase actually came from quite a bit closer, and were only transported from around 30 miles away. Within this innermost ring the builders arranged another set of stones in a horseshoe shape whose mouth faced the entrance to the complex. These are the largest stones in the entire structure, with the biggest being more than 7 meters in height. Presuming that Stonehenge served a religious function, this horseshoe would have acted as a kind of holy of holies.

Now Stonehenge has fascinated generations and has attracted wild theories about its significance to the Neolithic people who constructed it. As the archaeologist Jacquetta Hawkes put it, “Every age gets the Stonehenge it deserves—and desires.” There have been theories about how it was a sophisticated ancient observatory and that it computed lunar eclipses since the 56 holes in the outer ring would correspond to one quarter of a Saros cycle. But these kinds of ideas are at best speculative and in the wilder cases downright kooky. The main astronomical feature of Stonehenge is that the orientation of the entrance corridor and inner horseshoe is towards the solstices. If you are standing outside looking in, you would be looking in the direction of sunset on the winter solstice. In other words, in the depth of winter, you would observe the Sun seem to set into the heart of the structure itself. By symmetry if you are standing inside the structure looking out, this would be the direction of sunrise on the summer solstice. There is one other plausible astronomical feature of Stonehenge in the positioning of four unique stones around the outer ring, called Station Stones. These form a rectangle inscribed in the circle, and the direction of the longer axis of this rectangle is reasonably aligned with the direction of the major lunar standstill.

Well, there is a lesser known sister site to Stonehenge, named Woodhenge. Woodhenge is about 2 miles northeast and as its name implies it was made of wood rather than stone, so not too much remains of it today. But from the remains, there was an oval ring about 85 meters wide made of wooden posts in six concentric rings. These posts would have been no joke, based on the holes they sat in, archaeologists estimate that they would have been some 8 meters tall and weighed a few tons. Woodhenge is aligned along the same axis as Stonehenge, but in the opposite direction. So if you were standing outside the structure looking in, you would see the sunrise on the summer solstice seem to come out of the structure. Stonehenge and Woodhenge also differ in the fossil remains present. There is a large quantity of butchered pig bones around Woodhenge, which suggests that great feasts which took place there, but Stonehenge instead contains human bones. The picture that emerges is that these two structures complemented each other, with Woodhenge being a place of the living and Stonehenge being a place of the dead. This is reflected in the orientation of Woodhenge towards sunrise on the summer solstice which would be suggestive of the flowering of life, whereas the orientation of Stonehenge towards sunset on the winter solstice would have been associated with death. What’s more, we see this association in the materials that each structure used, inanimate stone for Stonehenge and a living material for Woodhenge. And in fact this kind of association is not unique to the Neolithic, there are groups in Madagascar, for instance, that continue to build megalithic structures right down to this day, and they have the same association of wood with the living and stone with the dead.

Another of the most impressive European megaliths is a complex of three structures built around 3200 BC along the Bru na Boinne river in eastern Ireland, called Newgrange, Knowth, and Dowth. Each of these structures is a large burial mound around 90 meters wide with a kind of stone wall around the edge. Newgrange has a stone passage that leads you into a somewhat larger central chamber, whereas Dowth and Knowth both have two such passages. The structures appear to have been built inside out, with the inner chamber being constructed first, then the stone passageway, and the earth being piled on top of it all afterwards. One piece of evidence for this is that inside one of the chambers at Knowth there is a large stone that might have acted as a kind of altar or religious artifact. Or at least, there used to be such a stone inside the chamber. At some point over the centuries some group of people tried to steal it. They started to drag it out of the passageway but discovered midway through that the passage narrows and the stone actually cannot fit through the passage and get out so they abandoned it there.

Like other megaliths of this kind, Newgrange, Knowth, and Dowth were tombs and contain burnt and unburned human remains. But it seems that not just anyone was buried in one of these structures. DNA from one of the individuals indicates that his parents were probably brother and sister. This kind of extreme incest generally only occurs in royal families where it is important to preserve a bloodline, so this implies that burial in these grand megaliths was reserved for a small number of important people in a community.

As with Stonehenge, the main astronomical feature is the alignment of these passages with the solstices, the winter solstice in particular. For a long time, however, there was a mystery about the nature of this alignment. The passages are indeed oriented towards the winter solstice, but the passage is sloped downwards underground. Due to this downward curve you cannot actually see the sunrise inside of the central chamber. Nevertheless, folktales from the Irish locals indicated that there was a strong connection between the monument and the solstice. During its excavation in the 1960s, the archaeologist Michael O’Kelly discovered a smaller opening above the entrance to the passage, called the “roof box.” It originally appeared to have some moveable slabs so that it could be opened and closed. When it was opened, O’Kelly discovered that on the winter solstice, it allowed the light from the sun to pass all the way into the central chamber.

These structures contain some of the most remarkable examples of Neolithic art. The stones that ring them and line the passages are decorated with a panoply of abstract shapes, spirals, circles, dots, and squiggles. During the 60s and 70s, some archaeologists did a little bit of, shall we say, extracurricular research and noticed that the shapes on these megaliths are rather psychedelic and resemble the patterns that one hallucinates during an acid trip and so they suggested that perhaps these shapes were inspired by the patterns that shamans saw during their hallucinogenic trances.

But one of the most intriguing set of inscriptions is at Knowth where there is a stone with a set of 29 crescents and circles. Now, anytime you hear the number 29 your spidey-sense should immediately tingle since this isn’t a random number, it’s the number of days in a synodic month, the time from full moon to full moon. So this set of crescents and circles may have been one of the earliest lunar calendars.

Incidentally this is not the only potential lunar calendar on a megalith. There is also a passage tomb in Brittany called “Gavr’inis.”Like many other megaliths, the passage is oriented towards the direction of the winter solstice, but unlike many other megaliths, the tomb is lavishly decorated. There are 29 stones along the sides of the passage and the slabs are decorated with what appear to be shepherd’s crooks, with 29 of these symbols on the left side and 27 on the right. Once again your spidey-sense should tingle. 29 is the number of days in the synodic month and 27 is the number of days in the sidereal month. More speculatively, there are also 19 other curved snake-like symbols and 19 is the number of years in a Metonic cycle.

Incidentally, one of the interesting features that Gavr’inis shares with Newgrange is that many of the stones appear to have been reused. Some of the slabs have decorations that were facing away from the passage into the Earth, so that they were hidden from view, and these decorations appear to be broken off partway through. The carvings on one of the slabs can be matched up with another broken slab in a separate megalith a few miles away. What probably happened here is that the builders of Gavr’inis scavenged the material of an older nearby megalith, but were careful to hide away prior carvings so that they would not mar the aesthetics of the new work. Gavr’inis is not the only example of Neolithic builders scavenging material from earlier megaliths. There is an extremely large stone originating from Locmariaquer in Brittany which was the largest known, originally over 20 meters tall and weighing about 330 tons. Originally the stone was decorated with geometric patterns. But at some point the rock was broken up into four pieces, probably deliberately. These pieces were then transported a few miles to several separate sites. The original decorations were turned inwards to hide them from view and new decorations were carved onto the other side. Evidently these structure was constructed prior to the formation of historical preservation societies.

The last megalith I’ll mention is further south and is actually a set of megaliths on the island of Menorca, one of the islands of the Balearic Islands in the Mediterranean near Spain. As I mentioned towards the beginning, the early theories of the development of megaliths were that these structures originated in the Fertile Crescent, or maybe Egypt or India, and then spread west to Europe. But the megaliths of the Mediterranean come much later than the megaliths of the British Isles and Western Europe. Around 1000 BC hundreds of megaliths were were constructed on the island, including dozens of structures which are called “taulas.” These are stylistically quite different from the megaliths seen on the continent and in the British Isles. They consist of a sort of oval or rectangular column with a rectangular stone lain on top. The taulas are almost all oriented to face south, which indicates that they had a clear astronomical connection. What the precise connection was is unknown, but one intriguing theory is that around the time they were constructed, at this latitude the stars Alpha and Beta Centauri and the stars of the southern cross were just becoming visible due to the precession of the equinoxes. These stars are all very bright, Alpha Centauri is the third brightest star in the night sky, and they form a fairly compact and eye-catching cluster. The people of Menorca may have noticed the emergence of this new cluster of bright stars appearing low on the southern horizon and oriented their megaliths towards these new stars.

But again, as with all these Neolithic cultures, all we can say for certain is that they must have constructed these megaliths with an eye towards the heavens because the orientations are much too frequent and much too precise to have been due to chance. But trying to interpret the meaning behind these orientations is a highly speculative enterprise with the archaeological evidence we have available.

Well, with that we will leave Europe behind us for some time and next month turn to the astronomy of sub-Saharan Africa. I hope you’ll join me then. Until the next full moon, good night, and clear skies.

Additional references

  • Brennan, The Stars and the Stones
  • Belmonte, Ancient Astronomy
  • Kelley, Exploring Ancient Skies
  • Magli, Archaeoastronomy
  • Frank, “Hunting the European Sky Bears”