I have just come back from a short time away in and around Lindisfarne, in the north-east of England not far from the Scottish border. Its other name is Holy Island, reflecting the fact that for a great many years – from its foundation as a monastery around 634 to the 16th century – it was best known as a centre for prayer, worship, and learning.

Lindisfarne is one of those places which is an island at high tide, and connected to the rest of Northumberland by vast mud flats at low tide. Twice a day the sea comes in and gathers the island into itself, and twice a day the sea withdraws again and allows traffic to pass freely. It’s a most magnificent symbol of the way the human psyche engages with and separates from the world. We have times of busyness, and times of withdrawal. Even if it’s only in sleep, all of us have this tidal cycle running deep in us, and it goes far beyond rest and recuperation.

This part of Northumberland also has a huge variety of wildlife – flowers, birds, and insects are everywhere. The birds are at their most striking during the spring and autumn migrations, but there are plenty around in the summer as well. And the Lindisfarne seals sing! Perhaps seals in other places do this too, but I have never heard them. But on a rising tide, as the mudbanks where they are hauled out in their hundreds gradually shrink, you can often hear their song, somewhere between a wolf pack howling and the wind sighing, and not quite like either. There’s plenty of wind on the island as well, but when you hear that song, you have no doubt you are listening to something that a living creature has produced.

No wonder that the founding monks of the Lindisfarne community – Aidan, Cuthbert and all – chose this place to build something which joins both this world and the other. We know comparatively little about occupation of the site before their time, but I’d be confident that it was recognised as a liminal place long before the arrival of Christianity here.

Augustine of Hippo, speaking out of his own religious heritage, wrote that “our souls are restless, until they find their rest in Thee“, and you’d be hard-pressed to find a better place to find both restlessness and rest than here.

Times have changed a little – the monasteries have been disbanded, the habitual practice of Christianity has changed in many ways, and the island is now connected to the mainland in more sophisticated ways than a footpath. But when you’re on the island, the feeling of being away from the mainland presses closely around you. Spirituality remains a major influence on the life of the island, and people still visit for the purpose of feeding their souls. And the cycle of tides still separates this little place from the mainland twice a day.

Throughout most of human history, we have made great efforts to commemorate the dead, particularly those who were important in some way, or whose actions deserved special honour. Conversely, we have shown disapproval by denying proper burial, or defacing graves and monuments. In ancient Egypt, a person’s name might be obliterated, with the intention of depriving them of both recognition and tangible offerings by future generations. But it is our treatment of the honoured dead which interests me today.

We have often buried a body, but we have also often buried the burned ashes of bodies, or items they used in life. In these cases, the tomb serves as a formal reminder of the person rather than an actual resting place. We have buried people singly, but more often in groups, according to family ties or the roles they fulfilled. And very often we have raised our memorials to the dead in prominent places, as an ongoing sign to the living.

Through most of history, until comparatively recently, we have liked to keep our dead close to us. Looking back in time, it is hard to know what the reasons for this were. Could it have been protection, to ensure that malevolent influences were kept at bay? Or to placate ancestors who might judge the living harshly? Or to provide comfort in a time of mourning? Or simply for convenience, to simplify the process of providing both prayerful respect and tangible offerings? Today, even though we are often geographically scattered from our ancestors, the sight of a grave that has been cared for and adorned with fresh flowers – or more personal items – usually touches and inspires us. Perhaps we see it as a vicarious offering on our own behalf, when we cannot do the same ourselves.

On the Scilly Isles in the late Neolithic and Bronze Ages, the honoured dead were remembered with large stone cairns. They are now called entrance graves, and the style is largely unknown in most of Europe. A central area, roughly the size of a coffin, was lined with stones on either side. One end was chosen as the entrance, and blocked with a separate stone, often slightly offset so as to leave a gap. Finally, several large capstones were placed on top – this itself must have been a serious undertaking given the weight involved. There is a natural orientation to the graves – the line through the middle pointing in or out of the door – but there is no overall consistency about this orientation.

Few if any of them seem ever to have contained dead bodies, or even extensive grave goods, though ashes and oil have been found in some. Presumably the monument itself was sufficient to commemorate the people involved, even over several generations.

On Scilly we find these monuments on the tops of hills, clustered together in lines and groups. That in itself is not very surprising, since it made them easily visible. But on Scilly, these hills are situated in a ring on the seaward edge of the land – the central lower-lying plain is now submerged under the encroaching Atlantic. This has happened within historical memory, and accounts from the Roman era through until the time of the Norman kings tell us of the gradual division into the archipelago we now see.

So this raises again the question of motive. Did the builders of these tombs expect that the honoured dead would protect them from invaders from over the sea? Perhaps even from the sea itself, since I am sure that the communities of the time would be aware that ancestral lands were, little by little, being eaten away. Or was the intention to face outwards, so that a person’s tomb remembered a great voyage they had made, or fishing areas that were especially generous?

At this remove in time, given that we are dealing with a culture that either could not or chose not to record itself in writing, we cannot answer these questions. They remain as enigmatic as the stones themselves. What we do know is that these places remained important to Scillonians for a very long time. One burial – Bant’s Carn, on St Mary’s, remained intact throughout the Bronze and Iron Ages, despite the presence of Halangy village which thrived just down the hill from it for many centuries. The villagers may have continued to hold ceremonies around the tomb, or may have placidly ignored it, but they lived in its shadow and took care not to demolish it. The desire to honour the dead runs very deep in us.

Today is another look at prehistoric monuments in England, and in particular the way sites were reused and reinterpreted by later generations. My main focus is going to be religious or sacred use – obviously some houses and forts stay in use for many hundreds of years, but this doesn’t usually involve much change of purpose.

The modern stereotype is that later religious groups are implacably hostile towards earlier ones, violently trying to erase all signs that things were ever different. Certainly this happens from time to time – the attempted destruction of Palmyra is a glaring recent example – but actually, quiet assimilation of a site is very common.

Let’s look first at Stonehenge. Before the raising of the giant stones which are most people’s association with the site, there was a true henge there. The earliest part of the whole structure is a circular bank with an entrance facing compass point. There was also a ring of wooden posts, including a series set at intervals across the entrance, and a few outlying marker stones picking out specific angles from the centre.

Now, like most henges of its era, it was built around lunar alignments. The centre of the entrance, the postholes across it, items buried at particular places in the ring – even the main outlying stone called the Heel Stone – all of these pick out significant events in the lunar cycle. Now, since a full cycle takes 18.6 years, and it would take a few such cycles to be sure of the observations given inconveniences such as clouds, this already represents a huge summary of embodied knowledge. But let’s move on.

Time passed, as did the original builders, and the site was reused by new people with new beliefs. They didn’t just put up new stuff – like the stones – they repurposed the whole place. The entrance was widened, but asymmetrically, so that the midpoint was now angled to accommodate a solar orientation. You have to wonder if the newcomers were aware of the previous lunar settings and making deliberate changes, or if they just thought the earlier inhabitants had built it wrong. Even in very recent years, we’ve certainly not understood the builders’ purpose.

Whatever the level of knowledge and the motives of the new users, the end result was to rebrand Stonehenge as a solar monument. The great majority of visitors since then have seen only this more recent, more obvious configuration, and the rediscovery of the older focus on the moon has been slow to emerge.

We know nothing about the transition from lunar to solar beliefs. Was it a peaceful and gradual shift, or a sudden and more violent one? Did the circle remain in regular use throughout, or was it abandoned for a while? It seems to me that the fact that the same site was reused, whether after a gap or not, must say something. It would be all too easy for the new solar-oriented worshippers to simply ignore the very obvious bank of earth and wooden posts, and erect their own monument nearby. Yet they chose to carry on in the same place.

Such reuse of an older sacred place by later generations is very common. Many springs and pools held sacred to the traditional religions of the British Isles were adopted by the Romans, Saxons and Normans, often ending up linked with Christian saints and having churches built there. Knowlton church, in Dorset, was situated within the ring of a much older henge, and most of Avebury village is inside the huge extent of the monuments there. In Karnak, part of the Pharaonic temple was used as a Christian church, and subsequently a mosque.

What motivates this reuse? Does it represent a kind of spiritual conquest, in which the new element needs to purify the old? Or is it a way to legitimise the new by means of linking it with a place long held to be sacred? Is it simply that people are already used to going there, and this is a way to set up your pitch where there are already crowds of worshippers? Or is it that some places on earth really do have a heavier weight of sacredness than others, and some sensitivity to this motivates the builders of places of worship?

For the monuments I am thinking of, we will never have historical records which might explain the motives. All we have are enigmatic questions, and the clear signs that religious sites changed their focus over the generations as the original purpose became less important.

Looking forward in time, I wonder what might happen if we encounter signs that alien races have built sacred monuments elsewhere in our solar system or further afield? Will we set up our own shrines among the stones and stellar alignments, and in doing so continue our millennia-old habit of reuse? Right now we have no clear signs of extraterrestrial life of any kind at all, still less life that is sophisticated enough to reflect on the universe and build artefacts in holy places. One day, perhaps.

Our quest for companionship goes back a long way. According to the Hebrew Bible, it arose during the time of creation, when God brought all the animals and birds to the man – “the human” would be an appropriate translation. The reason was “it is not good for the human to be alone” Then “the human proclaimed names for all the domesticated animals and for the birds of the skies and for all the living things of the open country“. Sadly, amongst all of this array of life, no suitable helper could be found. So God went on to make a suitable helper.

My point today is nothing to do with how best to understand the creation story in Genesis, but to show that this tradition – along with many others all around the world – presents the idea that mankind has wanted to find companionship of some kind with the natural world for a very long time. We use the natural world all the time in our descriptions, similes, and metaphors about human behaviour, and although there are some mismatches when we try to carry such metaphors cross-culturally, by and large they survive translation very well.

The Biblical tradition became, through the course of time, increasingly antipathetic to representing the godhead in terms of animals, but animal metaphors remain strong throughout – eagle, bull, lamb, and so on. In other traditions, where the constraints against idolatry were weaker or absent, living things have been fair game to stand in for gods, demigods, spirit guides, familiar spirits, and so on. The Egyptian tendency to associate animal features with otherwise humanoid deities intrigued (and rather horrified) Europeans. But the Egyptians are very far from the only culture to do this. Classical Greek literature is full of transformations into and from animals, birds, plants, and so on. Hindu sacred texts associate one or more vahanas with each deity. These were – are – devoted companions, often used for riding, and typically taking animal or bird form – bull, elephant, peacock, mouse, tiger, owl, and so on.

Personally I’m not so bothered about a literal interpretation of all this, but I am very interested in what it might carry in terms of meaning. There’s an obvious connection in terms of linking the qualities of the beast with the god in question. So Sekhmet – with her lion head – was thought to protect the line of pharaohs and lead them in battle. But on another level, followers are encouraged to meditate on the imagery, and to use the real-world object as a vehicle to approach the godhead. Modern neuroscience thinks in terms of an animal brain, and a reptilian brain, and so on, biologically nestled within our human brain, and tending to pop to the surface and dominate our reactions from time to time.

Another modern symptom of the same trend is the quest for animal intelligence. We have found signs of this in dogs, pigs, most of the apes and upper primates, corvids, parrots, dolphins and whales, and so on. The early 19th century saw great interest in Learned or Sapient pigs, able to accomplish a wide variety of tasks… or where they just tricks? Since then we have expanded the study to a whole bevy of other living things, and in the process come to realise that we don’t really understand human intelligence! Which part of the brain is responsible for it? Or is it a generalised response emerging somehow out of the whole organism?

So we are still looking for companionship here on Earth, whether spiritual or intellectual. Arguably the quest for discovering alien life out in the rest of the cosmos is part of this great search. If it really is “not good for the human to be alone” then the quest will no doubt continue for a long time to come… in parallel with the quest to find companionship in the humans alongside us.