Each of us tells a story about who we are, often tracing our identity back through an imagined line of ancestors. Though identity is fundamentally cultural, we tend to anchor it in biology – in the idea of a stable genetic inheritance passed down through generations.

Population genomics has exposed a history far more complex, dynamic and intertwined than we might wish to imagine. Even in a place such as Britain, long imagined as an island of deep and uninterrupted heritage, genetic data suggest a history marked by intense migration, mixture and cultural reinvention.

Two new studies have reinforced this picture, by analysing DNA from the skeletal remains of British individuals who lived during Roman and medieval times.

Prehistoric Britain witnessed periodic major migrations interspersed with smaller and more regular movements of peoples across what was then a contiguous landscape.

After about 6100BC, rising sea levels isolated Britain from mainland Europe, helping to promote later historical narratives of a population relatively isolated.

Yet even early observers recognised otherwise. Writing in the first century AD, the Roman historian Tacitus noted the diversity of Britain’s tribes, suggesting their origins lay in Germany, Gaul and Iberia.

Such conclusions were drawn from physical, cultural and linguistic observations. Now it is testable, thanks to rapid advances in population genomics and ancient DNA sequencing, allowing direct ancestry reconstruction across demographic and political changes.

A major recent study by Marina Silva, from the Francis Crick Institute in London, and colleagues analysed more than 1,000 ancient genomes from across Britain during the first millennium AD.

The pre-print, which has not yet been published in a journal, asks one simple question: could the main historical events of Britain – the Roman occupation, Anglo-Saxon migration, the Viking Age and the Norman conquest – be detected in the genetic data of the populations that lived through these eras?

The answer was complicated. The Roman period, for all its political and cultural upheaval, left surprisingly little mark on the genetic structure of the wider population. About 80% of the individuals who lived during Roman times in Britain cluster almost exactly with those of the immediately preceding Iron Age, arguing for genetic continuity and no replacement. Even in urban centres where occupying Roman elites were most prevalent, the broader population retained overwhelmingly local ancestry.

In contrast, the early medieval period, from around 410AD (when Roman rule collapsed) to 1066AD, saw a substantial influx of new ancestry from across the North Sea. The researchers were able to detect this influx by comparing the British samples with genetic data from populations in other parts of north-west Europe. Continental ancestry associated with Anglo-Saxon migration appears in more than 70% of of the burials in southern “Anglo-Saxon” Britain.

Thus, migration was not just cultural but demographic on a scale sufficient to leave its imprint on the shape of population structure.

Yet even this transformation cannot be generalised. From about 700AD to 1000AD, further waves of continental influence appear in Britain, with the arrival of settlers from central Europe (seemingly from France and the Rhineland) and, to a lesser extent, the south of Europe. However, the Viking Age leaves a more uneven and regionally variable genetic signal than its historical prominence might suggest.

While a Scandinavian component is clearly present in northern and eastern regions, it is rarely of a magnitude comparable to that found in early medieval migrations. Most surprisingly, the Norman conquest of 1066 appears to have been largely an elite process, leaving little detectable trace in the genomes of the common population.

Genome-wide ancestry profiles straddle the date of the conquest, with no hint of abrupt population replacement. Despite all its drama, the conquest seems, at the level of population genetics, to have involved elite replacement by relatively few individuals.

A second pre-print study provides a closer view of what this looked like on the ground. Focusing on a rural cemetery at Priory Orchard in Surrey, Flavio De Angelis, from Arizona State University in Tempe, and colleagues examined individuals buried across the centuries before and after the Norman conquest.

Again, the results are surprising: rather than any clear genetic break after 1066, both pre- and post-conquest burials fall within the same cluster, showing shared ancestry and no evidence for demographic turnover. The continuity is not just qualitative, but visible in the statistical similarity of ancestry components across generations.

Instead, the community reflects a much longer history of interaction across the North Sea world. Its ancestry includes Anglo-Saxon-associated components, significant Scandinavian input dating to the Viking period, and smaller continental contributions.

Crucially, these elements are already present before the Norman arrival and persist afterward. The Norman conquest, in genetic terms, is barely visible. What looks, on historical timelines, like a moment of dramatic rupture appears, at the level of the common individual, as a continuation. Genes tell the story of populations and detect localised impacts of migration, but they do not map neatly onto geopolitics.

Taken together, these studies point to a crucial distinction. Cultural and political change does not necessarily equate to demographic change. Britain’s history is neither one of uninterrupted continuity nor of repeated population replacement, but something more complex: long-term mixture punctuated by events that reshape institutions more than populations.

Some migrations – such as those of the early medieval period – left deep and measurable genetic legacies. Others, despite their prominence in historical narratives, left only faint traces. The discrepancy is striking: the scale of genetic change does not map neatly onto the scale of historical attention.

Modern genetic data reinforce this picture. Contemporary populations across the British Isles do not form a single, uniform group. Instead, they cluster into overlapping but distinct lineages reflecting different regional histories and varying degrees of past migration.

These patterns echo the ancient record, but they did not affect all regions equally. Wales and Ireland retain stronger continuity with earlier populations, while England shows clearer evidence of ancestry linked to early medieval migration from northern Europe. Scotland occupies an intermediate position, reflecting both long-term continuity and later Scandinavian influence.

Importantly, these differences are matters of degree, not kind. All populations of the British Isles share deep common ancestry overlaid by layers of migration whose effects vary regionally. The structure we see today is the product of these layered histories, not the survival of isolated or “pure” populations.

What emerges is not a story of rooted, bounded identities, but of continual connection. British identity – like all identities – has been assembled over millennia through movement, interaction and adaptation.

Modern genomes do not simply tell us who we are; they preserve how we got here. History does not make migration exceptional – it reveals it as the norm.

Jay Silverstein does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

There is not yet much research on the effects of heatwaves on bees. What little there is focuses on super extremes of weather that would kill an adult bee.

However, my new research with colleagues shows that UK populations of solitary bees may be much more sensitive than previously thought to the kinds of extreme weather we are now seeing regularly.

To find out what happens to bees during hot weather, my team recreated the three-day UK heatwave of July 2022. We subjected a group of developing larvae of red mason bees to three days where temperatures peaked daily at 40°C.

Red mason bees are common solitary bees found in UK gardens, and are important pollinators of apples and other fruits. At the same time, a control group experienced normal July temperatures for Hull, where the study was conducted, peaking daily at about 25°C.

After that, we treated both groups identically and allowed them to spin their cocoons and hibernate as normal. Nine months later, all the bees emerged fine, so it appeared initially that the heatwave had had no effect.

But this was before we dissected the bees to look at their reproductive health.

Staggeringly, in males from the heatwave group, sperm activity had dropped by half compared with the control group, and sperm counts by one third. In females, there was a 15% reduction in both the size and the number of developing eggs.

The heatwave had wrecked their fertility, especially in males.

Reduction of sperm motility in bees during heatwave

These numbers are shocking because they suggest solitary bee populations are much more sensitive to weather extremes than we thought, and that this should be factored into calculations of the broader effects of climate change. While bees did not die outright, their fertility was severely affected.

This means that a heatwave one year could lead to a drastic drop in the number of bees the following year, and therefore less efficient pollination for key crops like apples, cherries and oilseed rape.

This would leave commercial fruit growers even more reliant on temporarily renting honeybee hives, commonly called “hire-a-hive” schemes, to combat pollination deficits. This is at a time when research increasingly shows that wild bees, whose services come for free, are better pollinators than honeybees.

What else happens in heatwaves?

In honeybees and bumblebees, living together as a group is the key to withstanding weather extremes. With their social hives, honeybees can flexibly respond to periods of heavy rainfall and strong winds by rapidly reallocating the tasks that worker bees perform – switching from nest maintenance to foraging, for example.

Honeybees and bumblebees are also able to respond to temperature changes. They maintain their nests within strict temperature limits, with some workers switching to becoming living radiators when temperatures drop, buzzing their wing muscles to produce heat that keeps the brood at the ideal growing temperature.

Bumblebee nests begin with a single queen hibernating over winter and then working alone to build up her brood. New research is revealing secrets of their resilience: for example, hibernating bumblebee queens can survive underwater for up to a week when their nest is flooded.

However, honeybees and bumblebees are not most bees.

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Read more: Queen bumblebees can breathe underwater — for days. We discovered how

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Unlike honeybees and bumblebees, most bees are solitary, which means they don’t have social nestmates to help them when times get tough – they work entirely on their own. Nests of these solitary bees are at the mercy of the elements, so solitary bees are much more vulnerable to climate change than social bees.

Of course, heatwaves are not the only threats to bees. They have an array of other nightmares to cope with, including pesticides, diseases, nutritional stress and loss of habitat.

The priority now is to investigate how bees affected by heatwaves also cope with these other problems. Our lab heads up a government-funded study looking at how climate change affects the nutritional needs of growing wild bees, and how parent bees respond to these needs.

Excitingly, we are beginning to see patterns indicating that growing bees require different balances of nutrients when they are reared at different temperatures. We are now testing whether bee mothers are sensitive to these requirements, and can adjust the pollen they gather to compensate.

Extreme hot weather is becoming more prevalent, even in cooler countries. These studies show that severe weather, while not necessarily killing bees outright, has the ability to seriously damage the bee population – with long-term consequences for pollination as well as the human food chain.

James Gilbert currently receives funding from UKRI (BBSRC) and the study mentioned in this article, on which James is a coauthor, was funded by UKRI (NERC).