Astronauts who undergo long-duration spaceflight aboard the International Space Station often return with health problems that resemble some age-related conditions in people on Earth.

Remarkably, some of this decline reverses within months of their return but others persist. This raises an intriguing question: what can be learned from these rapid changes and could they help prevent or reverse aspects of age-related decline on Earth?

That question has turned space into a laboratory for ageing research. Spaceflight reproduces many features of ageing. Astronauts also experience unusual conditions, including very low gravity, increased radiation and disrupted sleep. Even so, changes that usually develop over decades on Earth can appear within weeks or months in space, giving scientists an opportunity to observe some ageing-related processes in fast-forward.

A 2026 study, which tracked four astronauts during the nine-day Axiom-2 mission, examined chemical markers attached to DNA that can be used to estimate biological age. This is an estimate of how old the body appears to be based on molecular changes, rather than the number of years a person has lived.

The astronauts’ estimated biological age increased during the mission and began to fall after they returned to Earth. This does not mean that they physically aged by years in a matter of days. With only four participants, the study cannot provide firm conclusions, but it shows how rapidly the body can respond to the conditions of spaceflight.

Why would leaving gravity behind affect the body in ways that resemble ageing? On Earth, muscles, bones, and the cardiovascular system and other organs are adapted to function under the constant pull of gravity. That continual mechanical load helps keep these systems healthy, although their function often declines later in life. In space, many of those demands disappear.

When muscles age in fast-forward

Skeletal muscle provides one of the clearest examples. Astronauts lose muscle mass and strength at a startling rate in very low gravity, even while exercising for around two hours a day to attempt to limit the effects.

Some of the biological processes involved may overlap with those associated with sarcopenia, the age-related loss of muscle strength and mass that increases the risk of frailty, falls and loss of independence.

Scientists are still working out how closely muscle loss in space resembles sarcopenia, because similar effects can arise through different biological processes. The crucial difference is timescale. That compression is exactly what drew our team to space.

Through our UK Space Agency-funded MicroAge mission, we sent lab-grown human muscle constructs to the International Space Station.

These miniature muscles, roughly the size of a grain of rice, were engineered from human muscle stem cells. Using lab-grown tissue, rather than relying solely on the limited number of astronauts available for study, allowed us to compare muscle adaptations in very low gravity with those seen during ageing on Earth. It also allowed us to carry out early tests of possible ways to protect muscle. If some of the same mechanisms are involved in both settings, space could provide a useful opportunity to study years of biological change over the course of months for a single mission.

Our follow-up mission, MicroAge II, will explore the biology of this decline in greater detail. It focuses on mitochondria, the structures inside cells that produce most of the energy those cells need. Problems with mitochondria are recognised as one process involved in muscle ageing on Earth.

MicroAge II will investigate whether similar changes to their structure and function also contribute to rapid muscle loss in space. Why does any of this have significance beyond the space station?

Loss of muscle mass and function is one of the most consequential aspects of growing older. It underlies frailty, falls and the loss of independence that many people fear, yet effective treatments remain limited. Testing potential interventions in populations that age over decades is inevitably slow. Space research will hopefully help scientists identify relevant biological processes and test early ideas more rapidly.

Experiments in space cannot replace final clinical studies involving older people, however. Any treatment suggested by this work would still require extensive testing on Earth to establish whether it is safe and effective but would identify potential drug candidates far more quickly.

Samantha Jones receives funding from UK Space Agency.

Anne McArdle currently receives research funding from the Medical Research Council, the Biotechnology and Biological Sciences Research Council and UK Space Agency.

The ability to cross oceans has long been a marker of human endeavour, but when did the seas change from being barriers to movement into the maritime highways we know today?

For many years the answer was thought to lie in the Neolithic period – the time when humans made the profound transition from hunting and gathering to practising agriculture and living in settled societies.

Our team’s discovery of the presence of European hunter-gatherers on the tiny Mediterranean island of Malta, reported last year, has overturned this view. It showed that people reached Malta from their starting point in Europe (presumably Sicily) at least 8,500 years ago.

In a new study, we show that these populations were engaging in repeated long-distance sea journeys of at least 100km, well before the advent of farming.

Researchers have known that the occasional very ancient sea crossing must have been made. The most famous example may be the colonisation of Australia, tens of thousands of years before the present.

However, sustained, long distance sea voyaging – particularly to small and remote islands – was long thought to have been beyond the capabilities of hunter-gatherers, who are dependant on the bounty, or deprivation, of natural resources.

This was also the case for Europe’s last hunter-gatherers, in the period of time known as the Mesolithic, the era before the Neolithic. During the Neolithic, a new population introduced agriculture to Europe from Anatolia (which comprises most of the landmass of modern Turkey).

Enter the recent findings from the site of Latnija, on Malta. Did the surprising presence of European hunter-gatherers on Malta reflect a one off, accidental crossing – or perhaps people who somehow became marooned on the island? Conversely, was this Mesolithic presence a reflection of something altogether different, and more complex?

Shifting seas

To explore these possibilities, we investigated whether Malta could support a viable forager population size that could have lived in isolation for the 1,000 year occupation of the island during the Mesolithic.

First, we explored the impacts of changing sea levels since the Last Glacial Maximum (the height of the last ice age), from around 21,000 years ago. This was when waters began to rise from their lowest levels of around 130m below modern sea level. By doing this, we were able to track changes in the size of Malta and its connectivity with surrounding islands and land masses.

During the Last Glacial Maximum, Malta was connected to Sicily by a land bridge, and this connection remained as sea levels continued to rise until around 14,000 years ago, when the land bridge began to be inundated. Continued sea level rise meant that within less than a thousand years, Malta had become far smaller and remote from Sicily, needing a long-distance sea crossing for connectivity.

By the time of the Mesolithic occupation, Malta had almost reached its present configuration, with no significant difference in distances to Sicily. Having understood how sea level rise impacted the size and accessibility of Malta, we next explored how its specific ecological conditions impacted its ability to support forager populations. Since hunter-gatherers are reliant on what nature provides, their population sizes have a direct relationship with ecological productivity.

Accordingly, we modelled the relationship between population density among contemporary forager populations and what’s known as net primary productivity – effectively the baseline of wild resources available to hunter-gatherers. We then extrapolated these findings back into the past using high resolution computer models of past climates (palaeoclimate models).

This enabled us to calculate the total population size that could be supported first on the combined landmass of Malta and Sicily, and then as separate islands as sea levels rose.

Our upper estimates for the total population sizes suggest that after the inundation of the land bridge to Sicily, the total population size that could be theoretically supported on Malta dropped rapidly to 319 people by 13,800 years ago.

There is no evidence yet that people were living on Malta this early, but our models showed that any populations present would have continued to drop in size as sea levels rose until around 9,000 years ago, when it could have accommodated around 170-144 people.

Finally, we compared these findings to thresholds, informed by conservation genetic studies, for the long-term viability and stability of a population. These thresholds suggest the need for an effective (reproducing) population size of 1,000 or more, equivalent to a total population size of 2,500-3,000 (because the total population size includes both younger and older people who are not reproducing).

Long distance voyages

This suggests that Malta was incapable of hosting an isolated, viable population that could have lived continuously through the 1,000-year time frame during which it was settled by Mesolithic hunter-gatherers.

Consequently, we can rule out the persistence of a population stranded on Malta as sea levels inundated the land bridge to Sicily. We can also exclude a single, perhaps unintended, voyage leaving marooned mariners on Malta.

The only alternative is that these Mesolithic hunter-gatherers were making repeated, long distance sea voyages between at least Malta and Sicily, the closest land mass, to maintain the genetic connections that ensured at least a millennium of Mesolithic viability on Malta.

These insights are reshaping our perceptions of late European hunter-gatherers and the sophistication of their societies. To maintain repeated, long-distance overseas connections, they must have had, and conserved, an extensive knowledge of land, sea and sky, as well as the technological know-how for building and preserving sea craft.

We don’t know for certain what type of vessels the hunter-gatherers were using, although we know that dug-out canoes existed at this time. The crossings to Malta occurred several thousand years before the earliest evidence for sails – making the achievement even more impressive.

From wayfinding to getting food at sea overnight, they then had to be able to live sustainably on a small, semi-arid island, which required a finely-tuned knowledge of diverse food sources shaped by the seasons.

With these implicit capabilities, we can then start to ask, where else did they go? There is already evidence of connectivity between Europe and North Africa during this time. Previous work using ancient DNA found the distinctive signature of European hunter-gatherer ancestry in people living in pre-Neolithic Tunisia.

All this suggests we may be looking at a hitherto unknown web of overseas links that marked the beginning of the connected world we know today, centuries before the first farmers reached the central Mediterranean.

Understanding how these groups remained ecologically resilient, while also shaping ecosystems to their needs, may yet prove to have important lessons for humanity’s current and future challenges in a rapidly warming world. As we continue to unravel Malta’s unprecedented hunter-gatherer past, we hope to shed light on this lost ecological knowledge.

The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.