Humanity’s greatest challenge in becoming a multi-planet species may not be building bigger rockets or landing astronauts on Mars. Instead, it could come down to the question: Can humans safely conceive, carry pregnancies, and raise healthy children off Earth?

A new review published in Frontiers in Space Technologies argues that the answer to this question remains unclear. Drawing on decades of research on animal reproduction in space alongside emerging advances in artificial intelligence, biotechnology, synthetic biology, and cybernetic systems, the researchers suggest that future generations born off Earth may require technologies far beyond today’s medical capabilities.

In the most speculative sections of the paper, researchers even envision a scenario in which reproduction itself acts as a tool for helping humans gradually adapt to life in space.

Rather than presenting new experiments, the paper synthesizes existing evidence while outlining possible technological pathways that could someday enable permanent human settlements on the Moon, Mars, or even deeper into the solar system.

The central message is that surviving in space is only the first hurdle. Establishing self-sustaining civilizations will ultimately depend on whether human reproduction can succeed under conditions of microgravity, radiation, isolation, and other environmental stresses that evolution never prepared us to face.

“It is proposed that prenatal and early postnatal developmental stages may constitute critical biological windows for facilitating long-term adaptation to space,” researchers write. “Such interactions could ultimately transform reproduction and early development into active drivers of human evolution, contributing to the emergence of biologically distinct populations progressively adapted to diverse space environments.”

Despite more than six decades of human spaceflight, no human has ever conceived or carried a pregnancy in space. Therefore, science has little direct evidence about what would happen if astronauts attempted to start families off Earth. Nearly everything researchers know comes from studies involving animals ranging from sea urchins and fish to frogs, birds, mice, and rats.

The results are encouraging in some respects but troubling in others.

Several non-mammalian species have successfully reproduced in orbit. Medaka fish, for example, became the first vertebrates to reproduce in space, with fertilization rates comparable to those seen on Earth. Yet, even when reproduction occurs successfully, researchers have documented developmental abnormalities in some species, suggesting that space environments can slightly modify embryonic development.

Rodent studies paint an even more complicated picture. Fertilization is not impossible under microgravity, but early embryonic development frequently suffers. Experiments have shown reduced blastocyst formation, slower embryo development, lower live birth rates, and changes in gene expression. Other studies have linked space radiation to DNA damage, genomic instability, and developmental defects affecting the nervous system.

At the same time, some findings show surprising resilience. Mouse embryos cultured aboard the International Space Station have developed into apparently normal blastocysts under certain conditions. In contrast, freeze-dried mouse sperm stored in orbit for months later produced healthy offspring after returning to Earth.

These mixed findings suggest that reproduction may be biologically possible, but far from routine, under space conditions.

In their review, researchers also examined growing evidence that spaceflight affects male and female reproductive health even before conception occurs.

Microgravity and radiation appear capable of disrupting sperm production, reducing testosterone levels, altering ovarian function, impairing egg maturation, and interfering with hormone regulation.

Some studies suggest sperm can still swim under simulated microgravity, but lose their capability to navigate effectively toward an egg. Others report that radiation accelerates the depletion of ovarian follicles and increases DNA damage in reproductive cells.

More concerning is the possibility that some biological changes could be passed to future generations through epigenetic mechanisms. Experiments involving mice have suggested that spaceflight may alter gene regulation in sperm and influence gene expression in offspring, although the long-term significance is still unknown.

For women, pregnancy itself could present an even greater challenge. On Earth, pregnancy requires profound cardiovascular changes that help deliver oxygen and nutrients to a growing fetus. Microgravity, however, causes fluid redistribution, muscle loss, reduced blood volume, bone demineralization, and changes in cardiovascular function that could interfere with placental development and fetal growth. Radiation exposure, oxidative stress, circadian disruption, and limited medical support would only add to those risks.

Researchers argue that simply shielding astronauts from radiation may not be enough. Gravity itself appears to function as a biological signal that influences everything from cell organization to tissue development. That realization carries renewed interest in artificial gravity as a potential solution.

Instead of depending solely on habitats built on the Moon or Mars, future space settlements could include rotating structures that generate centrifugal force to recreate Earth-like gravity.

Such habitats have appeared in science fiction for decades, but researchers suggest they may ultimately become essential for healthy conception, pregnancy, childhood development, and multigenerational life off Earth.

Researchers propose dedicated orbital research platforms where scientists could systematically study reproduction under lunar, Martian, or custom-designed gravity levels before humans attempt permanent settlements.

Artificial intelligence also features prominently in the researchers’ vision of the future. They propose AI-powered “digital twins” capable of integrating biological, physiological, and environmental data to simulate how embryos, pregnancies, and developing children might respond to different gravitational and radiation environments. These computer simulations could help researchers examine scenarios that would be difficult, or ethically impossible, to test directly in humans.

Perhaps the paper’s most futuristic proposal is something the researchers call Synthetic Reproductive Adaptive Enhancement Technology, or SRAET. This speculative concept envisions highly automated reproductive systems combining artificial wombs, advanced reproductive biotechnology, biosensors, AI-assisted monitoring, and predictive developmental modeling into a closed-loop environment capable of supporting conception through birth under carefully controlled conditions.

The framework explores the controversial possibility that future advances in gene editing and synthetic biology could one day help humans adapt biologically to off-world environments.

Researchers emphasize that such ideas are still speculative and acknowledge the enormous ethical, biological, and safety concerns surrounding germline modification, off-target mutations, and multigenerational consequences. Rather than advocating immediate implementation, they present these possibilities as conceptual pathways that justify careful scientific and ethical discussion.

For fans of science fiction, many of these concepts may sound remarkably familiar. Yet, researchers attempt to ground their arguments in existing developmental biology, reproductive medicine, aerospace engineering, and space medicine while clearly distinguishing current evidence from future speculation.

In the end, researchers suggest that the future of human space travel may depend less on propulsion systems than on understanding how life develops under entirely new environmental conditions. If humanity hopes to establish permanent settlements off Earth, science will first need to ensure that future generations are able to begin life safely under alien skies.

“Ultimately, the greatest challenge of human expansion beyond Earth may not be transporting humans into space, but understanding how life itself can develop, adapt, and evolve under space conditions,” researchers write. “In this sense, SRAET would not merely support reproduction beyond Earth; it would represent a developmental biotechnology through which humanity may begin to actively participate in shaping its own evolutionary future.”

Study: Ferraz M, Moeharram L. “Past, present and future of human reproduction and development in space.” Frontiers in Space Technologies. 2026.

Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan.  Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com 

Researchers have demonstrated an unusual new form of 3D printing capable of building entirely new structures directly onto—and even around—existing objects in just seconds. In a series of experiments, the technique printed microscopic fluid channels around embedded glass spheres, fabricated precision gears onto polished steel rods, and even built a miniature lens directly onto the surface of a working LED.

The breakthrough, described in a paper published in Nature Communications, relies on an advanced form of tomographic volumetric additive manufacturing (TVAM) that allows researchers to “overprint” new structures onto components made from a wide range of materials, including metal, glass, and preassembled microfluidic components. Instead of constructing objects layer by layer like conventional 3D printers, the system projects precisely calculated light patterns into a rotating vat of photosensitive resin, causing an entire three-dimensional object to solidify almost simultaneously within seconds.

The advancement could represent a major step toward making volumetric 3D printing practical in real-world manufacturing environments, where new components often must be integrated with parts that already exist.

It additionally highlights the growing sophistication of computational techniques that can accurately model how light behaves as it passes through materials that absorb, scatter, refract, or reflect light.

“Tomographic Volumetric Additive Manufacturing (TVAM) is a light-based 3D printing technique capable of producing centimeter-scale objects within seconds,” researchers write. “This work demonstrates a broad range of overprinting scenarios, where new structures are directly printed onto or around pre-existing components made from different materials.”

Unlike conventional stereolithography or fused-filament printers that gradually build an object from one direction, tomographic volumetric printing projects hundreds of two-dimensional light patterns into a rotating container filled with liquid resin.

As the resin accumulates enough light energy, the desired three-dimensional structure appears almost simultaneously throughout the volume rather than emerging layer by layer. The approach can produce centimeter-scale objects in mere seconds.

However, until now, one of the technology’s greatest challenges has been accurately calculating how light travels through complicated environments.

Existing objects inside the resin can block, scatter, or bend incoming light, degrading print quality. Conventional models often assume these objects are either completely transparent or completely opaque. This is an oversimplification that breaks down in realistic manufacturing scenarios.

To overcome those limitations, the team developed an upgraded computational framework called Dr.TVAM. Built upon physically based ray tracing, the software models how light propagates through materials with different optical properties while simultaneously optimizing the projected light patterns needed to create the desired object.

Because the framework accounts for reflection, refraction, scattering, absorption, and arbitrary container shapes, it can successfully print structures around components that previously would have interfered with the process.

One of the study’s most compelling demonstrations involved manufacturing microfluidic channels directly inside sealed, preassembled square chambers. Microfluidic devices contain microscopic channels that transport tiny volumes of liquids and are widely used in biomedical research, diagnostics, and organ-on-a-chip systems.

Instead of fabricating the channels separately and assembling the device afterward—a process that can introduce contamination or leaks—the researchers successfully printed perfusable channels directly inside an already assembled chamber while accounting for inlet and outlet structures that would otherwise obstruct the light.

They demonstrated straight channels, branching networks, and spiral geometries capable of carrying fluid after fabrication. Supplementary demonstrations showed colored dye successfully flowing through the finished structures.

The researchers then pushed the concept even further by creating what they describe as context-aware printing. In this experiment, they embedded two tiny glass spheres inside a hydrogel-filled chamber, rapidly determined each sphere’s three-dimensional position using two camera images, and generated customized print patterns in less than a minute.

Those optimized projections produced hollow channels connecting each sphere to inlet and outlet ports while simultaneously printing protective cavities around the spheres themselves. The complete workflow—from detecting the embedded objects to generating printing instructions and fabricating the final structure—required less than three minutes.

That ability could eventually enable highly customized biomedical manufacturing, where printers automatically adapt to the precise location of living tissues, organoids, or other biological materials rather than requiring perfect positioning beforehand.

Another experiment highlighted why precisely modeling light matters.

Previous demonstrations of volumetric overprinting treated metal components as though they completely absorbed incoming light. In reality, polished metal reflects and scatters significant amounts of light, creating distortions that reduce print quality.

Researchers tested both assumptions by printing a gear directly onto a polished steel rod. When the software ignored scattered light, the gear’s fine holes became over-polymerized and poorly defined.

After including realistic scattering behavior into the optical model, however, the resulting gear preserved those elaborate features far more accurately, increasing simulated print fidelity substantially. The improvement was confirmed experimentally.

Researchers even went as far as demonstrating that the process could print directly onto an electronic component.

Using an LED-based volumetric printing system, the researchers fabricated both a miniature lens and a small cross-shaped symbol directly onto the surface of a red LED. When illuminated, the printed lens projected the symbol onto a screen, successfully transforming the LED into a tiny optical projector without requiring additional assembly. The experiment showcased how optical elements themselves could potentially be integrated directly onto existing electronic hardware during manufacturing.

Beyond the individual demonstrations, the work additionally underscores an important trend in additive manufacturing: increasingly sophisticated software is becoming just as important as advances in hardware.

Instead of relying on simplified mathematical approximations, the new framework performs physically based optical simulations capable of modeling arbitrary geometries along with material properties.

The software has been released as open source, along with configuration files and experimental data, allowing other researchers to reproduce and expand upon the 3D printing work.

Although the current demonstrations remain laboratory-scale, the possible implications could extend well beyond experimental 3D printing. Biomedical researchers could eventually fabricate sterile microfluidic systems without multi-step assembly. Optical engineers may integrate lenses directly onto light sources. Manufacturers could add custom features to finished components without redesigning entire production processes.

Researchers also note that future improvements could further increase realism through incorporating additional physical effects, including changes in refractive index during polymerization and the diffusion of chemical inhibitors during printing. Those refinements could expand the technology’s accuracy and enable even more complex manufacturing scenarios.

“In summary, Dr.TVAM, our computational framework, has shown to be capable of modeling different optical situations for TVAM,” researchers write. “We believe this significantly expands the application space for TVAM, enabling the creation of complex, functionalized, and multi-component devices from applications in mechanics, optics, or biofabrication.”

Study: Wechsler F, et al. “Overprinting with tomographic volumetric additive manufacturing.” Nature Communications (2026).

Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan.  Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com