Are the Aliens Us? The Time-Traveler Theory of UFOs, Tested

Picture the classic abduction report. A small, hairless figure. A big head. Huge eyes, a tiny nose and mouth. It speaks the witness's language and handles technology that looks advanced, but not unrecognizable.

Most people hear that and think: alien.

Michael P. Masters, a professor of biological anthropology at Montana Technological University in Butte, hears it and thinks: hominin. Specifically, us, a very long way down the road.

In his 2019 book Identified Flying Objects, Masters argues the beings in UFO encounters may be our distant descendants, traveling back in time to study their own evolutionary past.

The anthropologist's argument

The book's full title is Identified Flying Objects: A Multidisciplinary Scientific Approach to the UFO Phenomenon (Masters Creative LLC, 2019). Masters followed it in 2022 with The Extratempestrial Model.

His core reasoning, as reported by Space.com's Leonard David in 2020, goes like this. Science, technology and engineering are changing at an accelerating pace. So it's plausible that humans of the distant future will have the knowledge and machinery to return to the past.

Masters calls those visitors "extratempestrials," beings from outside our time rather than outside our world.

He then points to how close-encounter accounts typically describe the occupants: bipedal, hairless, human-like, with large brains, large eyes, small noses and small mouths. They're often said to communicate in our languages and to use technology advanced beyond ours, but clearly built on it.

To an anthropologist, Masters says, those features look like a continuation of long-term trends in human evolution.

"It is us"

The obvious objection is that aliens from another planet are a simpler answer. Masters flips that.

"I think the simplest explanation, innately, is that it is us. I'm just trying to offer what is likely the most parsimonious explanation."

His reasoning: we know humans exist, we know our evolutionary history is long, and we know our technology will keep advancing. An unknown species from an unknown planet adds more assumptions, not fewer.

He also has a theory of motive. "The alleged abduction accounts are mostly scientific in nature," he told Space.com. "It's probably future anthropologists, historians, linguists that are coming back to get information in a way that we currently can't without access to that technology."

And some of it, he added, may be tourism, with future travelers paying to see their favorite periods of history.

Why the idea has pull

Give it its due. The time-traveler hypothesis tackles real puzzles in a way the standard alien story struggles with.

The bodies. If you were designing an alien from scratch, there's no strong reason it would have two arms, two legs and a face arranged like ours. Jacques Vallée made a similar point in his 1990 critique of the extraterrestrial hypothesis. A future human solves that instantly.

The language. Visitors who speak English to an American farmer are odd if they evolved light-years away. They're less odd if they're descended from people who spoke it.

The interest in us. Abduction narratives are full of examination and sampling. Masters reads that as fieldwork, the same kind of work he has done directing archaeological digs, by researchers with far better tools.

It fits a bigger family of ideas. In 2024, Masters co-wrote a paper in Philosophy and Cosmology with Harvard researchers Tim Lomas and Brendan Case that lists "extratempestrial" visitors as one possible explanation for UFOs, alongside hidden Earth-based civilizations.

Masters is also candid about the limits. He calls the book a tie between known evolutionary history and "what is still an unproven, unverified aspect of UFOs and aliens." And he admits "there are aspects of time that we don't yet understand."

The physics problem

Here's the wall. Traveling into the future is ordinary physics; it's what happens, a tiny bit, to every astronaut moving fast. Traveling into the past is a different story.

Einstein's general relativity permits some exotic solutions with "closed timelike curves," paths through spacetime that loop back on themselves. Whether nature ever allows them is another question.

In 1992, Stephen Hawking published "Chronology protection conjecture" in Physical Review D. He argued that quantum effects would build up and stop such time loops from forming. In his view, the laws of physics do not allow them to appear, a principle that would, as he famously put it, keep the universe safe for historians.

A 1993 analysis by physicist Matt Visser in the same journal looked at the mechanisms that might do the blocking and found that gravitational back-reaction becomes large before the quantum-gravity scale, which supported Hawking's conjecture.

It's called a conjecture for a reason. It hasn't been proven, and physicists still debate it; a 2026 preprint even proposes an optical experiment to test it. But it means the core requirement of the time-traveler hypothesis isn't just unbuilt technology. It may be forbidden.

Hawking also ran a famous informal test. On June 28, 2009, he hosted a party for time travelers at the University of Cambridge and sent the invitations only afterward. Nobody came. He called it "experimental evidence that time travel is not possible," NPR reported. It was a joke, but it makes a serious point: if the past is a tourist destination, where are the tourists?

The paradox problem

Even if past travel is possible, it raises the classic headache. A traveler who changes the past could, in principle, prevent their own existence.

Defenders of time-travel ideas have answers. Some invoke a many-worlds view, where changing the past branches off a new timeline. Others argue for a "block time" picture where the past is fixed and the traveler was always part of it. Both are speculative, and neither is something we can test.

Notice the cost, too. If abductions are field research, the researchers are interfering with their own history on a large scale. That's exactly what a careful time traveler would avoid.

The evolution problem

Masters' strongest card is anthropology. It's also where critics push back.

Human evolution isn't a straight line toward bigger brains and bigger eyes. In 2021, a team led by Jeremy DeSilva argued in Frontiers in Ecology and Evolution that human brain size actually declined about 3,000 years ago. Other researchers disputed that analysis in 2022, and the debate is unsettled. But it shows how hard it is to project our anatomy forward with confidence.

And the "gray alien" face may say more about our culture than our future. UFO researcher Martin Kottmeyer argued in 1990 that Barney Hill's famous hypnotic description of wraparound eyes came 12 days after a The Outer Limits episode, "The Bellero Shield," aired with a similar-looking alien. Others have contested that link. But if the archetype is partly a media product, it's shaky ground for an evolutionary forecast.

What would prove or disprove it

To its credit, the time-traveler hypothesis makes a few claims that could, in principle, be checked.

A biological sample from an encounter that proved to be clearly human, but genetically far beyond our population's variation, would be striking. So would any physical demonstration that closed timelike curves can form.

On the other side, a proof that chronology protection holds, a stronger version of Hawking's conjecture, would make the idea extremely hard to sustain. Until either happens, it stays where Masters himself puts it: a model, not a finding.

What we know, and what we don't

What we know

• Masters published Identified Flying Objects in 2019 and The Extratempestrial Model in 2022, arguing UFO occupants may be future humans.
• Hawking's 1992 chronology protection conjecture argues the laws of physics prevent time loops; it remains unproven.
• Reported entity descriptions often share human-like features, which the hypothesis tries to explain.

What we don't

• Whether travel to the past is physically possible at all.
• How much of the classic "gray" description comes from experience and how much from culture.
• Which way human anatomy will actually evolve over the very long term.

A mirror with a clock in it

The time-traveler theory has an emotional pull that the spaceship story doesn't. It says the strangers aren't strangers. They're family, checking in.

But it trades one giant unknown, interstellar travel, for another that might be worse: a trip physics may never allow. That's not a reason to stop asking. It's a reason to keep the question labeled as a question.

So be honest: if you met one of these visitors, would you rather learn it came from another star, or from your own great-great-great-grandchildren?

Sources

• UFOs May Be Piloted by Time-Traveling Humans, Book Argues — Leonard David, Space.com via Live Science, 2020
• Identified Flying Objects: A Multidisciplinary Scientific Approach to the UFO Phenomenon (repository listing) — Montana Technological University, 2019
• The Extratempestrial Model — Leigh Bureau (Full Circle Press, 2022)
• The cryptoterrestrial hypothesis — Lomas, Case and Masters, Philosophy and Cosmology, 2024
• Chronology protection conjecture — Stephen W. Hawking, Physical Review D, 1992
• From wormhole to time machine: Remarks on Hawking's chronology protection conjecture — Matt Visser, Physical Review D, 1993
• Optical time travel: proposal for testing Hawking's Chronology Protection Conjecture in an optical analogue — arXiv preprint, 2026
• Time travelers invited to Stephen Hawking memorial service — NPR via MPR News, 2018
• When and Why Did Human Brains Decrease in Size? A New Change-Point Analysis and Insights From Brain Evolution in Ants — DeSilva et al., Frontiers in Ecology and Evolution, 2021
• No, the Human Brain Did Not Shrink 3,000 Years Ago — Neuroscience News, 2022
• The Bellero Shield — Wikipedia
• Five Arguments Against the Extraterrestrial Origin of UFOs (text and commentary) — Jacques Vallée, Journal of Scientific Exploration, 1990
• Claim: Time-Travelling Humans are Causing Close Encounter Experiences — Metabunk forum