Prologue

"Today marks a historic turning point in human civilization."

"At 15:46 today, a paleontological fossil excavation team organized by NASA and sent to Mars unearthed a large number of neatly arranged humanlike skeletal fossils in the foundation tunnels of a Mars base."

"To help answer some of our questions, we've invited Professor Huo Gu, who is directing the excavation remotely from the International Space Center."

As soon as the host finished speaking, the screen changed. The host's image shrank to a small window, and an elegant, easygoing man nearing sixty appeared before the public.

"Hello, Professor Huo," the host said.

"Hello, host," Huo Gu replied.

"Professor Huo, could you tell us about the latest findings from your research into the humanlike skeletal fossils excavated on Mars? It's safe to say that everyone with internet access around the world is following this story."

"Certainly."

Huo Gu nodded slightly. "To preserve the integrity of the fossil group while gathering as much information as possible in a short time, we're conducting a targeted excavation of one of the humanlike skeletal fossils."

"Based on this, we can also conclude that humanity is not alone in the universe."

"Because they're Martians?" the host asked.

Huo Gu shook his head.

"No. The owners of these humanlike skeletons weren't native to Mars, either. They came from another planet and belonged to an ecosystem separate from Mars's."

His words stunned everyone. The host's eyes widened noticeably.

The host's breathing and voice grew somewhat hurried. "Then which planet did these humanlike skeletons come from? And what evidence supports this conclusion?"

Huo Gu said, "Life on a planet can take many forms, but if you trace them back to their origins, you'll find that they share a common ancestor in their evolutionary history. Those of us who study 'Martian biology' call the species at the root of this evolutionary tree the 'foundation species.'"

"Um... Could you put that in simpler terms?" The host looked a little embarrassed.

"Take Earth, for example. Its early environment changed into one rich in oxygen. Since then, the dominant life forms in Earth's biosphere have relied on consuming oxygen to sustain their vital functions."

"The same principle applies to Mars. The dominant forms of ancient Martian life had 'exoskeletons,' with bones encasing their organs and supporting their skin and muscle tissue. Under that system, a Martian would weigh 1.5 times as much as an ordinary person of the same size. But these humanlike skeletal fossils don't fit that pattern. Their bone structures are much more similar to those of Earth's life forms."

"I see."

The host nodded in a daze, though it was hard to tell whether he'd understood.

"Then were these creatures intelligent when they were alive?" the host asked.

"I can answer that with certainty: yes," Huo Gu replied.

"Each body was arranged in neat rows, forming a vast, square fossil bed. It's extremely similar to the 'burial grounds' found on Earth."

"From this, we've deduced that they were intelligent—and not unintelligent, either. At the very least, they had reached the Stone Age."

Suddenly, the host's expression grew serious. He pressed one hand against his earpiece and listened intently for a moment before speaking.

"Professor Huo, a question just posted online has surpassed one billion views in an instant, and the number is still rising rapidly. Could we ask you about it?"

"Of course," Huo Gu replied with a smile.

"What do you think about 'time travel'? Is it possible these humanlike skeletons belonged to our human ancestors, who traveled back in time and ended up on Mars?"

Huo Gu shook his head with an amused laugh.

"No, that's impossible. I only said they were similar to Earth life, not identical. The owners of these skeletons and Earth's life forms belonged to different systems."

As he spoke, an image appeared in the lower-right corner of the screen. The skeleton looked remarkably similar to a human one. The most noticeable difference was a hole in its forehead.

"As you can see, there's a hole in the center of the skeleton's forehead. It wasn't caused by damage to the skull. According to our computer analysis comparing the internal cranial structures, this hole is essentially identical in structure to the other two eye sockets. From this, we've concluded that it was an eye socket."

"In other words, the owner of the skeleton was a humanlike creature with three eyes."

"As I mentioned earlier, according to the 'foundation species' theory, no species on Earth has had three eyes from the very beginning of life to the present day."

"In addition, the excavation team on Mars conducted a simple measurement of the fossils' radioactive decay. They are over 200 million years old. At that time, dinosaurs still ruled Earth."

"But the skeleton looks so much like a human's. How do you explain that? Isn't it completely unbelievable?" the host pressed, unwilling to give up.

"There's nothing strange about similar skeletons. A careful comparison makes it easy to spot the differences between the two, apart from the eye socket in the forehead. Humans and chimpanzees also have very similar skeletons. Does that mean humans and chimpanzees look so alike that you can't tell them apart?"

Huo Gu hesitated, then added, "Host, I do have some thoughts of my own about 'time travel.'"

"Please, go ahead."

The host perked up, his eyes shining.

"Before that, let's first assume that 'time travel' is a real possibility."

"We all know the universe is huge—immense. The observable universe alone is currently 93 billion light-years across, and our Milky Way is enormous, too, containing roughly 100 billion stars."

"Then there's our Solar System. If we take Neptune as the boundary, its average radius is over 30 astronomical units. In other words, if I were the unit of measurement, you could fit roughly 450.4 billion of me across it."

"On top of that, celestial bodies are constantly changing position. Our home planet orbits the Sun at a speed of 29.783 kilometers per second."

"It's hard to imagine that something like time travel could happen so coincidentally on Earth—and even more coincidentally, that among all Earth's life forms, humans would be chosen to travel through time, and then survive with their most basic life functions intact. It's simply too coincidental to believe."

"Professor Huo, you don't think 'time travel' is actually possible, do you?" the host asked.

Huo Gu smiled without committing himself.

"Why would you say that?"

"In probability theory, the probability of something that hasn't happened is never zero. Who knows? Maybe someday, someone really will travel through time, just like in a novel."

"What I mean is, if time travel really does happen someday, I'm more inclined to believe it would be a deliberate event, caused by the intentional actions of some unknown civilization in the universe, rather than an accident..."

"Professor Huo?"

The sudden turn of events caught the host completely off guard. It took him a while to react before he turned his head and shouted, abandoning all concern for appearances.

"Call 120!"