“Well, then, we should start by examining fossils from just before and just after each of the extinction events,” I said.
“Precisely,” said Hollus, his eyestalks weaving eagerly.
“Come with me,” I said.
“You have to take the projector with you, if I am to follow,” said Hollus.
I nodded, still getting used to this idea of telepresence, and picked up the small object.
“It will work fine if you place it in a pocket,” he said.
I did so, and then led him down to the paleobiology department’s giant collections room, in the basement of the Curatorial Centre; we didn’t have to go out into any of the public areas of the museum to get there.
The collections room was full of metal cabinets and open shelving holding prepared fossils as well as countless plaster field jackets, some still unopened half a century after they’d been brought to the museum. I started by pulling out a drawer containing skulls of Ordovician jawless fishes. Hollus looked them over, handling them gently. The force fields projected by the holoform unit seemed to define a solidness that precisely matched the alien’s apparent physical form. We bumped into each other a few times as we negotiated our way down the narrow aisles in the collections room, and my hands touched his several times as I passed him fossils. I felt a static tingling whenever his projected form contacted my skin, the only indication that he wasn’t really there.
As he examined the strange, solid skulls, I happened to comment that they looked rather alien. Hollus seemed surprised by the remark. “I” “am” “cur” “i” “ous,” he said, “about” “your” “concepts” “of” “alien” “life.”
“I thought you knew all about that,” I replied, smiling. “Anal probes and so on.”
“We have been watching your TV broadcasts for about a year now. But I suspect you have more interesting material than what I have seen.”
“What have you seen?”
“A show about an academic and his family who are extraterrestrials.”
It took me a moment to recognize it. “Ah,” I said. “That’s 3rd Rock from the Sun. It’s a comedy.”
“That is a matter of opinion,” said Hollus. “I have also seen the program about the two federal agents who hunt aliens.”
“The X-Files,” I said.
He clicked his eyes together in agreement. “I found it frustrating. They kept talking about aliens, but you almost never saw any. More instructive was a graphic-arts production about juvenile humans.”
“I need another clue,” I said.
“One of them is named Cartman,” said Hollus.
I laughed. “South Park. I’m surprised you didn’t pack up and go home after that. But, sure, I can show you some better samples.” I looked around the collections room. Off at the other end, going through our banks of Pliocene microfossils, I could see a grad student. “Abdus!” I called.
The young man looked up, startled. I waved him over.
“Yes, Tom?” he said once he’d reached us, although his eyes were on Hollus, not me.
“Abdus, can you nip out to Blockbuster and get some videos for me?” Grad students were useful for all sorts of things. “Keep the receipt, and Dana will reimburse you.”
The request was strange enough to get Abdus to stop looking at the alien. “Um, sure,” he said. “Sure thing.”
I told him what I wanted, and he scurried off.
Hollus and I continued to look at the Ordovician specimens until noon, then we headed back up to my office. I imagined that intelligence probably required a high metabolism everywhere in the universe. Still, I thought the Forhilnor might be irritated that I had to take a lunch break (and even more irritated that after stopping our work, I ate almost nothing). But he ate when I did—although, of course, he was really dining aboard his mothership, in orbit over Ecuador. It looked strange: his avatar, which apparently duplicated whatever movements his real body was making, went through the motions of transferring food into his eating slit—a horizontal groove in the top of his torso revealed through a gap in the cloth wound around it. But the food itself was invisible, making it look like Hollus was some extraterrestrial Marcel Marceau, miming the process of eating.
I, on the other hand, needed real food. Susan had packed me a can of strawberry-banana Boost and two leftover drumsticks from yesterday’s dinner. I downed the thick beverage and made it halfway through one of the legs. I wished I’d had something different to eat; it felt a little too primal to be using my teeth to tear meat off bones in front of the alien, although, for all I knew, Hollus was stuffing live hamsters into his gullet.
While we ate, Hollus and I watched the videos Abdus had fetched; I’d had the education department deliver a combo VCR-TV unit to my office.
First up was “Arena,” an episode of the original Star Trek series; I immediately froze the image on a picture of Mr. Spock. “See him?” I said. “He’s an alien—a Vulcan.”
“He” “looks” “like” “a” “human” “being,” said Hollus; he could eat and talk at the same time.
“Notice the ears.”
Hollus’s eyestalks stopped weaving in and out. “And that makes him an alien?”
“Well,” I said, “of course it’s a human actor playing the part—a guy named Leonard Nimoy. But, yeah, the ears are supposed to suggest alienness; this show was done on a low budget.” I paused. “Actually, Spock there is only half-Vulcan; the other half is human.”
“How is that possible?”
“His mother was a human; his father was a Vulcan.”
“That does not make sense biologically,” said Hollus. “It would seem more likely that you could crossbreed a strawberry and a human; at least they evolved on the same planet.”
I smiled. “Believe me, I know that. But wait, there’s another alien in this episode.” I fast-forwarded for a time, then hit the play button again.
“That’s a Gorn,” I said, pointing to the tailless green reptile with compound eyes wearing a gold tunic. “He’s the captain of another starship. Pretty neat, huh? I always loved that one—reminded me of a dinosaur.”
“Indeed,” said Hollus. “Which means, again, that it is far too terrestrial in appearance.”
“Well, it’s an actor inside a rubber suit,” I said.
Hollus’s eyes regarded me as if I were again being Master of the Bleeding Obvious.
We watched the Gorn stagger around for a bit, then I ejected the tape and put in “Journey to Babel.” I didn’t fast-forward, though; I just let the teaser unfold. “See them?” I said. “Those are Spock’s parents. Sarek is a full-blooded Vulcan, and Amanda, the woman there, is a full-blooded human.”
“Astonishing,” said Hollus. “And humans believe such cross-breeding is possible?”
I shrugged a little. “Well, it’s science fiction,” I said. “It’s entertainment.” I fast-forwarded to the diplomatic reception. A stocky snout-nosed alien accosted Sarek: “No, you,” he snarled. “How do you vote, Sarek of Vulcan?”
“That’s a Tellarite,” I said. Then, remembering: “His name is Gay.”
“He looks like one of your pigs,” said Hollus. “Yet again, too terrestrial.”
I fast-forwarded some more. “That’s an Andorian,” I said. The screen showed a blue-skinned, white-haired male humanoid, with two thick, segmented antennae emerging from the top of his head.
“What is his name?” asked Hollus.
It was Shras, but for some reason I was embarrassed that I knew that. “I don’t remember,” I said, then I put in another tape: the special-edition version of Star Wars, letterboxed. I fast-forwarded to the cantina sequence. Hollus liked Greedo—Jabba’s insectlike henchman who confronted Han Solo—and he liked Hammerhead and a few of the others, but he still felt that humanity had missed the boat on coming up with realistic portrayals of extraterrestrial life. I certainly didn’t disagree.
“Still,” said Hollus, “your filmmakers did get one thing right.”
 
; “What’s that?” I asked.
“The diplomatic reception; the scene in the bar. All the aliens shown seem to have about the same level of technology.”
I furrowed my brow. “I always thought that was one of the least believable things. I mean, the universe is something like twelve billion years old—”
“Actually, it is 13.93422 billion,” said Hollus, “measured in Earth years, of course.”
“Well, fine. The universe is 13.9 billion years old, and Earth is only 4.5 billion years old. There must be planets much, much older than ours, and much, much younger. I’d expect some intelligent races to be millions if not billions of years more advanced than we are, and some to be at least somewhat more primitive.”
“A race even a few decades less advanced than you are would not have radio or spaceflight and therefore would be undetectable,” said Hollus.
“True. But I’d still expect lots of races to be much more advanced than we are—like, well, like yourself, for instance.”
Hollus’s eyes looked at each other—an expression of surprise? “We Forhilnors are not greatly advanced beyond your race—perhaps a century at most; certainly no more than that. I expect that within a few decades your physicists will make the breakthrough that will allow you to use fusion to economically accelerate ships to within a tiny fraction of the speed of light.”
“Really? Wow. But—but how old is Beta Hydri?” It would be quite a coincidence if it were the same age as Earth’s sun.
“About 2.6 billion Earth years.”
“A little over half as old as Sol.”
“Sol?” said Hollus’s left mouth.
“That’s what we call our sun, when we want to distinguish it from other stars,” I said. “But if Beta Hydri is that young, I’m surprised that you have any vertebrates on your world, let alone any intelligent life.”
Hollus considered this. “When did life first emerge on Earth?”
“We certainly had life by 3.8 billion years ago—there are fossils that old—and it may have been here as far back as four billion years ago.”
The alien sounded incredulous. “And the first animals with spinal columns appeared just half a billion years ago, no? So it took perhaps as much as 3.5 billion years to go from the origin of life to the first vertebrates?” He bobbed his torso. “Life originated on my world when it was 350 million years old, and vertebrates appeared just 1.8 billion years later.”
“I wonder why it took so much longer here?”
“As I told you,” said Hollus, “the development of life on both our worlds was manipulated by God. Perhaps his or her goal was to have multiple sapient lifeforms emerge simultaneously.”
“Ah,” I said dubiously.
“But, even were that not true,” said Hollus, “there is another reason for all space-faring races to be comparably advanced.”
Something was tickling at the back of my mind, something I’d once seen Carl Sagan explain on TV: the Drake equation. It had several terms, including the rate of star formation, the fraction of stars that might have planets, and so on. By multiplying all the terms together, you were supposed to be able to guesstimate the number of intelligent civilizations that might currently exist in the Milky Way. I can’t remember all the terms, but I do remember the final one—because it chilled me when Sagan discussed it.
The final term was the lifetime of a technological civilization: the number of years between the development of radio broadcasting and the extinction of the race. Humans had first started broadcasting in earnest in the 1920s; if the Cold War had turned hot, our tenure as a technological species might have been as little as thirty years.
“You mean the lifetime of a civilization?” I said. “The span before it blows itself up?”
“That is one possibility, I suppose,” said Hollus. “Certainly, my own race had a difficult time learning to use nuclear power wisely.” The alien paused. “I am given to understand that many humans suffer from mental problems.”
I was startled by the apparent change of topic. “Umm, yes. I suppose that’s true.”
“As do many Forhilnors,” said Hollus. “It is another concern: as technology advances, the ability to destroy the entire race becomes more accessible. Eventually, it is in the hands not just of governments but also individuals—some of whom are unbalanced.”
That was a staggering thought. A new term in the Drake equation: f-sub-L, the fraction of members of your race who are loony.
The Hollus simulacrum moved a little closer to me. “But that is not the principal issue. I told you that my race, the Forhilnors, had made contact with one other technological race, the Wreeds, prior to meeting you; we actually first met them about sixty years ago—by going to Delta Pavonis and discovering them.”
I nodded.
“And I told you that my starship, the Merelcas, visited six other star systems, besides the Wreed home one, before arriving here. But what I did not tell you was that each of those six had, at one time, been home to an intelligent race of its own: the star you call Epsilon Indi, the star you call Tau Ceti, the star you call Mu Cassiopeiae A, the star you call Eta Cassiopeiae A, the star you call Sigma Draconis, and the star you call Groombridge 1618 all once had native intelligent life.”
“But they don’t anymore?”
“Correct.”
“What did you find?” I asked. “Bombed-out ruins?” My mind filled with visions of bizarre alien architecture, twisted and melted and charred by nuclear blasts.
“Never.”
“Then what?”
Hollus spread his two arms and bobbed his torso. “Abandoned cities, some immensely old—some so old, they had been deeply buried.”
“Abandoned?” I said. “You mean the inhabitants had gone somewhere else?”
The Forhilnor’s eyes touched in affirmation.
“Where?”
“That question still vexes.”
“Do you know anything else about the other races?”
“A great deal. They left many artifacts and records behind, and in some cases interred or fossilized bodies.”
“And?”
“And, at their ends, all were comparably advanced; none had built machines we could not understand. True, the variety of body plans was fascinating, although they all were—what is that phrase humans use?—‘life as we know it.’ They were all carbon-based DNA lifeforms.”
“Really? Are you and the Wreeds also DNA-based?”
“Yes.”
“Fascinating.”
“Perhaps not,” said Hollus. “We believe that DNA is the only molecule capable of driving life; no other substance has its properties of self-replication, information storage, and compactibility. DNA’s ability to compress into a very small space makes it possible for it to exist in the nucleuses of microscopic cells, even though when stretched out, each DNA molecule is more than a meter long.”
I nodded. “In the evolution course I used to teach, we considered whether anything other than DNA could do the job; we never came up with an alternative that was even remotely suitable. Did all the alien DNA use the same four bases: adenine and thymine, guanine and cytosine?”
“Are those these four?” said Hollus. Suddenly, his holoform projector made four chemical formulas float in the air between us in glowing green:
C5H5N5
C5H6N2O2
C5H5N5O
C4H5N3O
I peered at them; it’d been a while since I’d done any biochemistry. “Umm, yes. Yes, those are they.”
“Then, yes,” said Hollus. “Everywhere we have found DNA, it uses those four bases.”
“But we’ve shown in the lab that other bases could be used; we’ve even made artificial DNA that uses six bases, not four.”
“Doubtless extraordinary intervention was required to accomplish that,” said Hollus.
“I don’t know; I guess.” I thought about everything. “Six other worlds,” I said, trying to picture them in my mind.
Alien planets.
br /> Dead planets.
“Six other worlds,” I said again. “All deserted.”
“Correct.”
I sought the right word. “That’s…frightening.”
Hollus did not dispute this. “In orbit around Sigma Draconis II,” he said, “we found what seemed to be a fleet of starships.”
“Do you suppose invaders had wiped out the indigenous life?”
“No,” said Hollus. “The starships were clearly built by the same race that had constructed the abandoned cities on the planet below.”
“They built starships?”
“Yes.”
“And they all left the planet?”
“Apparently.”
“But without using the starships, which were left behind?”
“Exactly.”
“That’s…mysterious.”
“It certainly is.”
“What about the fossil records on these planets? Do they have mass extinctions that coincide with ours?”
Hollus’s eyestalks moved. “That is difficult to say; if one could easily read fossil records without decades or centuries of searching, I never would have had to reveal myself to you. But as far as we have been able to tell, no, none of the abandoned worlds had mass extinctions at 440, 365, 225, 210, and 65 million years ago.”
“Were any of those civilizations contemporaneous?”
Hollus’s command of English was remarkable, but occasionally it did fail him. “Pardon?”
“Did any of them live at the same time as any of the others?”
“No. The oldest seems to have ended three billion years ago; the most recent, on the third planet of Groombridge 1618, about five thousand years ago. But…”
“Yes?”
“But, as I said, all the races seemed to be comparably advanced. Architectural styles varied widely, of course. But, to give you an example, our engineers dismantled one of the orbiting starships we found at Sigma Draconis II; it used different solutions to several problems from the ones we employ, but it was not fundamentally much better—perhaps a few decades beyond what we had developed. That is the way it was for all the races that had abandoned their worlds: they were all only slightly more advanced than the Wreeds or the Forhilnors—or Homo sapiens, for that matter.”