“Yes,” said Ponter. “When an iron-nickel meteor slams into the Earth, the impact aligns the meteor’s magnetic field.”
Arnold frowned. “I suppose it would, at that. Just like hitting an iron bar with a hammer and turning it into a magnet.”
“Exactly,” said Ponter. “But if you did not learn of this from meteorites, how did your people come to know that Earth’s magnetic field periodically reverses?”
“Sea-floor spreading,” replied Arnold.
“What?” said Ponter
“Do you know about plate tectonics?” asked Arnold. “You know, continental drift?”
“The continents drift?” said Ponter, making his face agog. But then he held up a hand. “No, that time I was making a joke. Yes, my people know this. After all, the coastlines of Ranilass and Podlar clearly once were attached to each other.”
“You must mean South America and Africa,” said Arnold, nodding. He smiled ruefully. “Yes, you’d think it would be blindingly obvious to everyone, but it took decades for our people to accept the notion.”
“Why?”
Arnold spread his arms. “You’re a scientist; surely you understand. The old guard thought they knew how the world worked, and they weren’t about to give up their theories. As with so many paradigm shifts, it wasn’t really a case of convincing anyone to change their minds. Rather, it was waiting for the previous generation to pass on.”
Ponter tried to conceal his astonishment. What an extraordinary approach to science these Gliksins had!
“In any event,” continued Arnold, “we ultimately found proof for continental drift. At the middle of the oceans there are places where magma wells up from the mantle, forming new rock.”
“We surmised such things must exist,” said Ponter. “After all, since there are places where old rock is pushed down—”
“Subduction zones,” supplied Arnold.
“As you say,” said Ponter. “If there are places where old rocks go down, we knew there must be places where new rock comes up, although, of course, we have never seen them.”
“We’ve taken core samples from them,” said Arnold.
Ponter’s face went honestly agog this time. “In the middle of the oceans?”
“Yes, indeed,” said Arnold, clearly glad for once that his side was coming out ahead. “And if you look at rocks on both sides of the rifts from which magma is welling up, you see symmetrical patterns of magnetism—normal on either side of the rift, reversed equal distances to the left and right of the rift, normal again on either side but farther out, and so on.”
“Impressive,” said Ponter.
“We have our moments,” said Arnold. He grinned, and was clearly inviting Ponter to do the same.
“Sorry?” said Ponter.
“It’s a pun; a play on words. You know: ‘magnetic moment’—the product of the distance between a magnet’s poles and the strength of either pole.”
“Ah,” said Ponter. This Gliksin obsession with word play…he would never understand it.
Arnold looked disappointed. “Anyway,” he said, “I’m surprised that your magnetic field collapsed before ours did. I mean, I understand the Benoît model: that this universe split from your universe forty thousand years ago, at the dawn of consciousness. Fine. But I can’t see how anything your people or mine might have done in the last four hundred centuries could have possibly affected the geodynamo.”
“It is puzzling,” agreed Ponter.
Arnold clambered off his chair and rose to his feet. “Still, because of it, you’ve been able to satisfy my particular concern better than I would have thought possible.”
Ponter nodded. “I am glad. You should indeed—how would you phrase it?—you should sail effortlessly through the period of magnetic-field collapse.” He blinked. “After all, we certainly did.”
Chapter Twelve
Mary tried to concentrate on her work, but her thoughts kept turning to Ponter—not surprisingly, she supposed, since Ponter’s DNA was precisely what she was working on.
Mary cringed every time she read a popular article that tried to explain why mitochondrial DNA is only inherited from the maternal line. The explanation usually given was that only the heads of sperm penetrate eggs, and only the midsections and tails of sperm contain mitochondria. But although it was true that mitochondria were indeed deployed that way in sperm, it wasn’t true that only the head made it into the ovum. Microscopy and DNA analyses both proved that mtDNA from the sperm’s midsection does end up in fertilized mammalian eggs. The truth was no one knew why the paternal mitochondrial DNA isn’t incorporated into the zygote the way maternal mitochondrial DNA is; for some reason it just disappears, and the explanation that it had never gotten in there in the first place was nice and pat, but absolutely not true.
Still, since there were thousands of mitochondria in each cell, and only one nucleus, it was much easier to recover mitochondrial rather than nuclear DNA from ancient specimens. No nuclear DNA had ever been extracted from any of the Neanderthal fossils known from Mary’s Earth, and so Mary had been concentrating on studying Ponter’s mitochondrial DNA, comparing and contrasting it with Gliksin mtDNA. But there didn’t seem to be any one sequence she could point to that was present in Ponter and the known fossil Neanderthal mitochondrial DNA, but in none of the Gliksins, or vice versa.
And so Mary at last turned her attention to Ponter’s nuclear DNA. She’d thought it would be even more difficult to find a difference there, and indeed, despite much searching, she hadn’t found any sequence of nucleotides that was reliably different between Neanderthals and Homo sapiens sapiens; all her primers matched strings on DNA from both kinds of humans.
Bored and frustrated, waiting for Ponter to be released from quarantine, waiting to renew their friendship, Mary decided to make a karyotype of Neanderthal DNA. That meant culturing some of Ponter’s cells to the point where they were about to divide (since that’s the only time that chromosomes become visible), then exposing them to colchicine to immobilize the chromosomes at that stage. Once that was done, Mary stained the cells—the word “chromosomes,” after all, meant “colored bodies,” referring to their tendency to easily pick up dye. She then sorted the chromosomes in descending order of size, which was the usual sequence for numbering them. Ponter was male, and so had both an X and a Y chromosome, and, just as in a male of Mary’s kind, the Y was only about one-third the size of the X.
Mary arrayed all the pairs, photographed them, and printed out the photo on an Epson inkjet printer. She then started labeling the pairs, beginning with the longest, and working her way to the shortest: 1, 2, 3…
It was straightforward work, the kind of exercise she’d put her cytogenetics students through each year. Her mind wandered a bit while she was doing it: she found herself thinking about Ponter and Adikor and mammoths and a world without agriculture and…
Damn!
She’d obviously screwed up somehow, since Ponter’s X and Y chromosomes were the twenty-fourth pair, not the twenty-third.
Unless…
My God, unless he actually had three chromosome 21s—in which case he, and presumably all his people, had what in her kind produced Down’s syndrome. That made some sense; those with Down’s had an array of facial morphologies that differed from other humans, and—
Good grief, thought Mary, could it be so simple? Down’s sufferers did have an increased incidence of leukemia…and wasn’t that what Ponter said had killed his wife? Also, Down’s syndrome was associated with abnormal levels of thyroid hormones, and those were well-known to affect morphology—especially facial morphology. Could it be that Ponter’s people all had trisomy 21—one small change, manifesting itself slightly differently in them than it did in Homo sapiens sapiens, accounting for all the differences between the two kinds of humans?
But no. No, that didn’t make sense. Principal among Down’s effects, at least in Homo sapiens sapiens, was an under development of muscle tone; Ponter’s people had exa
ctly the opposite condition.
And, besides, Mary had spread out an even number of chromosomes in front of her; Down’s syndrome resulted from an odd number. Unless she’d accidentally brought some chromosomes in from another cell, it appeared that Ponter did indeed have twenty-four pairs, and…
Oh, my God, thought Mary. Oh, my God.
It was even more simple than she’d thought.
Yes, yes, yes!
She had it!
She had the answer.
Homo sapiens sapiens had twenty-three pairs of chromosomes. But their nearest relatives, at least on this Earth, were the two species of chimpanzees, and—
And both species of chimps had twenty-four pairs of chromosomes.
Genus Pan (the chimps) and Genus Homo (humans of all types, past and present) shared a common ancestor. Despite the popular fallacy that humans had evolved from apes, in fact, apes and humans were cousins. The common ancestor—the elusive missing link, not yet conclusively identified in the fossil record—had existed, according to studies of the genetic divergence between humans and apes, something like five million years ago in Africa.
Since chimps had twenty-four pairs of chromosomes and humans had twenty-three, it was anyone’s guess as to what number the common ancestor had possessed. If it had had twenty-three, well, then, sometime after the ape-human split, one chromosome must have become two in the chimp line. If, on the other hand, it had had twenty-four, then two chromosomes must have fused together somewhere along the Homo line.
Until today—until right now, until this very second—no one on Mary’s Earth had known for sure which scenario was correct. But now it was crystal clear: common chimps had twenty-four pairs of chromosomes; bonobos—the other kind of chimp—had twenty-four as well. And now Mary knew that Neanderthals also had an even two dozen. The consolidation of two chromosomes into one had happened long after the ape-human split; indeed, it had happened sometime after the Homo branch had bifurcated into the two lines she was now studying, only a couple of hundred thousand years ago.
That was why Ponter’s people still had the huge strength of apes, rather than the puniness of humans. That was why they had ape physiognomy, with browridges and no chins. Genetically, they were apelike, at least in chromosome count. And something about the fusing of two chromosomes—it was numbers two and three, Mary knew, from studies of primate genetics she’d read years before—had caused the morphological differences that gave rise to the adult human form.
Indeed, the particular cause of the differences was easy enough to identify: it was neoteny, the retention into adulthood of childhood characteristics. Baby apes, baby Neanderthals, and baby Gliksins all had similar skulls, with vertical, ridgeless foreheads, and no particular protrusion of the lower face. As the other kinds grew, their skull shapes changed. But Mary’s kind alone retained their childlike crania into adulthood.
But Ponter’s people did mature cranially. And the differing chromosome count might be the cause.
Mary pressed her two hands together in front of her face. She had done it! She had found what Jock Krieger wanted, and—
And… my God.
If the chromosome counts differed, then Neanderthals and her flavor of Homo sapiens weren’t just different races, or even just subspecies of the same species. They were fully separate species. No need to double up the “wisdom” part in Homo sapiens sapiens to distinguish Mary’s kind from Ponter’s, for Ponter’s people couldn’t possibly be Homo sapiens neanderthalensis. Rather, they were clearly their own specific tax on, Homo neanderthalensis. Mary could think of some paleoanthropologists who would be thrilled by this news—and others who would be extremely pissed off.
But…
But…
But Ponter belonged to another species! Mary had seen Showboat when it was on stage in Toronto; Cloris Leachman had played Parthy. She knew that miscegenation was once a big issue, but…
But miscegenation wasn’t the appropriate term for a human mating with something from outside her own species—not that Ponter and Mary had done that, of course.
No, the appropriate term was…
My God, thought Mary.
Was bestiality.
But…
No, no.
Ponter wasn’t a beast. The man who had raped her—Mary’s conspecific, a member of Homo sapiens —had been a beast. But Ponter was no animal.
He was a gentleman.
A gentle man.
And, regardless of chromosome count, he was a human being—a human being she was very much looking forward to seeing again.
Chapter Thirteen
Finally, after three days, the specialists from the Laboratory Centre for Disease Control and the Centers for Disease Control and Prevention—the comparable U.S. agency—agreed that Ambassador Tukana Prat and Envoy Ponter Boddit were free of infection and could leave quarantine.
Ponter and Tukana, accompanied by five soldiers and Dr. Montego, trudged down the mining tunnel to the metal-cage elevator, and made the long ride to the surface. Apparently, word had preceded them that they were on the way up; a large number of miners and other Inco workers had assembled in the huge room up top that contained the elevator station.
“There is a crowd of reporters waiting in the parking lot,” said Hélène Gagné. “Ambassador Prat, you’ll need to make a brief statement, of course.”
Tukana lifted her eyebrow. “What sort of statement?”
“A greeting. You know, the usual diplomatic thing.”
Ponter had no idea what that meant, but, then again, it wasn’t his job. Hélène led Tukana and him out of the large room and through the doors into the Sudbury autumn. It was at least two degrees hotter than the world Ponter had left behind, maybe more, but, of course, three days had passed while they were underground; the difference in temperature didn’t necessarily mean anything.
Still, Ponter shook his head in amazement. He’d never exited this place while conscious before; the only previous time he’d come up from the mine, he’d been knocked out with a head wound. But now he had a chance to really see the giant mining site, the great tear in the ground these humans had made; the huge stretches of land from which all trees had been cleared; the vast—“parking lot,” they called it, covered with hundreds of personal vehicles.
And the smell! He reeled at the overpowering stench of this world, the nauseating reek. Adikor’s woman, Lurt, had explained the likely sources of the odors, based on Ponter’s descriptions of them: nitrogen dioxide, sulfur dioxide, and other poisons given off by the burning of petrochemicals.
Ponter had warned Tukana about what to expect, and she was discreetly trying to cover her nose with her hand. Still, as much as he fondly remembered the people here, Ponter had forgotten—or suppressed—his memories of what a truly awful job they had done of looking after their version of the planet.
Jock Krieger sat at his desk, surfing the two Webs—the public one, and the vast array of classified government sites, available over dedicated fiber-optic lines, that only those with appropriate security clearance could access.
Jock had never liked it when something came up that he didn’t understand; the only thing that made him feel a lack of control was ignorance. And so he was trying to rectify that by searching for information about geomagnetic collapses, especially with the word from Sudbury that apparently such things happened very quickly.
Jock had expected there to be thousands of Web pages devoted to this topic, and although all the news sites had cobbled together something in the last week, mostly regurgitating the same three or four “expert” opinions, there were really very few concrete studies of this phenomenon. Indeed, about half the hits he found on the World Wide Web were so-called creation scientists trying to explain away the evidence for prehistoric geomagnetic reversals, apparently because the sheer number of them would have taken up too much time if the Earth was only a few thousand years old.
But a citation for one real paper caught Jock’s eye, a 1989 piece from E
arth and Planetary Science Letters called “Evidence Suggesting Extremely Rapid Field Variation During a Geomagnetic Reversal.” The authors were listed as Robert S. Coe and Michel Prévot, the former from the University of California at Santa Cruz, and the latter from the Université des Sciences et Techniques at Montpelier—the one in France, Jock presumed, rather than the one in Vermont. UCSC was definitely a legit institution, and the other one—a few clicks of the mouse—yes, it was on the up-and-up, too. But the damn article wasn’t online; like so much of the world’s wisdom pre-1990, apparently no one had bothered to computerize it. Jock sighed. He’d have to go to an actual library to get a copy.
Mary went down the corridor, then down the staircase, to Jock Krieger’s office on the first floor. She knocked, waited for him to call out “Come in,” and then did just as he had said.
“I’ve got it,” said Mary.
“Well, then, keep your distance,” said Jock, closing his Web browser window.
Mary was too excited even to get the joke then, although it came to her later that day. “I’ve figured out how to distinguish Gliksins from Neanderthals.”
Jock rose from his Aeron chair. “Are you sure?”
“Yes,” said Mary. “It’s a piece of cake. Neanderthals have twenty-four pairs of chromosomes, whereas we have only twenty-three. It’s a glaring difference, as big on the genetic level as the difference between male and female.”
Jock’s gray eyebrows arched up toward his pompadour. “If it was that obvious, what took so long?”
Mary explained her misguided preoccupation with mitochondrial DNA.
“Ah,” said Jock, nodding. “Good work. Very good work.”
Mary smiled, but her smile soon faded. “The Paleoanthropology Society is having its annual meeting in a couple of weeks,” she said. “I’d like to present my Neanderthal karyotype there. Someone else is bound to make one sooner or later, but I’d like to get priority.”
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