And now it had happened again, for the second time today. Mary did the three-fingered salute, but after sitting through the interminable wait for the system to reboot, she found that it stubbornly refused to reacquire its network connection.

Mary sighed. It was 7:00P.M. , but she could hardly call it a day; Ponter and Adikor would need her to give them a lift back to Bristol Harbour Village whenever they returned from the hospital.

Of course, there were lots of other computers here in the old mansion that housed the Synergy Group, but, well…

Jock had one of those nifty Aeron chairs Mary had read about in the Sharper Image catalog. It was supposed to be super-comfortable, an ergonomic heaven. Granted, he had probably adjusted all its heights and tilts for his rangy body, but, still, she could get a feel for it if she worked in his office.

Mary got up, and headed down the staircase, which was carpeted in a wine red. Jock’s office door was wide open, and Mary walked in. Jock had a big bay window, looking south over the marina. Mary shivered at the view, despite it still being warm inside.

She walked over to Jock’s super-chair, all black metal and plastic, with a fine-meshed black back that was supposed to allow one’s skin to breathe while seated. Feeling like a mischievous kid, she lowered herself into the chair and leaned back.

My God, she thought. A product for which the hype was actually true! It was wonderfully comfortable. She used her feet to rotate the chair left and right. Mary knew Aerons cost an arm and a leg, but she had to get herself one of these…

After relaxing in the chair for a few more moments, she settled back to work. Jock, who had left this room in a hurry when Lonwis Trob had his heart attack, was still logged onto the network. Mary suspected her own password would work from here, but wasn’t positive, and so she decided to leave well enough alone, and continued working as if she were Jock. She opened up the “Neanderthal genetics” folder on the server, and—

Mary’s eyebrows shot up. She spent most of her time in this folder, but there were two icons displayed that she’d never seen before. She felt nervous: although Mary was pretty good at backing up, she was afraid the crash she’d had upstairs had corrupted the directory tree.

She decided to check by double-clicking on one of the icons she didn’t recognize—it showed a red-and-black double helix. Mary knew most of the genetics apps on the market, and their accompanying document icons, but this one was unfamiliar.

After a moment a window opened. It said “USAMRIID Geneplex—Surfaris” in the title bar, and a screenful of text and formulas appeared below it. USAMRIID was an acronym that appeared often enough in the genetics literature: United States Army Medical Research Institute of Infectious Diseases. And Geneplex was obviously the program’s name. But “Surfaris” didn’t mean a thing to Mary.

Still, she looked at the window’s contents, and was absolutely astonished. Some of her own earlier work here at Synergy had involved trying to use the quorum-counting facility of bacteria to determine an actual tally of how many chromosome pairs were present—twenty-three or twenty-four. But that hadn’t worked. First, the quorum mechanism seemed to lack the ability to distinguish quantities that precisely. And, second, chromosomes only resolved themselves out of the chromatin during mitosis, which, of course, was hardly the usual state of affairs within a cell.

But Jock had apparently had someone else also working on this problem, and that geneticist had come up with a much simpler technique. In a Gliksin, what had been ancestral chromosomes two and three had fused, producing a much longer chromosome. The genes that had been at the end of chromosome two now abutted the genes at the beginning of chromosome three, somewhere in the middle of the new, combined chromosome.

The same genes existed in a Neanderthal, but they did not abut. Rather, the last gene on chromosome two was followed by a telomere—the junk-DNA cap that did nothing but protect the tip of the chromosome, like the little plastic-wrapped bit at the end of a shoelace. Likewise, the first gene in chromosome three was preceded by another telomere, the end cap on the leading edge of that chromosome. So, in a Neanderthal, you’d find these sequences:

Those sequences wouldn’t exist anywhere in Gliksin DNA. Conversely, in Gliksin DNA, millions of base pairs away from any telomere, you’d find this sequence, a combination completely absent from Neanderthal DNA:

A logical extension of Mary’s original work—and a perfect, infallible way of distinguishing between the two kinds of humans, even when a cell wasn’t undergoing mitosis. It was precisely what Jock said he’d wanted: a simple, reliable method to distinguish a Gliksin from a Barast.

Mary was pleased to see that all the tests were invoked. In theory, one could test for only one of the three conditions. Finding either of the first two sequences—either gene ALPHA or gene BETA next to a telomere—clearly denoted Homo neanderthalensis. And finding the third sequence—genes ALPHA and BETA adjacent to each other—denoted Homo sapiens. But things could always go wrong, and so the test to identify a Neanderthal used a little logic tree, explained, presumably for Jock’s benefit, in plain English:

The abort conditions in steps two and three were fail-safes. They occurred if the genes ALPHA and BETA were not side by side (as determined in step one) and neither ALPHA nor BETA were next to a telomere—combinations that should never be found in either kind of hominid DNA.

It was a pig-simple program for a computer to execute, but it was a bit more complex to code into a cascade of biochemical reactions, although apparently that was what Jock’s geneticist had done. Mary had no trouble following the formulas for enzymes produced at each stage of the reaction, and could see that the results would indeed follow the intended logic. At the end of it all, she expected to just see an enzyme or other marker produced whose presence could be easily tested for: an unambiguous flag saying, yup, this is a Neanderthal, or nope, it’s not.