A Discovery of Witches - Deborah Harkness [88]
“The world was a different place when there were as many creatures as humans.” Miriam sounded regretful that the genetic deck was no longer stacked in our favor. “But their sensitive immune systems are going to get humans in the end.”
“How different are we—the creatures—from humans?”
“Considerably, at least on the genetic level. We appear similar, but under the surface our chromosomal makeup is distinctive.” Matthew sketched a diagram on the outside of Beatrice Good’s folder. “Humans have twenty-three chromosomal pairs in every cell nucleus, each arranged in long code sequences. Vampires and witches have twenty-four chromosome pairs.”
“More than humans, pinot noir grapes, or pigs.” Marcus winked.
“What about daemons?”
“They have the same number of chromosome pairs as humans—but they also have a single extra chromosome. As far as we can tell, it’s their extra chromosome that makes them daemonic,” Matthew replied, “and prone to instability.”
While I was studying his pencil sketch, a piece of hair fell into my eyes. I pushed at it impatiently. “What’s in the extra chromosomes?” It was as hard for me to keep up with Matthew now as it had been managing to pass college biology.
“Genetic material that distinguishes us from humans,” Matthew said, “as well as material that regulates cell function or is what scientists call ‘junk DNA.’”
“It’s not junk, though,” Marcus said. “All that genetic material has to be left over from previous selection, or it’s waiting to be used in the next evolutionary change. We just don’t know what its purpose is—yet.”
“Wait a minute,” I interjected. “Witches and daemons are born. I was born with an extra pair of chromosomes, and your friend Hamish was born with a single extra chromosome. But vampires aren’t born—you’re made, from human DNA. Where do you acquire an extra chromosome pair?”
“When a human is reborn a vampire, the maker first removes all the human’s blood, which causes organ failure. Before death can occur, the maker gives his or her blood to the one being reborn,” replied Matthew. “As far as we can tell, the influx of a vampire’s blood forces spontaneous genetic mutations in every cell of the body.”
Matthew had used the term “reborn” last night, but I’d never heard the word “maker” in connection with vampires before.
“The maker’s blood floods the reborn’s system, carrying new genetic information with it,” Miriam said. “Something similar happens with human blood transfusions. But a vampire’s blood causes hundreds of modifications in the DNA.”
“We started looking in the genome for evidence of such explosive change,” Matthew explained. “We found it—mutations proving that all new vampires went through a spontaneous adaptation to survive when they absorbed their makers’ blood. That’s what prompts the development of an extra chromosome pair.”
“A genetic big bang. You’re like a galaxy born from a dying star. In a few moments, your genes transform you into something else—something inhuman.” I looked at Matthew in wonder.
“Are you all right?” he asked. “We can take a break.”
“Could I have some water?”
“I’ll get it.” Marcus hopped up from his stool. “There’s some in the specimen fridge.”
“Humans provided the first clue that acute cellular stress from bacteria and other forms of genetic bombardment could trigger quick mutations, rather than the slower changes of natural selection.” Miriam pulled a folder out of a file drawer. Opening it, she pointed to a section of a black-and-white graph. “This man died in 1375. He survived smallpox, but the disease forced a mutation on the third chromosome as his body quickly coped with the influx of bacteria.”
Marcus returned with my water. I took the cap off and drank thirstily.
“Vampire DNA is full of similar mutations resulting from disease resistance. Those changes