“Calm down!” Sana ordered. Shawn’s voice had been steadily rising as he spoke. “You and I are having a discussion here, not a debate.”

“Sorry. I’ve been wound up from the moment Rahul placed the codex in my hot little hands.”

“Apology accepted,” Sana said. “Let me ask you another question about Saturninus’s letter. He used the word sealed when referring to Mary’s ossuary. What do you think they meant by ‘sealed’?”

“Offhand, I’d guess wax. Burial practices at that time involved putting a corpse in a cave tomb for a year or so, then collecting the bones and putting them in a limestone box, which they called an ossuary. If the decay wasn’t complete, the box could have stunk to high heaven unless sealed. To do that, they would have had to use something like wax.”

“Saturninus said that Mary’s body was put in a cave in Qumran. How dry is it there?”

“Very.”

“And how dry is it in the necropolis beneath Saint Peter’s?”

“It varies, but there are times when it’s relatively humid. What are you thinking?”

“I’m wondering what kind of condition the bones might be in if the ossuary stayed sealed. If dampness has been excluded, I might be able to harvest a bit of DNA.”

Shawn chuckled with delight. “I’d never even considered that. Getting some DNA could add another dimension to this story. Maybe the Vatican could make some money by creating Bible Land, something akin to Jurassic Park, by bringing back some of the original characters, starting with Mary.”

“I’m being serious,” Sana said, mildly offended, thinking Shawn was making fun of her. “I’m not talking about nuclear DNA, I’m only talking of my area of expertise: mitochondrial DNA.”

Shawn held up his hands, again pretending to surrender. “Now, I know you’ve told me in the past, but I don’t totally remember the difference between the two types of DNA.”

“Nuclear DNA is in the cell’s nucleus, and it contains all the information to make a cell, to allow it to differentiate into, say, a heart cell, and to cause it to function. Every cell has a full complement of nuclear DNA except red blood cells, which have no nucleus. But every cell has only one set. Mitochondria are microscopic energy organelles that in the very distant past when life was just beginning were engulfed by primitive single-cell organisms. Once those single cells had mitochondria, they were able over millions or even billions of years to develop through evolution into multicellular organisms up to and including humans. Since the mitochondria had been freely living organisms, they have their own DNA, which exists in a circular, relatively stable form. And since individual cells have up to a hundred or so mitochondria, the cell has up to a hundred sets of mitochondrial DNA. All that leads to a higher possibility that DNA can be retrievable, even from ancient bones.”

“I’m going to pretend I understood all that. Do you really think you might be able to isolate some of this circular DNA? That would be fascinating.”