'Certainly was a break from the norm.'
You're the master of understatement, Nigel. That wasn't a break from the norm; that was some fucked-up shit.'
'I suppose it was,' he said, inwardly rather pleased that his work and the publicity had been noticed. 'Listen, I was wondering: can you help me catch another killer?'
Westerberg's eyes widened. 'Jaysus, what now? You turned into Travis Bickle, cleaning the scum off the streets?'
'The police have asked for my help once more,' he explained, trying to remain modest.
'Who's been killed?' Westerbeg asked.
'That has to remain confidential, I'm afraid,' Nigel said.
'Part of the deal in the police allowing me to come here and explore this with you.'
'I suppose that makes sense. What's the deal?'
'Bear with me on this,' Nigel said. 'I'm a layman, after all. The police have a mtDNA sample that was found at the scene of a murder -- from a strand of hair, I believe. It turns out that it's the same type as the victim, except it came from a male while the victim was female. According to the police's forensic people, the victim and whoever left this hair -- who may or may not be the killer -- shared a common maternal ancestor.'
'Well, we could verify that for you,' Westerberg said.
'Thanks. But that's not why I'm here. The police are, in the original sense of the word, clueless. All they have at the moment is this hair and the mtDNA sample and the fact of the shared maternal ancestry. They've asked me to research the victim's family tree and find out all the people extant who share this mtDNA.'
Westerberg's face clouded over. He leaned forward across the desk. 'Nigel, you do realize that the maternal ancestor you speak of could have lived thousands of years ago? It may not be confined to five or six branches of the family. It may be confined to five or six per cent of the population.'
Nigel nodded. 'That's where you come in. Is it possible from the test you've devised to discover when this ancestor was shared?'
Westerberg shook his head. 'No.'
Damn, Nigel thought. I've wasted my time.
'Unless.'
'Unless what?'
Westerberg sat back. 'Do you have any details about the type extracted from the strand of hair?'
Nigel had. After employing all his powers of persuasion, Heather had agreed to ask Foster whether Nigel could have details of the type of mtDNA extracted from the hair strand. The DCI had agreed, somewhat reluctantly, and an hour later an e-mail containing an impenetrable sequence of numbers had arrived in Nigel's in-box:
16111 16290 16319 16362
Second hypervariable segment 64 146 153
He produced the printout from his jacket pocket and handed it to Westerberg. The scientist stared at it for several seconds. Put it down and stroked his beard.
'You might be in luck,' he said.
'Might I?'
'The group this sample belongs to is a relatively rare one. Which means you won't have vast amounts of people sharing it.'
'How many?'
'I can't answer that. But that's not the only reason you're lucky. Let me check something out.' He tilted the screen of his computer to face him and tapped in a few details.
Studied the screen carefully and then punched in some more data. He started to nod. 'The person to whom this belonged had a maternal ancestor that was Native American.'
'You
can tell that from the piece of paper?'
'It gives the mtDNA haplotype, which means I can assign it to a haplogroup, which means I can work out its biogeographic ancestry.' Westerberg paused, taking a slurp of lukewarm coffee. Nigel noticed the mug. It had a crude drawing of a banana. Written inside were the words 'I share half my DNA with a banana'. He wondered if it was true, making a mental note to check it on the Internet when he got home. 'By examining a person's mtDNA and the mutations it carries, we can follow their ancestor's footprint and their lineage. The ancestor of whoever owned this DNA left a print in North America and it's one we know is shared by other people with Native American ancestry. Give me a day or two to check a few databases and I might even be able to tell you the tribe to which the maternal ancestor may have belonged.'
Nigel was amazed. 'You can tell me whether the victim's ancestor was a Cherokee or a Sioux or an Apache?'
Westerberg smiled. 'Not that specific. Most haplotypes are shared across tribes or are maybe restricted to a related group of tribes, but we could certainly narrow it down.'
He could see Nigel was still impressed. 'I told you genetic genealogy was the future.'
While he found this revelation thrilling, Nigel knew the Native American population was not renowned for keeping records. There was no way he could use this information. Unless . . .
There was little evidence of any Native American blood in Katie Drake's features. The most obvious explanation was that this mysterious woman entered the Drake lineage hundreds of years ago on some great migratory route.
However, another explanation occurred to him.
'Is there any chance of discovering a date or an approximate time when a Native American woman entered the bloodline?'
Westerberg ran his hand through his hair so that it stuck up as if caught by static. 'How would that help?' the Irishman asked, furrowing his brow.
'I'm not sure it would. The fact is, I've been trying to trace the maternal line of the victim as part of the investigation and the paper trail appears to end '
'I knew it!' Westerberg slapped his hand down hard on the desk. 'I knew it! You need me. You've hit a wall and you need a hand to get over it. Hang on, what was it you said in the bar at that ball-aching convention?' He put his hand to his forehead. 'Hang on, I got it, it's coming. "The problem with genetic genealogy, old chap, is that it's a gimmick. A bloody lucrative one, but still a gimmick.'"
Nigel winced as Westerberg, eyes sparkling with delight, slapped the desk a second time to underline his glee.
'So let me get this straight, Nigel. You want me to see if I can find out when the Native American mtDNA entered the bloodline so you can go back to the records and see if you can pick up the trail again?'
'In a nutshell, yes, that'd be very useful'
'You can't do it.'
'Really?'
'Rather, you couldn't do it.'
'Your employment of the past tense seems to imply you now can.'
'Perhaps. I've developed a test, one that isn't even available to customers yet, which hopes to tell you that sort of information. It's simple maths. Testing how far back in the family tree the Native American ancestor came in translates genetically to what proportion of the person's ancestry and therefore genes are Native American. You would expect roughly one-eighth of the genes to be Native American with a great-grandparent, and one-sixteenth if it were a great-great-grandparent.'
'How do you know how much of a person's genes are Native American?'
'The test examines DNA changes which are more common in one continental group of people than another, for instance Africans, East Asians, Europeans or Native Americans. There are hundreds of these DNA changes that can be specific to a continent, but are more often found at a high frequency in one place, for example Native Americans, but at a much lower frequency in another place -- they are markers of ancestry. Forensic identification normally uses about a hundred markers to compile a profile.
Our test uses hundreds of markers across many genes, thus giving people an idea of their overall ancestry. We use a computer program which takes into account the number of each type of change you have and where these are found and how common they are, and calculates this as a percentage of the make-up of your ancestry -- whether it's European, African or Native American. So by pinpointing the amount of Native American DNA in the sample we could work out when those genes entered the family tree.'