I was right. I remembered to look at Rosie for her reaction. She looked very sad. It seemed we would have to get drunk again.

‘Remember,’ she said, ‘the sample’s not from him; it’s his daughter’s.’

‘I’ve already factored it in.’

‘Naturally. So that’s it.’

‘But we haven’t solved the problem.’ As a scientist I am not accustomed to abandoning difficult problems.

‘We’re not going to,’ said Rosie. ‘We’ve tested everyone I ever heard of.’

‘Difficulties are inevitable,’ I said. ‘Major projects require persistence.’

‘Save it for something that matters to you.’

Why do we focus on certain things at the expense of others? We will risk our lives to save a person from drowning, yet not make a donation that could save dozens of children from starvation. We install solar panels when their impact on CO2 emissions is minimal – and indeed may have a net negative effect if manufacturing and installation are taken into account – rather than contributing to more efficient infrastructure projects.

I consider my own decision-making in these areas to be more rational than that of most people but I also make errors of the same kind. We are genetically programmed to react to stimuli in our immediate vicinity. Responding to complex issues that we cannot perceive directly requires the application of reasoning, which is less powerful than instinct.

This seemed to be the most likely explanation for my continued interest in the Father Project. Rationally, there were more important uses for my research capabilities, but instinctively I was driven to assist Rosie with her more immediate problem. As we drank a glass of Muddy Water Pinot Noir at Jimmy Watson’s before Rosie had to go to work, I tried to persuade her to continue with the project but she argued, rationally enough, that there was now no reason to consider any member of her mother’s graduation class more likely than any other. She guessed that there would be a hundred or more students, and pointed out that thirty years ago, as a result of entrenched gender bias, the majority would be male. The logistics of finding and testing fifty doctors, many of whom would be living in other cities or countries, would be prohibitive. Rosie said she didn’t care that much.

Rosie offered me a lift home, but I decided to stay and drink.

13

Before abandoning the Father Project, I decided to check Rosie’s estimate of the number of father candidates. It occurred to me that some possibilities could be easily eliminated. The medical classes I teach contain numerous foreign students. Given Rosie’s distinctly pale skin, I considered it unlikely that her father was Chinese, Vietnamese, black or Indian.

I began with some basic research – an internet search for information about the medical graduation class, based on the three names I knew.

The results exceeded my expectations, but problem-solving often requires an element of luck. It was no surprise that Rosie’s mother had graduated from my current university. At the time, there were only two medical courses in Melbourne.

I found two relevant photos. One was a formal photo of the entire graduation class, with the names of the one hundred and forty-six students. The other was taken at the graduation party, also with names. There were only one hundred and twenty-four faces, presumably because some students did not attend. Since the gene-shopping had occurred at the party, or after, we would not have to worry about the non-attendees. I verified that the one hundred and twenty-four were a subset of the one hundred and forty-six.

I had expected that my search would produce a list of graduates and probably a photo. An unexpected bonus was a ‘Where are they now?’ discussion board. But the major stroke of luck was the information that a thirtieth anniversary reunion had been scheduled. The date was only three weeks away. We would need to act quickly.

I ate dinner at home and rode to the Marquess of Queensbury. Disaster! Rosie wasn’t working. The barman informed me that Rosie worked only three nights per week, which struck me as insufficient to provide an adequate income. Perhaps she had a day job as well. I knew very little about her, beyond her job, her interest in finding her father and her age, which, based on her mother’s graduation party being thirty years earlier, must be twenty-nine. I had not asked Gene how he had met her. I did not even know her mother’s name to identify her in the photo.

The barman was friendly, so I ordered a beer and some nuts and reviewed the notes I had brought.

There were sixty-three males in the graduation party photo, a margin of only two over the females, insufficient to support Rosie’s claim of discrimination. Some were unambiguously non-Caucasian, though not as many as I expected. It was thirty years ago, and the influx of Chinese students had not yet commenced. There was still a large number of candidates, but the reunion offered an opportunity for batch processing.

I had by now deduced that the Marquess of Queensbury was a gay bar. On the first visit, I had not observed the social interactions, as I was too focused on finding Rosie and initiating the Father Project, but this time I was able to analyse my surroundings in more detail. I was reminded of the chess club to which I belonged when I was at school. People drawn together by a common interest. It was the only club I had ever joined, excluding the University Club, which was more of a dining facility.

I did not have any gay friends, but this was related to my overall small number of friends rather than to any prejudice. Perhaps Rosie was gay? She worked in a gay bar, although the clients were all males. I asked the barman. He laughed.