My Chanukah present from my husband this year was a test tube, encased in a cardboard box. All I had to do was collect some saliva, and pop it in the post and the website ancestry.com promised the chance to “uncover my ethnic mix, discover distant relatives and find new details about your unique family history.”

The tube sat around in my kitchen for a few weeks, while I dithered about whether I really wanted to do this. My husband (urged by a cousin) had done the same test a few months ago, and received the unsurprising news that his ethnic mix was no mix at all, he was 100 per cent Ashkenazi Jewish. My ethnic origins would surely be the same — although what about my inner suspicions that I was somehow Eastern European? Would I be welcoming distant Ukrainian cousins, descended from some Cossack rapist? And wouldn’t any family history revealed be utterly grim and depressing?

But eventually, curiosity got the better of me. I sent off my spittle and awaited the results. Back they came, no Cossacks to see. One hundred per cent “European Jewish”, with a focus on Western Ukraine, Moldova and Eastern Romania. A very wide focus, geographically, and one that doesn’t fit with known facts (Poland, Eastern Ukraine), but nothing remotely surprising. Not even a hint of Sephardi blood to create some sort of a mix.

On to the site, and the list of new cousins — people whose DNA suggest that they are linked with me through distant great-great ancestors. I couldn’t muster up much interest in these strangers, nice as I am sure they are. In a world so busy that I rarely see my own much-loved first cousins, I’m pretty sure I have no time for extras.

And yet. One completely unknown second cousin had a family tree which gave me the brand new information that our shared great-grandfather Isaac, had died at the age of 91 in 1976. A few clicks on, I was looking at his army recruitment card, from June 1918, when so many young men had died fighting for the United Kingdom that they were calling up 38-year-old Polish tailors of 5’3’’. He wanted to join the Jewish Brigade, but he ended up in a Labour Corps.

This gives me his parents’ names (Malka and Jankiew Kalinsky) and where they were married— Tuszyn, near the Polish city of Lodz. And… click, click, click… I find them on someone else’s family tree, and there’s a long list of their children and all of them seem to have made it to America or London.

This was a lucky escape, because when the Nazis invaded, the Jews of Tuszyn were herded into the first ghetto created in Poland, and from there to Treblinka. Nothing remains of the community where my great-grandfather grew up, not even the cemetery, although if you click to Jewish history sites there are pictures of gravestones, possibly including those of my ancestors, broken up to use as steps on a flight of stairs.

I never knew my great-grandfather Isaac — even though, as it turns out, we overlapped in this world for 13 years. All my other great-grandparents died years before I was born. One was murdered at Auschwitz. Their lives always felt very remote to me, as did the world that they or their parents came from.

Before the internet, before the Iron Curtain fell, I grew up with not even a glimmer of expectation that one day I could find out anything about what happened to my family in the past. All I knew about Poland and Russia came from ancient children’s encylopaedias in which I read long histories of those countries. Perhaps this is where my feeling of inner Eastern European came from. The very idea that I might have known someone who could have told me about Jewish life in pre-war Poland is quite startling.

But I didn’t know Isaac, for the simple reason that he was not a good husband or father. In fact, the first time I knew his name was when I was pregnant, and my mother told me that I shouldn’t name a child, Isaac, because her grandfather was a bad man. The stories that lived after him were those of neglect and bad parenting. And the lessons that we learned were about the importance of women being able to earn a living and be independent of their husbands, should they need to be.

Researching our family trees can be painful and difficult for Jewish people. Our DNA is distinct, in part because we were so inter-married and inter-mingled, separated from others by our customs and their prejudice. And while that puts us in touch with the past, it could also be used against us in the future. As my brother said: “Now they can find out how Jewish we are by making us spit into a bowl? That’s not frightening at all.”