The ideas of belonging and identity are at the very core of what it means to be human, but those themes become much more complex when the person in question is adopted. The adopted person’s search for their biological parents is a familiar narrative, but also one fraught with emotional dangers and complications, and it’s a journey that is given new insight in Jackie Kay’s remarkable new book.

Red Dust Road, subtitled ‘An Autobiographical Journey’, is the poet and novelist’s account of the search for her biological parents and it is, typically for Kay’s writing, full of passion, intelligence and a healthy dose of self-deprecating humour. Kay was born in Edinburgh to a Scottish Highland mother and a Nigerian father, and given up for adoption as a baby. Her adoptive parents, two card-carrying members of the Communist Party, brought her up in Glasgow where, thanks to her skin colour, she always felt like she was an outsider.

Despite a childhood she describes as full of love, Kay always had a lingering emptiness inside, the knowledge that her parents had given her away gnawing away at her a little. ‘I’ve spoken to a lot of adopted people and many of them have that sense of emptiness,’ she says. ‘I think at some very deep level the knowledge that you’ve been given up for adoption as a baby, that your original parents shipped you out, it’s almost an existential thing to deal with. Although all of us are alone in our various different ways, the state of being adopted can make you feel even more alone, even when you’ve got wonderful parents. That’s the contradiction.’

That contradiction did not lead to a particularly happy state of mind for Kay, who confesses in the book to terrible feelings of guilt about wanting to know more about her biological origins. ‘I couldn’t have wished for a better upbringing,’ she says. ‘My parents were much better than a lot of people’s biological parents, so when I started looking for my biological parents, I felt as if I was almost being adulterous. It feels disloyal at a very deep level.’

The initial trigger that set Kay off on her journey was when she became pregnant with her son, making her wonder about the woman who had carried her. When she tracked her down, her birth mother was clearly suffering from the early stages of Alzheimer’s, leading to frustration and distress on both sides of the meeting. For Kay, this fracturing of memory was absolutely key to her thinking about identity.

‘To me the book is really about memory,’ she says. ‘It’s about how our memories form us, and how the lack of them disrupts us, so when they start to break down like with Alzheimer’s, people literally lose themselves, because they lose the ability to remember. We’re actually made of memories as much as flesh and blood, we’re made of memories and myths and stories, and that’s our way of affirming ourselves and that’s what makes us different from other species.’

Interestingly, Kay decided to mirror this non-linear idea of memory in Red Dust Road within its structure, which is a strange but oddly moving mosaic of passages, written in different registers from different points of view, and out of chronological sequence. ‘Memories are about finding a way of structuring our lives and they show us that our lives are not linear or chronological particularly. One memory might trigger another and yet those things might be years apart, which is why I structured the book the way I did, because we do move in a back-and-forth way, that’s how our mind and memory work.’

One of the upshots of this approach is that the book opens with a marvellous scene in which Kay meets her Nigerian father for the first time in a hotel in Abuja, something that happened several years after Kay had already tracked down her birth mother. To say her birth father is larger than life would be an understatement, as he spends several hours in her hotel room dancing and singing around her in an attempt to rid her of the sin of being born out of wedlock. Kay’s account of this is hilarious but also deeply poignant, like much of the book. ‘He is a real character, you couldn’t make him up,’ she laughs. ‘I’m so glad I met him, but it is bizarre having someone dance and clap around you and try to cleanse you of your sin, and that’s your father. Him being so prurient about my lesbianism as well, asking all these questions about what lesbians did in bed, that was very strange too.’

Kay has skirted around these issues of identity and belonging throughout her esteemed career, ever since her debut poetry collection, The Adoption Papers, was published almost 20 years ago. Through award-winning novels and stories, acclaimed radio and stage plays, it feels like she has been slowly feeling her way towards this book over the years. ‘I feel almost like I’ve lived my life to write this book, that my life has been this book, and the two things are interchangeable. I couldn’t have written it 20 years ago, even if I’d found my parents back then. You have to have a way of looking at things that feels like you’re inside it but also outside it.’

Jackie Kay, 25 Aug, 8pm, £10 (£8).