Lisa Matisoo-Smith: We're all one family under the skin

Kiwi scientists first recognised the power of mitochondrial DNA to trace back humans' ancestry, to one woman who lived around 200,000 years ago in Africa. Photo / Supplied

Hate-driven events like yesterday’s Paris killings all more reason to reflect on our past, writes Lisa Matisoo-Smith

With recent events in the United States, Pakistan, Syria and Sydney, it may seem that hatred, religious intolerance and bigotry are taking over. Perhaps it's time to reflect on human history and consider something important given to you by your mother - not her wisdom, which no doubt could also help at times like these, but her mitochondrial DNA.

In 1987, New Zealand-born scientist Allan Wilson and his PhD students, Rebecca Cann and Mark Stoneking, published an extraordinary paper reporting that all modern humans can be traced back to a common female ancestor who lived in Africa some 200,000 years ago. The expansion of people out of Africa began only 60,000 years ago.

This means that most of the cultural, linguistic and physical variation we see in humans today has happened in that 60,000 years: humans occupied and adapted to all possible environments, from the Arctic Circle to the south coast of Australia, the Himalayas to the atolls of the Pacific. The settlement of Aotearoa, just 750 years ago, was the last step in the great human journey, from Africa to Aotearoa and everywhere in between in 60,000 years.

Allan Wilson recognised the power of the molecule called mitochondrial DNA for tracing human history. Unlike nuclear DNA -- the DNA that makes up your chromosomes, which you inherited from both of your parents and which mixes to form a unique combination that makes you -- your mitochondrial DNA (mtDNA) is passed down to you as an exact copy from your mother.

She inherited it from her mother, who inherited it from her mother and so on.

Every so often, a mutation occurs and one letter in that sequence of 16,500 letters that make up the mitochondrial genome changes and this new sequence is passed down through the generations. By comparing the sequence of mtDNA from people around the world, we can draw our family tree -- a tree that links all modern humans to that ancestral lineage that existed in Africa 200,000 years ago. This common maternal ancestor is often dubbed the mitochondrial Eve.

For the last 18 months I have been meeting New Zealanders across the country, taking cheek swabs that provide a sample of cells from which we can obtain mitochondrial DNA. The goal of the project, called The Longest Journey: From Africa to Aotearoa, is to identify the genetic ancestry of New Zealanders.

We all, either recently or through our ancestors, made the long trip that resulted in our being here in Aotearoa. We can trace those migration pathways through our mtDNA. I've collected random samples from Auckland, Hamilton, Wellington, Christchurch and Dunedin. I have also worked with various ethnic groups, from the Lebanese community in Dunedin to the Dalmatian community in Auckland. It's been a privilege to meet so many Kiwis, to hear their stories and see the amazing diversity present in Aotearoa.

You can't look at someone and guess their mtDNA haplotype (maternal lineage). As it turns out, we have almost every major branch on the mitochondrial tree represented among our population.

While our main interest is understanding deep history, our migration history covering many thousands of years, we're also asking about participants' recent family history. It saddens me how many people don't know their basic family history -- where their mum was born or their mum's mum. Many can phone a family member to find out. Unfortunately, many cannot.

During this holiday period, you might be spending time with family. Talk to them, ask the older generations about their lives, their stories. Record that family information before it is lost. While we can always track our ancient history through our mtDNA, we won't ever get those more recent stories back once they are forgotten. They are precious and part of your personal and our national identity.

With recent events that seem to draw attention to and be motivated by human differences, perhaps it would do us some good to consider our recent shared ancestry and the amazing human history that has seen us spread across the globe.

New Zealand is not the perfect society, but we do have much to be thankful for. We have not been faced with these recent acts of hatred that might drive retaliation. We're in a position right now to decide to act in ways that will continue to make New Zealand a unique, diverse and relatively safe place to live, where everyone is welcome and will not live in fear of persecution because of their colour or place of worship.

Let us think about our common ancestry while we celebrate our own family histories and traditions.

• Professor Lisa Matisoo-Smith is principal investigator at the University of Otago's Allan Wilson Centre.