First humans to reach Aotearoa
DNA evidence shows the founding population of Aotearoa must have numbered in the hundreds, Glenda Lewis reports in the second and final article on human migration to this land.
Last week we explained how some of the DNA we inherit from our mothers enables us to trace the journeys of our ancestors out of Africa. This clever reverse tracking, comparing the DNA from living people and fossils, was the brainchild of New Zealand scientist Allan Wilson.
To recap: everyone inherits a small loop of DNA from their mother, which is not combined with father’s DNA when the sperm fertilises the egg. It sits outside the cell nucleus where all our other DNA resides. This DNA is contained in, and is the work-plan for, our mitochondria, which are self-contained spherical units that generate the energy to drive cell functions.
Occasionally, on average once every 100 generations, there is a mutation in this mitochondrial DNA (mtDNA). Once a mutation occurs, it is passed on to all future generations of that woman’s children and thus acts as an ancestral sign post. These changes enable evolutionary biologists to trace our maternal line very accurately, going right back to our common origins in Africa.
Maternal lineages, characterised by these mutations, are labelled by alternating letters and numbers. All non-Africans descend from one maternal lineage (L3) that left Africa about 65,000 years ago. Each time a mutation that is shared by a large number of people is identified, the branch on the human family tree splits and is given a number. So the B branch may split into four branches – B1, B 2, B 3 and B 4.
Then when those branches split, the new lineages, or subbranches, are given letters, so B4 splits into B4a and B4b and so on. The next level splits are numbered – B4a1, B4a2 etc, then B4a1a, B4a1a1, B4a1a1. These specific subbranches, with their letter and number designations, are called haplogroups, and are like a postcode designation of where your mtDNA sits on the growing human family tree.
Most Polynesians, including Ma¯ ori, have mtDNA that belongs to the B4a1a branches. No Ma¯ orispecific mtDNA lineages have been identified, as all of the lineages identified in Ma¯ ori are also found in other Polynesian populations, which is to be expected given the timing and history of settlement.
The mutations that define the B branch of the mtDNA family tree first occurred between 40,000 and 50,000 years ago in Asia. About a third of indigenous Americans are also of the B lineage, but are on the B2 branch. Their ancestors migrated from Asia to America before the land bridge disappeared at the end of the last Ice Age, about 10,000 years ago. People carrying the B4a1a lineages spread down through island Southeast Asia and eastward into the Pacific.
These early island dwellers are known as the Lapita people, identified by remains of their pottery which has distinctive patterns of indentation. Lapita sites first appear around the Bismarck Archipelago (New Guinea) about 3350 years ago, and the Lapita were the first people to settle Vanuatu, New Caledonia, Fiji, Tonga and Samoa, about 3000 years ago.
It was another 2000 years before the next big push into Central and East Polynesia, journeys of several thousand kilometres. These bold voyagers sailed east against the prevailing winds which means that these journeys were probably deliberate explorations and not random excursions. That they found tiny, vastly separated places such as Hawaii and Easter Island is a testament to their sailing and navigational skills.
Even Captain Cook was impressed, and he knew what was involved. ‘‘How shall we account for this nation spreading itself over so vast an ocean?’’ he wondered. Cook noted how very similar all the island languages were – an indication of very recent separation.
Language evolution is a proxy for human DNA changes and migration. Tupaia, the highranking priest Cook took with him in 1769 when he left Tahiti, was able to communicate with Ma¯ ori in Uawa/Tolaga Bay on the East Coast. They may never have been allowed onshore otherwise. Our islands were the last to be discovered – the end of a 65,000-year diaspora by humans, who used their creative ingenuity to adapt to any habitat, from Siberia to the American deserts.
In excavations undertaken from the 1930s through the 1960s, the remains of a significant village site were discovered at Wairau Bar, near Blenheim. More than 45 burials were found and these were some of the earliest human remains found in New Zealand.
While the site has been radiocarbon-dated to the early 1300s, its age could also be deduced from of the thousands of moa and other bird, fish and sea mammal bones. Moa went extinct within 100 years of humans arriving. The people of Wairau Bar were among the first inhabitants of Aotearoa.
Examination of their DNA, which continues in the ancient DNA lab at University of Otago, combined with that of modern Ma¯ ori, shows such variety in the maternal genetic inheritance that lead investigator, Professor Lisa Matisoo-Smith, has deduced that the founding population of Aotearoa must have numbered in the hundreds, much larger than previously thought. It’s possible that scouts found this promising new land, After, there was a deliberate mass migration, likely from more than one island. Significantly, the man-made objects found with the burials at Wairau Bar are similar to artefacts from the Cook, Society and Marquesas islands in East Polynesia.
The linguistic similarities, DNA data and oral traditions of this region also strongly suggest that it is the Hawaiiki or homeland of the founding waka. When people in the Pacific migrated to new islands, they took their important plants and animals with them – sweet potatoes, dogs, pigs, chickens and rats (kiore, which are different from European rats).
Matisoo-Smith studies the DNA of these animals and plants and compares it with human DNA information to work out migration pathways.
A big question has always been: did Pasifika people reach South America, and was there any comingling of those populations? The DNA of chicken bones and the mere presence of the kumara – a South American native – in early Polynesian sites, indicate that they did make it that far.
To date, there is no evidence of any human inter-breeding from those early encounters, so perhaps they were just quick recces or trading missions. Or maybe they got a hostile reception.
The arrival of Europeans in Aotearoa in the 18th century connected two long-separate branches of the human family tree. Commonly, most Ma¯ ori men today carry Y-chromosomes of European descent, and Pacific maternal lineages. In other words, the sailors, whalers and missionaries readily mated with Ma¯ ori women. Thus, the people who went their different ways somewhere in the Middle East 60,000 years ago, came together again in Aotearoa.
What is left to know and what can we know? Conceivably, we will soon know our relationship with every other human being. But how important is it to know that you have a 10th cousin in Boise, Idaho? Just 10 generations back, our individual family tree encompasses hundreds, if not thousands, of relatives.
The human family tree is a dense thicket. In fact, we are all closely related and share a maternal ancestor who lived in Africa about 150,000 years ago. If only that knowledge had more power. ❚ Information and research provided by Professor Lisa Matisoo-Smith FRSNZ, University of Otago