Glenda Lewis
Aotearoa was the final destination of a very long journey that began in Africa more than 65,000 years ago. Whether you’re a redheaded country music singer in Gore or a Filipino dairy worker in Dannevirke, your ancestral homeland is Africa.
When a small band of modern humans filtered out of Africa into Europe and Asia, they encountered other human types who had arrived there hundreds of thousands of years before. Our new breed of taller, seemingly more savvy and better equipped men and women co-existed with Neanderthals for at least 10,000 years before they died out, whether through force or happenstance.
Our common ancestor was Homo erectus. We were not yet so different from Neanderthals that we couldn’t interbreed. The encounters were rare and rarely productive but nevertheless, everyone today who is NOT of pure African descent carries a small percentage of Neanderthal DNA, about 2 per cent – slightly more in Asian populations who seem to have had additional, later encounters. Those Neanderthal jokes about our colleagues and former boyfriends have rebounded on us.
This genetic legacy has given us some good and bad traits, such as stronger hair and skin, a predisposition to type 2 diabetes and Crohn’s disease, and increased risk of nicotine addiction. Apparently Neanderthals shared our on/off faculty for appreciating the defining note of pinot noir and violets, a compound called beta ionine. A single nucleotide difference (a basic component of DNA) distinguishes the active and inactive version of the gene.
The first scientist to think of using differences in our DNA to trace our origins and relatedness grew up on a farm in Pukekohe.
The late, great NZ scientist, Allan Wilson, who should be a household name here, spent his adult life in America, based at the
Regardless of what we look like,
writes, our ancestral home was Africa.
University of California, Berkeley. He died in 1991 from leukaemia, aged 56. Wilson deduced that chimpanzees and the first human species diverged from a common ancestor only five to seven million years ago, not about 30m as previously thought – a bit too close for comfort for some.
It caused a bitter controversy at the time, and not just among evolution deniers. Scientists are human too, and not always objectively ‘‘sapiens’’. Reputations become nailed to old masts.
Wilson led a group of evolutionary biologists who realised that we could reconstruct human history by studying markers in our mitochondrial DNA (mtDNA), which is inherited lock, stock and barrel from mother, and not mixed up with father’s DNA when sperm meets egg. Every so often, a spelling mistake, known as a mutation, is made when the DNA is being copied. Once a mutation occurs, it is then passed on to all future generations.
These mtDNA mutations rarely have any effect on the person. Wilson and his team realised that if they looked at mtDNA from people around the world, they could compare the DNA and draw a family tree, identifying when and where these mutations occurred. The different mtDNA lineages could be used to trace the movement of populations across the globe.
They calculated that all humans alive today trace their origin back to one woman – socalled Mitochondrial Eve – who lived in Africa a mere 150,000 years ago. This doesn’t mean that she was the only woman on Earth at the time, but that all other lines have since become dead ends, literally.
The different branches of the mitochondrial family tree are labelled by letters, with each branch defined by a particular mutation or combination of mutations.
The oldest lineages are the L branches, which are found only in African populations. About 65,000 years ago, a small group of humans carrying the L3 lineage left Africa, probably through what is now Egypt. This group soon split and the mutations occurred that define the two main non-African lineages, the MandN branches. Women carrying the Nlineages gave rise to all European lineages, with the most common branches found in Western Europeans today being H, U, J, T, K, V, and X. These seven Western European maternal ancestors inspired the book The Seven Daughters of Eve by Bryan Sykes. He named these clan mothers Helena, Ursula, Jasmine, Tara, Katrine, Velda and Xenia.
While Helena, Ursula, Jasmine and the girls went north, some of our ancestors headed east and moved very quickly through southern Asia, towards the Pacific. They could walk through what is now Island Southeast Asia when ice ages locked up massive volumes of water and sea levels fell. Recent research suggests that they arrived in Australia and New Guinea, which were joined in a super-continent called Sahul, as early as 60-65,000 years ago. Aboriginal Australians and Papuans have been geographically and genetically isolated for a very long time. It was a one-way journey for them. These people carried mtDNA lineages belonging to the Mbranch, as well as some N lineages.
On those early forays into Asia, it seems we also interbred with another group of long-separate Homo erectus descendants called Denisovans, after the cave in Siberia where the relics of these people were miraculously discovered – part of the finger-bone of a small girl and a few teeth – amidst tonnes of rock and dirt. These treasured remains were so well preserved that scientists were able to sequence the entire genome (the complete set of an organism’s DNA). Those first modern humans who travelled through Asia clearly ran into Denisovans on the way. Their descendants today, including Aboriginal Australians