Wednesday 12 December 2018

Out of Our Neanderthal Trees

Original Neanderthal skull. Photo Don Hitchcock,
Family history research has come a long way since I began looking into my own ancestry in 1978. In those days the only resources accessible were parish registers in records offices or microfilm copies in large libraries. Today there’s the internet and many records are reproduced online. Family history research has never been so easy - or so easy to get wrong. Too many inexperienced researchers rely on false information that other inexperienced researchers assume to be correct rather than look for themselves.

One innovation of the 20th century is becoming increasingly popular – DNA testing. People can now discover where their ancestors were living before there were written records. DNA has also helped to identify new species of prehistoric human, or hominid. Before DNA the most well-known ancient hominid was Neanderthal Man, and in recent years Neanderthal DNA has been found in us. This has led to the obvious conclusion that our early ancestors interbred with Neanderthals.

While it’s something that is still being researched we should give a nod to the openly bisexual Swedish scientist who was the first to reconstruct the Neanderthal genome. His name is Dr. Svante Pääbo (b.1955).

In his book “Neanderthal Man: In Search of Lost Genomes” Svante chronicles the long search for Neanderthal DNA. He includes events in his personal life that occurred along the way, making it a sort of autobiography. A handful of references mention his sexuality and falling for the wife of a colleague and eventually marrying her.

Whether genetics influences a person’s choice of career in doubtful, but Svante has the right scientific family background to become a geneticist. His father was Sune Bergstrom, who won the Nobel Prize for Physiology/Medicine in 1982. His mother was Karin Pääbo, an Estonian chemist.

Svante studied medicine and biochemistry at Uppsala University, helping research into human DNA and the immune system and the effects of diseases, not unlike the HIV research being carried out by Dr. Devin Sok. But it wasn’t medicine and biochemistry that took Svante to Uppsala. It was archaeology. It was after two summers of unexciting excavation work that he decided on a change of subject. Inspired by his father he turned to medicine.

With the intention of becoming a medical practitioner Svante joined the lab of a professor who had been leading the way in cloning DNA of molecules in immune cells. His doctoral theses was on the subject. Yet throughout his work Svante retained his life-long interest in archaeology, particularly Ancient Egypt, and one thought struck him – could DNA survive in ancient Egyptian mummies?

Spurred on by this thought Svante rummaged through libraries and academic journals to find out if anyone had found ancient DNA. They hadn’t. So, like a red rag to a bull, Svante set off on a hunt for an Egyptian mummy. He obtained several pieces at a museum in Communist East Berlin and took them back to Uppsala.

With some excitement Svante discovered enough DNA to offer science the possibility of reproducing a whole ancient Egyptian genome in the future. He published his results in 1985. By being the first to publish research into pre-modern DNA Dr. Svante Pääbo had “invented” the science of palaeogenetics.

In 1990, with his own lab and professorial position in Munich, Svante embarked on the search for even older human DNA. By this time other scientists had joined the hunt. Some even went further and looked for DNA in prehistoric insects trapped in amber millions of years ago. If you’re a fan of “Jurassic Park” thank Svante Pääbo for kickstarting the whole dinosaur DNA thing (not that he approves of the idea himself).

In 1991 Svante “met” someone I wrote about several years ago, Ötzi the Iceman. Unsure of how old Ötzi was – did he die 100 yeas ago of 1,000? – Svante’s lab was asked to sample the Iceman’s DNA. They discovered that Ötzi’s DNA confirmed suspicions based on the object found with his body that he lived over 5,000 years ago.

Finding Neanderthal DNA was the next step. The first Neanderthal bones were discovered in 1856. They belonged a new Homo species and evolved from a common ancestor to us – Homo sapiens sapiens – about half a million years ago. The Neanderthals became extinct about 30,000 years ago. Svante was actually allowed to test a sample from one of those first Neanderthal bones, such was his reputation in this field of work. Headlines appeared around the world when the news was released in 1997 that DNA had been successfully extracted from a Neanderthal bone.

Nine years later Svante was ready to replicate the genome of a Neanderthal. I followed the story at the time, palaeontology being one of my other interests, so I was very pleased to find in my files the article (below) which proclaimed that Svante had successfully reproduced a Neanderthal genome in 2009.

What took Svante and geneticists by surprise was that 2% on European and Asian DNA contains Neanderthal-specific genes. In Svante’s words “Neanderthals were not totally extinct”.

But Svante’s work hasn’t stopped there. His team were asked to test a finger bone that had been discovered in the Denisova Cave in Siberia. It turned out to be a previously unknown Homo species that was named Homo denisova. It showed that three human species – sapiens (us), Neanderthals and Denisovans – co-existed in Siberia 30,000 years ago. Further research found that Denisovan DNA survives in 5% of human DNA in people in the area between Burma and northern Australia.

Svante Pääbo’s pioneering palaeogenetic research has led to a new understanding of human origins. It now seems that some early humans who migrated out of Africa interbred with Neanderthals of eastern Europe, and with Denisovans in central Asia, passing parts of their DNA down to you, me and almost everybody with European-South Asian ancestry.

One intriguing future direction for palaeogenetics is research for a cure for HIV. The Neanderthal and Denisovan DNA in humans carries left-overs genes from ancient viral infections. About 90% of all DNA, even ours, is “junk” – it isn’t used to produce anything, it just sits there in the genome waiting to be passed on to the next generation.

Those ancient viral remains are part of this “junk”, However, they belong to the same virus family as cancer and HIV. Very occasionally several pieces of junk-virus combine to produce cells which in turn produce cancer cells. Some HIV patients have a higher risk of developing cancer, for reasons that was not fully understood. Perhaps the answer is in their genes. Perhaps a way of totally deactivating the junk-virus DNA will lead to a treatment to slow down the development of cancer.

So we have come full circle. Svante Pääbo began his scientific career researching into viruses and their effects on the human immune system, and because of his pioneering palaeogenetic research scientists can now look at ancient Neanderthal DNA to discover a treatment for HIV and cancer patients.

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