[{"command":"openDialog","selector":"#drupal-modal","settings":null,"data":"\u003Cdiv id=\u0022republish_modal_form\u0022\u003E\u003Cform class=\u0022modal-form-example-modal-form ecl-form\u0022 data-drupal-selector=\u0022modal-form-example-modal-form\u0022 action=\u0022\/en\/article\/modal\/6902\u0022 method=\u0022post\u0022 id=\u0022modal-form-example-modal-form\u0022 accept-charset=\u0022UTF-8\u0022\u003E\u003Cp\u003EHorizon articles can be republished for free under the Creative Commons Attribution 4.0 International (CC BY 4.0) licence.\u003C\/p\u003E\n \u003Cp\u003EYou must give appropriate credit. We ask you to do this by:\u003Cbr \/\u003E\n 1) Using the original journalist\u0027s byline\u003Cbr \/\u003E\n 2) Linking back to our original story\u003Cbr \/\u003E\n 3) Using the following text in the footer: This article was originally published in \u003Ca href=\u0027#\u0027\u003EHorizon, the EU Research and Innovation magazine\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003ESee our full republication guidelines \u003Ca href=\u0027\/horizon-magazine\/republish-our-stories\u0027\u003Ehere\u003C\/a\u003E\u003C\/p\u003E\n \u003Cp\u003EHTML for this article, including the attribution and page view counter, is below:\u003C\/p\u003E\u003Cdiv class=\u0022js-form-item form-item js-form-type-textarea form-item-body-content js-form-item-body-content ecl-form-group ecl-form-group--text-area form-no-label ecl-u-mv-m\u0022\u003E\n \n\u003Cdiv\u003E\n \u003Ctextarea data-drupal-selector=\u0022edit-body-content\u0022 aria-describedby=\u0022edit-body-content--description\u0022 id=\u0022edit-body-content\u0022 name=\u0022body_content\u0022 rows=\u00225\u0022 cols=\u002260\u0022 class=\u0022form-textarea ecl-text-area\u0022\u003E\u003Ch2\u003EGenetic error led humans to evolve bigger, but more vulnerable, brains\u003C\/h2\u003E\u003Cp\u003EOne of the major features that distinguish humans from other primates is the size of our brains, which underwent rapid evolution from about two to three million years ago in a group of our ancestors in Africa called the \u003Cem\u003EAustralopithecines. \u003C\/em\u003EDuring this period, the human brain grew almost three-fold to reach its current size. Scientists know this from skull remains, but have puzzled over how it happened.\u003C\/p\u003E\u003Cp\u003EThis year, the mystery was partially solved by Professor \u003Ca href=\u0022http:\/\/www.vib.be\/en\/research\/scientists\/Pages\/Pierre-Vanderhaeghen-Lab.aspx\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003EPierre Vanderhaeghen\u003C\/a\u003E at the Flanders Institute for Biotechnology in Belgium. Prof. Vanderhaeghen, who was conducting his work as part of the GENDEVOCORTEX project, went on a hunt for the genes that drove the growth of human brains.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EScientists had suspected that brain expansion began in our human ancestors when they evolved genes that are switched on in the foetus, when a lot of key brain development occurs. Prof. Vanderhaeghen therefore looked for genes present in human foetal tissue, but missing from our closest living relatives, apes.\u003C\/p\u003E\u003Cp\u003EHis lab discovered \u003Ca href=\u0022https:\/\/linkinghub.elsevier.com\/retrieve\/pii\/S0092867418303994\u0022 target=\u0022_blank\u0022 rel=\u0022noopener noreferrer\u0022\u003E35 hominid - present only in apes and humans - genes \u003C\/a\u003Ethat were active in foetal brain tissue. They then became intrigued by three specific genes \u2013 all similar to NOTCH genes, an ancient gene family involved in sending messages between cells and that are present in all animals. They found that the three new genes, collectively named NOTCH 2NL, were created by a copy and paste error of an original NOTCH gene.\u003C\/p\u003E\u003Cp\u003EThis error created entirely new proteins which likely helped our ancestors\u0027 cerebral cortex to balloon. This is the part of our brain responsible for our language, imagination and problem-solving abilities. Scientists at the University of California, Santa Cruz, have also identified the NOTCH 2NL genes in DNA from Homo sapiens\u2019 extinct cousins - the Neanderthals and Denisovans.\u003C\/p\u003E\u003Cp\u003E\u2018(The NOTCH 2NL) genes are only present in humans today. They were also present in Neanderthal DNA, but not in chimpanzees,\u2019 Prof. Vanderhaeghen said.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EEvolution\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EThese genes control the growth rate and differentiation of brain stem cells \u2013 the starter cells that multiply and give rise to all neurons in our brain \u2013 causing them to seed more nerve cells, which in turn helped to expand brain size. The genes likely led to more neurons and brain tissue in our ancestor\u2019s descendants \u2013 including Neanderthals, Denisovans, and modern humans.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EProf. Vanderhaeghen\u2019s research could also help to provide new insights into brain disorders. The US researchers linked genetic faults in DNA that were very similar to NOTCH 2NL, to children born with enlarged brains or small brains.\u0026nbsp;Many of the new human-specific genes are located in a small area of our genome that plays an important role in brain size, according to Prof. Vanderhaeghen.\u003C\/p\u003E\u003Cp\u003EAs DNA in this area closely resembles another part of the genome where it was originally cut and pasted from millions of years ago, errors are more likely, said Prof. Vanderhaeghen. \u2018Patients who have (inherited) deletions in this area tend to be at risk of developing schizophrenia, whereas patients with duplications are more at risk of autistic spectrum disorder,\u2019 he said.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EProf. Vanderhaeghen is now studying some 20 of the remaining human-only genes to see how they contributed to the evolution of the human brain.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u003Cblockquote class=\u0022tw-text-center tw-text-blue tw-font-bold tw-text-2xl lg:tw-w-1\/2 tw-border-2 tw-border-blue tw-p-12 tw-my-8 lg:tw-m-12 lg:tw--ml-16 tw-float-left\u0022\u003E\n \u003Cspan class=\u0022tw-text-5xl tw-rotate-180\u0022\u003E\u201c\u003C\/span\u003E\n \u003Cp class=\u0022tw-font-serif tw-italic\u0022\u003E\u2018Something like 40-50% of the Neanderthal genome can still be found in people today.\u2019\u003C\/p\u003E\n \u003Cfooter\u003E\n \u003Ccite class=\u0022tw-not-italic tw-font-normal tw-text-sm tw-text-black\u0022\u003EProf. Svante P\u00e4\u00e4bo, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany\u003C\/cite\u003E\n \u003C\/footer\u003E\n\u003C\/blockquote\u003E\n\u003C\/p\u003E\u003Cp\u003EThe use of genetics to study human evolution in this way is helping to transform our understanding of how our own species compared to our ancestors. Traditionally, scientists have studied extinct species by looking at the fossilised remains of their bones. This was how they discovered the existence of Neanderthals, the extinct human species that lived across Europe and much of Asia before vanishing around 40,000 years ago.\u003C\/p\u003E\u003Cp\u003EIn the last decade, however, scientists have begun to look at the DNA inside these bones. Professor Svante P\u00e4\u00e4bo, director of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, has led the way in sequencing DNA of these extinct humans from small bone fragments.\u003C\/p\u003E\u003Cp\u003EThis allows scientists to compare modern human DNA with that of extinct humans, rather than just living relatives like chimps. Already, the work has revealed some surprising findings \u2013 our own species appears to have interbred with some of these ancient relatives during our history.\u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EAncient humans\u003C\/strong\u003E\u003C\/p\u003E\u003Cp\u003EScientists have found that the DNA of every person outside Africa is 1-2% Neanderthal, meaning that these extinct human relatives had offspring with our own ancestors.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003E\u003Cfigure role=\u0022group\u0022 class=\u0022@alignleft@\u0022\u003E\n\u003Cimg alt=\u0022That many people still retain Neanderthal DNA today could mean that it plays a role in our immune system. Image credit - Frank Vinken for Max Planck Society\u0022 height=\u0022799\u0022 src=\u0022https:\/\/horizon-magazine.eu\/research-and-innovation\/sites\/default\/files\/hm\/MPI_L_EVA_body.jpg\u0022 title=\u0022That many people still retain Neanderthal DNA today could mean that it plays a role in our immune system. Image credit - Frank Vinken for Max Planck Society\u0022 width=\u00221200\u0022\u003E\n\u003Cfigcaption class=\u0022tw-italic tw-mb-4\u0022\u003EThat many people still retain Neanderthal DNA today could mean that it plays a role in our immune system. Image credit - Frank Vinken for Max Planck Society\u003C\/figcaption\u003E\n\u003C\/figure\u003E\n\u003C\/p\u003E\u003Cp\u003E\u2018Different people tend to carry different pieces of the Neanderthal genome,\u2019 said Prof. P\u00e4\u00e4bo, who is undertaking a project called 100 Archaic Genomes to decipher the DNA of ancient human individuals.\u003C\/p\u003E\u003Cp\u003E\u2018Something like 40-50% of the Neanderthal genome can still be found in people today,\u2019 he said.\u003C\/p\u003E\u003Cp\u003EAccording to Prof. P\u00e4\u00e4bo, we retained some of this DNA because it offered an advantage to our ancestors. \u2018Some (of this retained DNA) has to do with the immune system, presumably helping us to fight off infectious diseases.\u2019\u003C\/p\u003E\u003Cp\u003EThe power of genetics to unravel the history of human evolution took a new twist in 2010 after Prof. P\u00e4\u00e4bo\u2019s lab sequenced DNA from a finger bone fragment found by a Russian archaeological team in a remote Siberian cave.\u003C\/p\u003E\u003Cp\u003EThe analysis revealed the bone belonged to a previously unknown human relative, now called Denisovans after Denisova Cave where the bone was found. This mysterious ancient human species lived at around the same time as Neanderthals, but further east into Asia.\u003C\/p\u003E\u003Cp\u003ELast year, Prof. P\u00e4\u00e4bo\u2019s group published DNA sequences from a tooth found in the cave - the fourth ever Denisovan discovered. We now know Denisovan DNA carries more variation than Neanderthal DNA, leading scientists to conclude that they were more widespread than the better-known Neanderthals.\u0026nbsp;\u003C\/p\u003E\u003Cp\u003EDenisovans left a more impressive stamp on some of us than Neanderthals, according to Prof P\u00e4\u00e4bo. Their DNA can be found in people across Asia today, while indigenous peoples of Papua New Guinea and Australia may carry up to 5%. Tibetans also carry some Denisovan DNA in their genomes, which has helped them adapt to life at high altitudes where there is little oxygen in the atmosphere.\u003C\/p\u003E\u003Cp\u003EProf. P\u00e4\u00e4bo and his colleagues will soon publish their third high-quality genome \u2013 where almost the entire DNA sequence is intact \u2013 of a Neanderthal from Siberia. A deciphered genome of this quality allows for better DNA comparisons and could tell us more about the evolution of important genes \u2013 such as those linked to the development and function of the brain. It will add yet another puzzle piece to help us understand the history of our closest extinct relatives, according to Prof. P\u00e4\u00e4bo.\u003C\/p\u003E\u003Cp\u003E\u2018There may even be other forms of extinct humans out there to be discovered by studying the DNA of the (ancient) bones we find,\u2019 he said.\u003C\/p\u003E\u003Cp\u003E\u003Cem\u003EThe research in this article was funded by the European Research Council. 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