Horizon Magazine – Page 2 – More Than A Dodo

How we got bigger, more vulnerable brains

This article is taken from European research magazine Horizon as part of our partnership to share natural environment science stories with readers of More than a Dodo. For more on the development of the brain see our Brain Diaries exhibition site.

One of the major features that distinguishes 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 Australopithecines. During 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…

This year, the mystery was partially solved by Professor Pierre Vanderhaeghen 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.

Scientists 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.

His lab discovered 35 hominid – present only in apes and humans – genes that were active in foetal brain tissue. They then became intrigued by three specific genes – 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.

This error created entirely new proteins which likely helped our ancestors’ 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’ extinct cousins – the Neanderthals and Denisovans.

(The NOTCH 2NL) genes are only present in humans today. They were also present in Neanderthal DNA, but not in chimpanzees
Prof. Vanderhaeghen

Evolution
These genes control the growth rate and differentiation of brain stem cells – the starter cells that multiply and give rise to all neurons in our brain – 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’s descendants – including Neanderthals, Denisovans, and modern humans.

Prof. Vanderhaeghen’s 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. 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.

As 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. “Patients 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,” he said.

Prof. Vanderhaeghen is now studying some 20 of the remaining human-only genes to see how they contributed to the evolution of the human brain.

Something like 40-50% of the Neanderthal genome can still be found in people today.
Prof. Svante Pääbo, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany

The 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.

In the last decade, however, scientists have begun to look at the DNA inside these bones. Professor Svante Pääbo, 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.

This 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 – our own species appears to have interbred with some of these ancient relatives during our history.

Ancient humans
Scientists 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.

An international consortium of researchers is sequencing the 3 billion bases that make up the genome of our closest relative – the Neanderthal. The sequence is generated from DNA extracted from three Croatian Neanderthal fossils using novel methods developed for this project. Image credit – Frank Vinken for Max Planck Society

“Different people tend to carry different pieces of the Neanderthal genome,” said Prof. Pääbo, who is undertaking a project called 100 Archaic Genomes to decipher the DNA of ancient human individuals. “Something like 40-50% of the Neanderthal genome can still be found in people today,” he said.

According to Prof. Pääbo, we retained some of this DNA because it offered an advantage to our ancestors. “Some (of this retained DNA) has to do with the immune system, presumably helping us to fight off infectious diseases.”

The power of genetics to unravel the history of human evolution took a new twist in 2010 after Prof. Pääbo’s lab sequenced DNA from a finger bone fragment found by a Russian archaeological team in a remote Siberian cave.

The 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.

Last year, Prof. Pääbo’s 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.

Denisovans left a more impressive stamp on some of us than Neanderthals, according to Prof Pääbo. 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.

Prof. Pääbo and his colleagues will soon publish their third high-quality genome – where almost the entire DNA sequence is intact – 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 – 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. Pääbo.

“There may even be other forms of extinct humans out there to be discovered by studying the DNA of the (ancient) bones we find,” he said.

Top image: The skull of a Australopithecus sediba, a species of Australopithecines, who were our ancestors and whose brains started to grow two to three million years ago. Image credit – Australopithecus sediba by Brett Eloff, courtesy Profberger and Wits University is licensed under CC BY-SA 4.0.

This post Genetic error led humans to evolve bigger, but more vulnerable, brains was originally published on Horizon: the EU Research & Innovation magazine | European Commission.

Decoding the honeybee dance

This article is taken from European research magazine Horizon as part of our partnership to share natural environment science stories with readers of More than a Dodo.

Unravelling one of the most elaborate forms of non-human communication – the honeybee’s waggle dance – could help researchers better understand insect brains and make farming more environmentally friendly.

It’s part of a field of work looking at insect neurology which is helping to unravel the complexity of their brains.

Bees have evolved a unique, and ingenious, way to communicate with each other – the waggle dance. By shaking their abdomens in a particular way, a bee can tell others in its hive the specific direction and distance of a food source or a new site for a nest.

‘If nectar or pollen is in the direction of the sun, a bee will run a figure of eight that is orientated towards the top of the hive. If pollen is found 90 degrees from the sun they will point that way instead,’ explained Dr Elli Leadbeater, a bee expert from the School of Biological Sciences at the University of London, in the UK.

The longer the bees spend dancing corresponds to the better quality of a food source, while the more time spent on each figure eight represents the distance from the pollen or nectar.

Researchers now believe that decoding this information-packed dance further could reveal a link between bees’ brains and how the surrounding environment affects them. In a project called BeeDanceGap, Dr Leadbeater is working to identify the exact genes in the bee brain that play a role in helping the insects understand this waggle dance.

To do this, researchers must first identify the best dancing bees in a test hive and watch them as they reveal a food source to other worker bees. The newly educated bees are then captured as they leave the hive so their brain tissue can be genetically analysed to determine which genes associated with learning and memory were activated from following the waggle dance.

Only a few individuals are used in this way and the genetic data provides a deep insight into the neurology of a bee’s brain – at a time crucial to their future.

The observation bee hive at the Oxford University Museum of Natural History gives visitors a glimpse into hive life.

Collapse

Beekeepers around the world have reported that many of their bees leave and never come back, causing hives to suddenly collapse. Experts believe there are several factors contributing to this widespread loss of bee colonies, including climate change, parasites and habitat loss. Agrichemicals like pesticides and neonicotinoids, which are used to kill unwanted insects on farms, have also been strongly linked to the problem.

‘The rate pesticides or neonicotinoids are applied to crops don’t necessarily kill bees but they make them worse at foraging,’ said Dr Leadbeater.

If you do damage to just one part of the brain of a lot of individual bees, it can have huge consequences for the whole colony.
Dr Elli Leadbeater, University of London, UK

Neonicotinoid pesticides have been found to bind to parts in the insect brain, disrupting neural transmission. This leads to some brain cells either failing to develop or not functioning properly.

The EU recently banned neonicotinoids, which Dr Leadbeater believes is a huge step forward in protecting bees, but she said governments still need more rigorous ‘long-term environmental safety monitoring’. Without this, there is a risk that other agricultural products used in place of neonicotinoids could impact honeybees in a similar way.

But when the first results of BeeDanceGap are published later this year, they could contribute to building better criteria for testing future agriculture practices or products. Dr Leadbeater believes it will provide a new understanding of a bee’s brain, and so help identify problems sooner.

The impacts of quickly identifying problems go far further than just supporting beekeepers and their insect charges. Protecting honeybees, along with bumblebees and wild bees, is also essential to maintain a healthy and productive environment. These insects pollinate over 80% of crops and wild plants in Europe. According to Professor Martin Giurfa, from the Research Center on Animal Cognition at CNRS in France, ‘preserving little brains is about preserving biodiversity’.

More than machines

Honeybees have a higher social complexity than many other species. Alongside the waggle dance communication, each hive has a division of labour where different workers have responsibility for a variety of tasks – such as foraging for pollen, nursing the young, building hives and even removing the dead.

Prof. Giurfa is co-leading the BrainiAnt project, which looks at how this type of complex social behaviour evolved and how it affected the structure of insect brains. He said that when ‘you understand how bees perceive the world, it is easier to find ways to protect them’.

Through the work of researcher Dr Sara Arganda, the project is investigating a part of the insect brain called the mushroom body, where learning occurs and long-term memories are stored. Researchers analysed bee behaviour and gave them memory tests, such as navigating paths using colour cues, in order to learn more about the structure of insect brains.

The project strengthened the argument that bee brains are more complex than previously thought. ‘Most findings are saying that insects are more than simple machines, which comes from studies in the honeybee,’ said Prof. Giurfa. ‘(But) the entrance region of the mushroom body shows a level of complexity and the studies show that this complexity is not rigid, it is plastic.’

This means its structure is changing all the time, which mirrors how human brains work. ‘(Bee) brains are capable of sophisticated performances such as learning concepts and rules; they are incredible organs and they need to be defended,’ said Prof. Giurfa

To further advance understanding of the mushroom bodies and how they function in different species, the project is being co-led by Professor James Traniello at Boston University in the US, an expert in ant evolutionary neurobiology.

Ants, which are related to honeybees, have brains that may be 100 times smaller, and due to their minute size, provide insights into how insect brains are structured.

‘What happens to neural tissue at an extremely small size?’ asked Prof. Traniello. ‘Are you losing neurons, are neurons becoming more efficient in their actions, how many neurons do you have to string together to form a circuit that enables behaviours as complex as what you would see in ants? How does the collective intelligence of an ant colony impact the structure of the brain?’

If BrainiAnt can answer these questions, it would provide a clearer picture of the evolution and function of ant brains.

‘The next step is trying to understand the genes that are involved in regulating brain size, compartment variability, metabolism and other functions,’ said Prof. Traniello.

He added that a better understanding of neural tissue could also help to guide attempts to genetically engineer bees so their brains are resistant to environmental threats like neonicotinoids. Although far off, it could mean that bees, and the benefits they bring to the environment, will have a more secure future.

The research in this article was funded by the EU.

The issue

One in ten pollinating insects is on the verge of extinction, and a third of bee and butterfly species are in decline.

On 1 June, the European Commission launched a proposal to tackle this problem at an EU level. It includes a new monitoring process to collect quality data and identify trends, action plans to protect insect habitats and incentives for businesses such as those in the agrifood sector, to contribute to conservation.

The proposal, known as the EU Pollinators Initiative, has a number of short-term actions to be taken before 2020, at which point the progress will be reviewed.

This post Decoding the honeybee dance could lead to healthier hives was originally published on Horizon: the EU Research & Innovation magazine | European Commission.