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Nancy Lane awarded Doctorate of Science by Heriot-Watt University

From Department of Zoology. Published on Nov 23, 2015.

‘Fourth strand’ of European ancestry originated with hunter-gatherers isolated by Ice Age

By fpjl2 from University of Cambridge - Department of Zoology. Published on Nov 16, 2015.

The first sequencing of ancient genomes extracted from human remains that date back to the Late Upper Palaeolithic period over 13,000 years ago has revealed a previously unknown “fourth strand” of ancient European ancestry.

This new lineage stems from populations of hunter-gatherers that split from western hunter-gatherers shortly after the ‘out of Africa’ expansion some 45,000 years ago and went on to settle in the Caucasus region, where southern Russia meets Georgia today.

Here these hunter-gatherers largely remained for millennia, becoming increasingly isolated as the Ice Age culminated in the last ‘Glacial Maximum’ some 25,000 years ago, which they weathered in the relative shelter of the Caucasus mountains until eventual thawing allowed movement and brought them into contact with other populations, likely from further east.

This led to a genetic mixture that resulted in the Yamnaya culture: horse-borne Steppe herders that swept into Western Europe around 5,000 years ago, arguably heralding the start of the Bronze Age and bringing with them metallurgy and animal herding skills, along with the Caucasus hunter-gatherer strand of ancestral DNA – now present in almost all populations from the European continent.

The research was conducted by an international team led by scientists from Cambridge University, Trinity College Dublin and University College Dublin. The findings are published today in the journal Nature Communications.       

“The question of where the Yamnaya come from has been something of a mystery up to now,” said one of the lead senior authors Dr Andrea Manica, from Cambridge’s Department of Zoology.

“We can now answer that as we’ve found that their genetic make-up is a mix of Eastern European hunter-gatherers and a population from this pocket of Caucasus hunter-gatherers who weathered much of the last Ice Age in apparent isolation. This Caucasus pocket is the fourth major strand of ancient European ancestry, one that we were unaware of until now,” he said   

Professor Daniel Bradley, leader of the Trinity team, said: “This is a major new piece in the human ancestry jigsaw, the influence of which is now present within almost all populations from the European continent and many beyond.”

Previously, ancient Eurasian genomes had revealed three ancestral populations that contributed to contemporary Europeans in varying degrees, says Manica.

Following the ‘out of Africa’ expansion, some hunter-gatherer populations migrated north-west, eventually colonising much of Europe from Spain to Hungary, while other populations settled around the eastern Mediterranean and Levant, where they would develop agriculture around 10,000 years ago. These early farmers then expanded into and colonised Europe.  

Lastly, at the start of the Bronze Age around 5,000 years ago, there was a wave of migration from central Eurasia into Western Europe – the Yamnaya.

However, the sequencing of ancient DNA recovered from two separate burials in Western Georgia – one over 13,000 years old, the other almost 10,000 years old – has enabled scientists to reveal that the Yamnaya owed half their ancestry to previously unknown and genetically distinct hunter-gatherer sources: the fourth strand.

By reading the DNA, the researchers were able to show that the lineage of this fourth Caucasus hunter-gatherer strand diverged from the western hunter-gatherers just after the expansion of anatomically modern humans into Europe from Africa.  

The Caucasus hunter-gatherer genome showed a continued mixture with the ancestors of the early farmers in the Levant area, which Manica says makes sense given the relative proximity. This ends, however, around 25,000 years ago – just before the time of the last glacial maximum, or peak Ice Age.

At this point, Caucasus hunter-gatherer populations shrink as the genes homogenise, a sign of breeding between those with increasingly similar DNA. This doesn’t change for thousands of years as these populations remain in apparent isolation in the shelter of the mountains – possibly cut off from other major ancestral populations for as long as 15,000 years – until migrations began again as the Glacial Maximum recedes, and the Yamnaya culture ultimately emerges. 

“We knew that the Yamnaya had this big genetic component that we couldn’t place, and we can now see it was this ancient lineage hiding in the Caucasus during the last Ice Age,” said Manica.

While the Caucasus hunter-gatherer ancestry would eventually be carried west by the Yamnaya, the researchers found it also had a significant influence further east. A similar population must have migrated into South Asia at some point, says Eppie Jones, a PhD student from Trinity College who is the first author of the paper.

“India is a complete mix of Asian and European genetic components. The Caucasus hunter-gatherer ancestry is the best match we’ve found for the European genetic component found right across modern Indian populations,” Jones said. Researchers say this strand of ancestry may have flowed into the region with the bringers of Indo-Aryan languages.   

The widespread nature of the Caucasus hunter-gatherer ancestry following its long isolation makes sense geographically, says Professor Ron Pinhasi, a lead senior author from University College Dublin. “The Caucasus region sits almost at a crossroads of the Eurasian landmass, with arguably the most sensible migration routes both west and east in the vicinity.”

He added: “The sequencing of genomes from this key region will have a major impact on the fields of palaeogeneomics and human evolution in Eurasia, as it bridges a major geographic gap in our knowledge.”

David Lordkipanidze, Director of the Georgian National Museum and co-author of the paper, said: “This is the first sequence from Georgia – I am sure soon we will get more palaeogenetic information from our rich collections of fossils.”

Inset image: the view from the Satsurblia cave in Western Georgia, where a human right temporal bone dating from over 13,000 years ago was discovered. DNA extracted from this bone was used in the new research.

E.R. Jones et. al. ‘Upper Palaeolithic genomes reveal deep roots of modern Eurasians.’ Nature Communications (2015). DOI: 10.1038/ncomms9912

Populations of hunter-gatherers weathered Ice Age in apparent isolation in Caucasus mountain region for millennia, later mixing with other ancestral populations, from which emerged the Yamnaya culture that would bring this Caucasus hunter-gatherer lineage to Western Europe.

This Caucasus pocket is the fourth major strand of ancient European ancestry, one that we were unaware of until now
Andrea Manica
DNA was extracted from the molar teeth of this skeleton, dating from almost 10,000 years ago and found in the Kotias Klde rockshelter in Western Georgia.

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Pevensey giant whale remembered 150 years on

From Department of Zoology. Published on Nov 16, 2015.

Opinion: Why cats are fussy eaters but dogs will consume almost anything

By Anonymous from University of Cambridge - Department of Zoology. Published on Nov 13, 2015.

Anyone who’s watched a cat throwing up after munching on grass knows that our feline friends aren’t natural plant eaters. So you might be surprised to discover that these carnivorous animals share some important genes that are more typically associated with herbivores. And this might help explain why cats aren’t always easy to please when it comes to food.

New research suggests that cats possess the genes that protect vegetarian animals from ingesting poisonous plants by giving them the ability to taste bitter. Animals use their sense of taste to detect whether a potential food is nutritious or harmful. A sweet taste signals the presence of sugars, an important source of energy. A bitter taste, on the other hand, evolved as a defence mechanism against harmful toxins commonly found in plants and unripe fruits.

Evolution has repeatedly tweaked animals' taste buds to suit various dietary needs. Changes in an animal’s diet can eliminate the need to sense certain chemicals in food, and so receptor genes mutate, destroying their ability to make a working protein.


I can haz chlorophyll. Lisa Sympson/Wikimedia Commons, CC BY-SA


One example of this comes from strictly meat-eating cats, who can no longer taste sweetness. But if bitter detection evolved to warn of plant toxins, then it stands to reason that cats, which (usually) eschew plants, shouldn’t be able to taste bitter either. Humans and other vegetable-munching animals can taste bitter because we possess bitter taste receptor genes. If cats have lost the ability to taste bitterness, we should find that their receptor genes are riddled with mutations.

Geneticists at the Monell Chemical Senses Center in Philadelphia scoured the genome of cats and other carnivorous mammals like dogs, ferrets, and polar bears to see if our carnivorous cousins have bitter genes. They were surprised to find that cats have 12 different genes for bitter taste. Dogs, ferrets, and polar bears are equally well endowed. So, if meat eating animals are unlikely to encounter any bitter morsels, why do they boast genes for tasting bitterness?

Taste test

To find out, Peihua Jiang, a molecular biologist at Monell, put cat taste buds to the test. He inserted the cat taste receptor gene into human tissue cells in the lab. When combined, the cell and the gene act as a taste receptor that responds to chemicals dropped onto it.

Jiang discovered that the cat’s taste receptors responded to bitter chemicals found in toxic plants and to compounds that also activate human bitter receptors. The cat bitter taste receptor, known as Tas2r2, responded to the chemical denatonium benzoate, a bitter substance commonly smeared on the fingernails of nail-biting children.

So why have cats retained the ability to detect bitter tastes? Domestic cats owners know how unpredictable cats' dietary choices can be. Some of the “presents” cats bring to their owners include frogs, toads, and other animals that can contain bitter and toxic compounds in their skin and bodies. Jiang’s results show that bitter receptors empower cats to detect these potential toxins, giving them the ability to reject noxious foods and avoid poisoning.


Hair of the dog. Michal Hrabovec/Flickr, CC BY-NC-SA


But how often do meat-loving cats actually get exposed to bitter and toxic compounds in their diet, compared with the plethora of plant toxins that their vegetarian counterparts have to contend with? Jiang suggests this is not enough to explain why cats have retained such an arsenal of receptors.

Instead, cat taste receptors may have evolved for reasons other than taste. In humans, bitter taste receptors are found not only in the mouth, but also in the heart and in the lungs, where they are thought to detect infections. It remains to be seen if feline bitter receptor genes also double-up as disease detectors.

The discovery of feline bitter receptors might explain why cats have got a reputation as picky eaters. But their unfussy canine counterparts have a similar number of bitter taste receptors – so why are cats so finicky? One answer might lie in how the cat receptors detect bitter-tasting compounds. Research published earlier this year by another team of researchers showed that some of the cat taste receptors are especially sensitive to bitter compounds, and even more sensitive to denatonium than the same receptor in humans.

Perhaps cats are also more sensitive to bitter chemicals than dogs, or they may detect a greater number of bitter compounds in their everyday diet. Food that tastes bland to us or to a dog could be an unpleasant gastronomic experience for cats. So rather than branding cats as picky, perhaps we should think of them as discerning feline foodies.

Hannah Rowland, Lecturer in Ecology and Evolution & Research Fellow at Zoological Society of London, University of Cambridge

This article was originally published on The Conversation. Read the original article.

The opinions expressed in this article are those of the individual author(s) and do not represent the views of the University of Cambridge.

Hannah Rowland (Department of Zoology) discusses why different animals have different tastes when it comes to food.

Hank The Cat Eating Tuna Fish

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Power up: cockroaches employ a “force boost” to chew through tough materials

By jeh98 from University of Cambridge - Department of Zoology. Published on Nov 11, 2015.

The study, published today in PLOS ONE, shows that cockroaches activate slow twitch muscle fibres only when chewing on tough material such as wood that requires repetitive, hard biting to generate a bite force 50 times stronger than their own body weight.

“As insects play a dominant role in many ecosystems, understanding the amount of force that these insects can exert through their mandibles is a pivotal step in better understanding behavioural and ecological processes and enabling bioinspired engineering,” explains Tom Weihmann from the University of Cambridge’s Department of Zoology, lead author of the study. “Insects provide a major part of the faunal biomass in many terrestrial ecosystems. Therefore they are an important food source but also crucial as decomposers of plants and animals. In this way they are crucial for material cycles and the ecological balance.”

 “Ours is the first study to measure the bite forces of ordinary insects, and we found that the American cockroach, Periplaneta americana, can generate a bite force around 50 times stronger than their own body weight. In relative terms that’s about five times stronger than the force a human can generate with their jaws,” he adds.

Previous studies have focused on the biting action of larger animals, particularly vertebrates, which have jaws full of teeth that they use to grind food, catch prey, or fend off other animals. But insects, like cockroaches, have different biting mouthparts; they have a pair of strong, horizontally aligned bladelike jaws, or mandibles. The mandibles have an important role in the life of insects: being used not only for shredding food, but also for digging, transport, defence, and feeding offspring.

An insect’s mandibles are attached to the head capsule, which consists of thin multi-layered cuticle and forms a complexly structured part of their exoskeleton. The head capsule encloses the driving muscles for all mouth parts and a number of other vital organs of the central nervous and digestive systems. This means that space is limited for the muscles required to operate their scissor-like mandibles; so many insects have muscles with oblique fibres that reduce the amount of thickening that occurs when the muscles contract.

When it comes to investigating biting, cockroaches are the perfect model system – as Weihmann says, they are “extraordinarily ordinary insects with regard to their mouthparts and biting abilities.”

The researchers measured the force of 300 bites made by specimen cockroaches across the whole range of mandible opening angles. They found that the cockroaches could exert various levels of force with their bites, from short, weak bites, to particularly strong bites that lasted much longer.

“The weaker, shorter bites were generated by relatively fast muscle fibres, while the longer, stronger bites were driven by additional muscle fibres that take time to reach their maximum force,” explains Weihmann, “these slower muscle fibres give the mandibles a force boost to allow them to exert up to 0.5 Newtons during sustained grasping or chewing.”

“The employment of slow muscle fibres allows very efficiently generated muscle forces with only a minimum of cross section area, and therefore head volume, required,” he adds.

Weihmann explains that gaining a better understanding of how the delicate structure of the head capsule withstands such powerful forces over an insect’s lifetime could also have interesting applications for bioinspired engineering.

“It is interesting whenever forces have to be transferred within small hollow capsules, particularly if actuators such as tiny motors, advanced piezo-electric actuators or other sophisticated drives need to be attached to the inner sides of the structure, just like mandible muscles do. With increasing miniaturisation, such designs will become increasingly important. Recent technical implementations in this direction are for instance micro probes inserted into blood vessels or micro surgical instruments.”

The work was funded by the German Research Foundation (DFG) and the Daimler and Benz Foundation.


Tom Weihmann, et al. Fast and powerful: Biomechanics and bite forces of the mandibles in the American cockroach Periplaneta Americana PLOS ONE 11th November 2015.

Inset images: A side view onto the experimental setup with the force sensor at the left and the specimen at the right (Tom Weihmann); A micro-computed tomography image of a cockroach head showing the driving muscles of the left mandible (Tom Weihmann).

New research indicates that cockroaches use a combination of fast and slow twitch muscle fibres to give their mandibles a “force boost” that allows them to chew through tough materials.

The American cockroach can generate a bite force around 50 times stronger than their own body weight – in relative terms about five times stronger than the force a human can generate with their jaws
Tom Weihmann
Left - micro-computed tomography image of a cockroach head showing the driving muscles of the left mandible; right - side view onto the experimental setup

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X is for Xenarthran

By amb206 from University of Cambridge - Department of Zoology. Published on Nov 11, 2015.

Xenarthra is an order of primarily South American mammals that includes sloths, ant-eaters and armadillos. Several are sufficiently endangered to be on the IUCN ‘red list’. In previous millenia, the group was far bigger. It covered many other creatures, now extinct, such as giant ground sloths estimated to have exceeded the size of a male African elephant.

As ‘exotic’ animals, xenarthrans have long fascinated westerners and became a must-have item in ‘cabinets of curiosities’ – collections gathered from a world that was opening up to exploration from the 15th century onwards. In the mid-17th century, the naturalist-physician, Georg Marcgrave, stationed in Dutch Brazil, described the armadillos that he encountered:

"The Tatu or Tatu-peba in Brazilian, Armadillo in Spanish, Encuberto in Portuguese, we Belgians call Armoured-piglet. It is a most powerful animal that lives in the ground, though also in water and soggy places. It is found in various sizes."

As a consequence of the blossoming of scientific enquiry in the 19th century, many leading zoology museums have examples of xenarthrans in their collections. Cambridge’s Museum of Zoology, for example, has a fine collection of specimens collected on expeditions to South America, from the diminutive Pink Fairy Armadillo (Chlamyphorus truncatus) to the towering giant ground sloth (Megatherium americanum) which became extinct some 10,000 years ago.

The ground sloth is one of a number of relatively recently extinct large sloths, one of which Charles Darwin himself helped discover on the voyage of the Beagle. On September 18, 1832, Darwin noted in his dairy that he had dined on “Ostrich dumpling & Armadillos”. The ‘ostrich’ he ate was, in fact, rhea; the abundant armadillos were a staple diet of the local gauchos.

Not long afterwards, Darwin saw for the first time fossils of shells and other animals, embedded in soft sea cliffs, including a specimen of giant ground sloth which was to be named Mylodon darwinii  in his honour.

Xenarthans have been a source of fascination to Dr Robert Asher, an evolutionary biologist in the Department of Zoology, ever since he first began studying mammalian diversity as a graduate student some 20 years ago. He’s particularly interested in the evolutionary stories told by the structure of their skeletons – and the ways in which their bones act as clues to their relative position within the tree of life.

Natural history museums in Berlin, Paris and London have in their collections examples of three-toed sloths, including embryos and foetuses. These specimens enabled Dr Robert Asher and his colleague Dr Lionel Hautier (formerly a Cambridge postdoctoral fellow and now at the University of Montpellier) to publish research on an aspect of the anatomy of sloths which sets them apart from almost every other mammal on earth.

The difference lies in the arrangement of vertebrae in sloths’ spinal columns – which can be seen as clues to xenarthrans’ divergent evolutionary pathways over the past few million years.

You might think that animals with long necks would have more neck vertebrae than those with short necks. This is certainly true of some birds and reptiles. But almost every placental mammal on earth (some 5,000 species in total) has seven ‘ribless’ vertebrae in the neck – even creatures with long necks such as giraffes. The three-toed sloth deviates from this rule: many of these tree-living creatures have eight, nine or even ten cervical vertebrae. 

This remarkable diversity was noticed in the 18th century and scientists continue to tease apart the mechanisms by which mammals deviate from the “rule of seven”. In 2009, Asher and colleagues set out to learn more about this intriguing quirk. Neck vertebrae are known as cervicals and the rib-bearing vertebrae below them are known as thoracics. Thoracic vertebrae have facets which allow articulation with the ribs.

Asher and colleagues looked at patterns of bone formation in mammals as they developed. They found that, in all mammals, the centrum (or middle part) of the first thoracic (number eight, counting down from the skull) turns from cartilage to bone earlier than the centra of the posterior-most cervicals. In sloths, too, the eighth vertebrae begins to develop early – but, in their case, this ribless vertebra is located in the neck and generally considered to be ‘cervical’.

“The ‘extra’ vertebrae in sloths’ necks have the same developmental  characteristics as thoracic vertebrae. They are, in effect, ribcage vertebrae, masquerading as neck vertebrae. In sloths, the position of the shoulders, pelvis and ribcage are linked with one another, and compared to their common ancestor shared with other mammals, have shifted down the vertebral column to make the neck longer,” explains Asher.

“Even in sloths, the mammalian ‘rule of seven’ applies to the vertebral centra. The ossification of the centra in a long-necked sloth resembles ossification in other mammals. However, sloths can deviate from the “rule” by shifting the embryonic tissues that give rise to the limb girdles and rib cage relative to the vertebrae, adding what are essentially one or more ribcage vertebrae into the caudal end of their neck. The next question to address is why and how sloths managed this shift.”

Xenarthrans also pack some intriguing surprises when it comes to teeth. Anteaters have no teeth. Sloths have just one set of teeth to see them through life – as do all but one genus of armadillo. Armadillos in the genus Dasypus (including seven- and nine-banded species) are unlike other armadillos in having two sets of teeth during their lifespan: deciduous (or ‘milk’) teeth and permanent teeth.

Most mammals, including humans, shed their baby teeth while they are growing. Recent research by Asher and colleagues from the University of La Plata, Argentina, into the dentition of Dasypus revealed that its permanent teeth erupt long after the animal reaches its full size. “The equivalent scenario in a human would be losing your milk teeth, and gaining all your permanent ones, once you were fully grown and well into your 20s,” says Asher.

In this regard, Dasypus is similar to most species of endemic African mammals (Afrotheria) – a group of animals that includes elephants, manatees, tenrecs, golden moles and sengis. “Eruption of adult teeth after the attainment of full body size and sexual maturity is not unheard of in other mammals,” says Asher. “Some people reading this won’t yet have erupted their ‘wisdom’ teeth or third molars. But few groups do this as pervasively as Afrotherians and Dasypus.“

With gratitude to PhD candidate Natalie Lawrence (Department of History and Philosophy of Science) for her input on early western encounters with ‘exotic’ animals.

Next in the Cambridge Animal Alphabet: Y is for an animal that is an integral part of high-altitude livelihoods throughout the Himalayas, Tibet and Central Asia.

Have you missed the series so far? Catch up on Medium here.

Inset images: Illustration of an armadillo from Historiae Naturalis Brasilae Tatu by Georg Marcgrave; Skeleton of a giant land sloth (Museum of Zoology); Three-toed sloth - Bradypodidae - Luiaard (Martha de Jong-Lantink); Lateral view of 3D reconstruction of computerized tomography (CT) scans of skeleton in the three-toed sloth Bradypus (Hautier et al).

The Cambridge Animal Alphabet series celebrates Cambridge’s connections with animals through literature, art, science and society. Here, X is for Xenarthran. A must-have item for 15th-century collectors of 'curiosities' and a source of fascination for evolutionary biologist Dr Robert Asher.

It is a most powerful animal that lives in the ground, though also in water and soggy places
Georg Marcgrave

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Plague in humans ‘twice as old’ but didn’t begin as flea-borne, ancient DNA reveals

By fpjl2 from University of Cambridge - Department of Zoology. Published on Oct 22, 2015.

New research using ancient DNA has revealed that plague has been endemic in human populations for more than twice as long as previously thought, and that the ancestral plague would have been predominantly spread by human-to-human contact – until genetic mutations allowed Yersinia pestis (Y. pestis), the bacterium that causes plague, to survive in the gut of fleas.

These mutations, which may have occurred near the turn of the 1st millennium BC, gave rise to the bubonic form of plague that spreads at terrifying speed through flea – and consequently rat – carriers. The bubonic plague caused the pandemics that decimated global populations, including the Black Death, which wiped out half the population of Europe in the 14th century.  

Before its flea-borne evolution, however, researchers say that plague was in fact endemic in the human populations of Eurasia at least 3,000 years before the first plague pandemic in historical records (the Plague of Justinian in 541 AD).

They say the new evidence that Y. pestis bacterial infection in humans actually emerged around the beginning of the Bronze Age suggests that plague may have been responsible for major population declines believed to have occurred in the late 4th and early 3rd millennium BC.   

The work was conducted by an international team including researchers from the universities of Copenhagen, Denmark, and Cambridge, UK, and the findings are published today in the journal Cell

“We found that the Y. pestis lineage originated and was widespread much earlier than previously thought, and we narrowed the time window as to when and how it developed,” said senior author Professor Eske Willerslev, who recently joined Cambridge University’s Department of Zoology from the University of Copenhagen. 

“The underlying mechanisms that facilitated the evolution of Y. pestis are present even today. Learning from the past may help us understand how future pathogens may arise and evolve,” he said.

Researchers analysed ancient genomes extracted from the teeth of 101 adults dating from the Bronze Age and found across the Eurasian landmass.

They found Y. pestis bacteria in the DNA of seven of the adults, the oldest of whom died 5,783 years ago – the earliest evidence of plague. Previously, direct molecular evidence for Y. pestis had not been obtained from skeletal material older than 1,500 years.  

However, six of the seven plague samples were missing two key genetic components found in most modern strains of plague: a “virulence gene” called ymt, and a mutation in an “activator gene” called pla.

The ymt gene protects the bacteria from being destroyed by the toxins in flea guts, so that it multiplies, choking the flea’s digestive tract. This causes the starving flea to frantically bite anything it can, and, in doing so, spread the plague.

The mutation in the pla gene allows Y. pestis bacteria to spread across different tissues, turning the localised lung infection of pneumonic plague into one of the blood and lymph nodes.

Researchers concluded these early strains of plague could not have been carried by fleas without ymt. Nor could they cause bubonic plague – which affects the lymphatic immune system, and inflicts the infamous swollen buboes of the Black Death – without the pla mutation.

Consequently, the plague that stalked populations for much of the Bronze Age must have been pneumonic, which directly affects the respiratory system and causes desperate, hacking coughing fits just before death. Breathing around infected people leads to inhalation of the bacteria, the crux of its human-to-human transmission.   

Study co-author Dr Marta Mirazón-Lahr, from Cambridge’s Leverhulme Centre for Human Evolutionary Studies (LCHES), points out that a study earlier this year from Willerslev’s Copenhagen group showed the Bronze Age to be a highly active migratory period, which could have led to the spread of pneumonic plague.

“The Bronze Age was a period of major metal weapon production, and it is thought increased warfare, which is compatible with emerging evidence of large population movements at the time. If pneumonic plague was carried as part of these migrations, it would have had devastating effects on small groups they encountered,” she said.   

“Well-documented cases have shown the pneumonic plague’s chain of infection can go from a single hunter or herder to ravaging an entire community in two to three days.”

The most recent of the seven ancient genomes to reveal Y. pestis in the new study has both of the key genetic mutations, indicating an approximate timeline for the evolution that spawned flea-borne bubonic plague.

“Among our samples, the mutated plague strain is first observed in Armenia in 951 BC, yet is absent in the next most recent sample from 1686 BC – suggesting bubonic strains evolve and become fixed in the late 2nd and very early 1st millennium BC,” said Mirazón-Lahr.

“However, the 1686 BC sample is from the Altai mountains near Mongolia. Given the distance between Armenia and Altai, it’s also possible that the Armenian strain of bubonic plague has a longer history in the Middle East, and that historical movements during the 1st millennium BC exported it elsewhere.”

The Books of Samuel in the Bible describe an outbreak of plague among the Philistines in 1320 BC, complete with swellings in the groin, which the World Health Organization has argued fits the description of bubonic plague. Mirazón-Lahr suggests this may support the idea of a Middle Eastern origin for the plague’s highly lethal genetic evolution.

Co-author Professor Robert Foley, also from Cambridge’s LCHES, suggests that the lethality of bubonic plague may have required the right population demography before it could thrive. 

“Every pathogen has a balance to maintain. If it kills a host before it can spread, it too reaches a ‘dead end’. Highly lethal diseases require certain demographic intensity to sustain them.

“The endemic nature of pneumonic plague was perhaps more adapted for an earlier Bronze Age population. Then, as Eurasian societies grew in complexity and trading routes continued to open up, maybe the conditions started to favour the more lethal form of plague,” Foley said.  

“The Bronze Age is the edge of history, and ancient DNA is making what happened at this critical time more visible,” he said.

Willerslev added: “These results show that the ancient DNA has the potential not only to map our history and prehistory, but also discover how disease may have shaped it.”

Inset image: Map showing where the remains of the Bronze Age plague victims were found.

New research dates plague back to the early Bronze Age, showing it had been endemic in humans across Eurasia for millennia prior to first recorded global outbreak, and that ancestral plague mutated into its bubonic, flea-borne form between the 2nd and 1st millennium BC.

These results show that the ancient DNA has the potential not only to map our history and prehistory, but also discover how disease may have shaped it
Eske Willerslev
Left: Skull of a Yamnaya, the people who migrated to Central Asia in early Bronze Age and developed the Afanasievo culture. The Afanasievo are one of the Bronze Age groups carrying Y. pestis. Right: Scanning Electron Micrograph Of A Flea

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Using experts ‘inexpertly’ leads to policy failure, warn researchers

By fpjl2 from University of Cambridge - Department of Zoology. Published on Oct 14, 2015.

The accuracy and reliability of expert advice is often compromised by “cognitive frailties”, and needs to be interrogated with the same tenacity as research data to avoid weak and ill-informed policy, warn two leading risk analysis and conservation researchers in the journal Nature today

While many governments aspire to evidence-based policy, the researchers say the evidence on experts themselves actually shows that they are highly susceptible to “subjective influences” – from individual values and mood, to whether they stand to gain or lose from a decision – and, while highly credible, experts often vastly overestimate their objectivity and the reliability of peers.   

The researchers caution that conventional approaches of informing policy by seeking advice from either well-regarded individuals or assembling expert panels needs to be balanced with methods that alleviate the effects of psychological and motivational bias.

They offer a straightforward framework for improving expert advice, and say that experts should provide and assess evidence on which decisions are made – but not advise decision makers directly, which can skew impartiality.

“We are not advocating replacing evidence with expert judgements, rather we suggest integrating and improving them,” write professors William Sutherland and Mark Burgman from the universities of Cambridge and Melbourne respectively.

“Policy makers use expert evidence as though it were data. So they should treat expert estimates with the same critical rigour that must be applied to data,” they write.

“Experts must be tested, their biases minimised, their accuracy improved, and their estimates validated with independent evidence. Put simply, experts should be held accountable for their opinions.”

Sutherland and Burgman point out that highly regarded experts are routinely shown to be no better than novices at making judgements.

However, several processes have been shown to improve performances across the spectrum, they say, such as ‘horizon scanning’ – identifying all possible changes and threats – and ‘solution scanning’ – listing all possible options, using both experts and evidence, to reduce the risk of overlooking valuable alternatives.

To get better answers from experts, they need better, more structured questions, say the authors. “A seemingly straightforward question, ‘How many diseased animals are there in the area?’ for example, could be interpreted very differently by different people. Does it include those that are infectious and those that have recovered? What about those yet to be identified?” said Sutherland, from Cambridge’s Department of Zoology.

“Structured question formats that extract upper and lower boundaries, degrees of confidence and force consideration of alternative theories are important for shoring against slides into group-think, or individuals getting ascribed greater credibility based on appearance or background,” he said.

When seeking expert advice, all parties must be clear about what they expect of each other, says Burgman, Director of the Centre of Excellence for Biosecurity Risk Analysis. “Are policy makers expecting estimates of facts, predictions of the outcome of events, or advice on the best course of action?”

“Properly managed, experts can help with estimates and predictions, but providing advice assumes the expert shares the same values and objectives as the decision makers. Experts need to stick to helping provide and assess evidence on which such decisions are made,” he said. 

Sutherland and Burgman have created a framework of eight key ways to improve the advice of experts. These include using groups – not individuals – with diverse, carefully selected members well within their expertise areas.

They also caution against being bullied or “starstruck” by the over-assertive or heavyweight. “People who are less self-assured will seek information from a more diverse range of sources, and age, number of qualifications and years of experience do not explain an expert’s ability to predict future events – a finding that applies in studies from geopolitics to ecology,” said Sutherland.

Added Burgman: “Some experts are much better than others at estimation and prediction. However, the only way to tell a good expert from a poor one is to test them. Qualifications and experience don’t help to tell them apart.”

“The cost of ignoring these techniques – of using experts inexpertly – is less accurate information and so more frequent, and more serious, policy failures,” write the researchers. 

Evidence shows that experts are frequently fallible, say leading risk researchers, and policy makers should not act on expert advice without using rigorous methods that balance subjective distortions inherent in expert estimates.

The cost of ignoring these techniques – of using experts inexpertly – is less accurate information and so more frequent, and more serious, policy failures
William Sutherland and Mark Burgman
Experts Only

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Ancient genome from Africa sequenced for the first time

By fpjl2 from University of Cambridge - Department of Zoology. Published on Oct 08, 2015.

The first ancient human genome from Africa to be sequenced has revealed that a wave of migration back into Africa from Western Eurasia around 3,000 years ago was up to twice as significant as previously thought, and affected the genetic make-up of populations across the entire African continent.

The genome was taken from the skull of a man buried face-down 4,500 years ago in a cave called Mota in the highlands of Ethiopia – a cave cool and dry enough to preserve his DNA for thousands of years. Previously, ancient genome analysis has been limited to samples from northern and arctic regions.

The latest study is the first time an ancient human genome has been recovered and sequenced from Africa, the source of all human genetic diversity. The findings are published today in the journal Science.

The ancient genome predates a mysterious migratory event which occurred roughly 3,000 years ago, known as the ‘Eurasian backflow’, when people from regions of Western Eurasia such as the Near East and Anatolia suddenly flooded back into the Horn of Africa.

The genome enabled researchers to run a millennia-spanning genetic comparison and determine that these Western Eurasians were closely related to the Early Neolithic farmers who had brought agriculture to Europe 4,000 years earlier.

By comparing the ancient genome to DNA from modern Africans, the team have been able to show that not only do East African populations today have as much as 25% Eurasian ancestry from this event, but that African populations in all corners of the continent – from the far West to the South – have at least 5% of their genome traceable to the Eurasian migration.      

Researchers describe the findings as evidence that the ‘backflow’ event was of far greater size and influence than previously thought. The massive wave of migration was perhaps equivalent to over a quarter of the then population of the Horn of Africa, which hit the area and then dispersed genetically across the whole continent.

“Roughly speaking, the wave of West Eurasian migration back into the Horn of Africa could have been as much as 30% of the population that already lived there – and that, to me, is mind-blowing. The question is: what got them moving all of a sudden?” said Dr Andrea Manica, senior author of the study from the University of Cambridge’s Department of Zoology.    

Previous work on ancient genetics in Africa had involved trying to work back through the genomes of current populations, attempting to eliminate modern influences. “With an ancient genome, we have a direct window into the distant past. One genome from one individual can provide a picture of an entire population,” said Manica.  

The cause of the West Eurasian migration back into Africa is currently a mystery, with no obvious climatic reasons. Archaeological evidence does, however, show the migration coincided with the arrival of Near Eastern crops into East Africa such as wheat and barley, suggesting the migrants helped develop new forms of agriculture in the region.      

The researchers say it’s clear that the Eurasian migrants were direct descendants of, or a very close population to, the Neolithic farmers that had had brought agriculture from the Near East into West Eurasia around 7,000 years ago, and then migrated into the Horn of Africa some 4,000 years later. “It’s quite remarkable that genetically-speaking this is the same population that left the Near East several millennia previously,” said Eppie Jones, a geneticist at Trinity College Dublin who led the laboratory work to sequence the genome. 

While the genetic make-up of the Near East has changed completely over the last few thousand years, the closest modern equivalents to these Neolithic migrants are Sardinians, probably because Sardinia is an isolated island, says Jones. “The famers found their way to Sardinia and created a bit of a time capsule. Sardinian ancestry is closest to the ancient Near East.” 

View looking out from the Mota cave in the Ethiopian highlands

“Genomes from this migration seeped right across the continent, way beyond East Africa, from the Yoruba on the western coast to the Mbuti in the heart of the Congo – who show as much as 7% and 6% of their genomes respectively to be West Eurasian,” said Marcos Gallego Llorente, first author of the study, also from Cambridge’s Zoology Department.

“Africa is a total melting pot. We know that the last 3,000 years saw a complete scrambling of population genetics in Africa. So being able to get a snapshot from before these migration events occurred is a big step,” Gallego Llorente said.

The ancient Mota genome allows researchers to jump to before another major African migration: the Bantu expansion, when speakers of an early Bantu language flowed out of West Africa and into central and southern areas around 3,000 years ago. Manica says the Bantu expansion may well have helped carry the Eurasian genomes to the continent’s furthest corners.

The researchers also identified genetic adaptations for living at altitude, and a lack of genes for lactose tolerance – all genetic traits shared by the current populations of the Ethiopian highlands. In fact, the researchers found that modern inhabitants of the area highlands are direct descendants of the Mota man.

Finding high-quality ancient DNA involves a lot of luck, says Dr Ron Pinhasi, co-senior author from University College Dublin. “It’s hard to get your hands on remains that have been suitably preserved. The denser the bone, the more likely you are to find DNA that’s been protected from degradation, so teeth are often used, but we found an even better bone – the petrous.” The petrous bone is a thick part of the temporal bone at the base of the skull, just behind the ear.  

“The sequencing of ancient genomes is still so new, and it’s changing the way we reconstruct human origins,” added Manica. “These new techniques will keep evolving, enabling us to gain an ever-clearer understanding of who our earliest ancestors were.” 

The study was conducted by an international team of researchers, with permission from the Ethiopia’s Ministry of Culture and Authority for Research and Conservation of Cultural Heritage.

DNA from 4,500-year-old Ethiopian skull reveals a huge migratory wave of West Eurasians into the Horn of Africa around 3,000 years ago had a genetic impact on modern populations right across the African continent.

The sequencing of ancient genomes is still so new, and it’s changing the way we reconstruct human origins
Andrea Manica
Archaeologists outside the entrance to the Mota cave in the Ethiopian highlands, where the remains containing the ancient genome were discovered.

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How the stick insect sticks (and unsticks) itself

By jeh98 from University of Cambridge - Department of Zoology. Published on Oct 07, 2015.

Geckos, tree frogs, spiders and insects all share a special skill – they can walk up vertical surfaces and even upside down using adhesive pads on their feet. But geckos have ‘dry’ feet, while insects have ‘wet’ feet.

Scientists have assumed that the two groups use different mechanisms to keep their feet firmly attached to a surface, but new research from David Labonte and Dr Walter Federle in the University of Cambridge’s Department of Zoology provides evidence that this isn’t actually the case.

“It has generally been assumed that the fluid on their feet must be involved in helping insects like stick insects adhere to a surface by capillary and viscous forces – in the same way that a beer glass will stick to a glass table if it’s wet on the bottom,” explains Labonte, lead author of the study published in Soft Matter, “but our research shows that the fluid is likely used for something else entirely – it may even help insects unstick their feet.”

By measuring how much force was required to detach the foot of a stick insect from a glass plate at different speeds and applying the theory of fracture mechanics, Labonte and Federle found that only a ‘dry’ contact model could explain the data. They also carried out a comparison of the sticking performance of wet and dry adhesive pads, which revealed that there is a striking lack of differences between the two, contrary to previous opinion.

Insects and geckos need to walk up vertical surfaces and even upside down in order to get to the places where they feed and to escape from predators. As smooth surfaces don’t allow them to grip with their claws, they need soft adhesive pads on their feet and legs. This means they need to have excellent control over adhesion – to ensure their feet stick when they want them to, but can also unstick easily to allow them to walk around or run away from predators.

“Both wet and dry adhesive pads behave in a similar way to soft, rubbery materials in that, when they are pressed against another surface, there is a large area of contact between the two surfaces,” says Labonte. Both pad types then rely on shear forces to control their stickiness: insect and gecko feet are much stickier when they are pulled towards the body.

“The fluid that insects have on their adhesive pads doesn’t seem to increase the pads' stickiness by means of capillary or viscous forces, and the same may hold for the fluid on the feet of spiders and tree frogs.”

So what is this fluid for?

Labonte and Federle believe it may act as a ‘release layer’ to help insects unstick their feet when they want to move. “If you think of commercial adhesives, like Scotch tape, there are often bits of tape or residue left behind when you remove it quickly. But a stick insect needs to be able to unstick its feet without expending a lot of energy or leaving bits of its foot still stuck to a leaf,” explains Federle.

“The fluid may act as a lubricant to make detachment easier, giving insects greater control over adhesion at very short timescales.”

“When the first microscopes were invented in the 17th century, one of the first things scientists looked at was a fly’s foot. The purpose of the fluid that you find on insects’ feet has remained a fascinating question ever since,” says Labonte.

But it’s not just an age-old question that this research is helping to answer. The researchers say there may be lessons to learn for modern manmade devices.

“Understanding how insects control adhesion could have applications where adhesion is needed in a dynamic context, for instance in the production of small electronic devices, where it’s necessary to pick up and place down tiny parts with ease and accuracy,” adds Federle.

This research was enabled by funding from the Biotechnology and Biological Sciences Research Council and the Human Frontier Science Programme.


David Labonte and Walter Federle ‘Rate-dependence of ‘wet’ biological adhesives and the function of the pad secretion in insectsSoft Matter (2015).

Inset images: Composite figure showing the adhesive pad on the foot of a stick insect (T Endlein and David Labonte); Stick insect (T Endlein); Ant's foot showing a fluid trail (Walter Federle).

New research shows the fluid found on insects’ feet does not help them adhere to vertical and inverted surfaces, as previously thought, but may in fact help them to unstick their feet more easily to allow greater control over their sticking power.

When the first microscopes were invented in the 17th century, one of the first things scientists looked at was a fly’s foot. The purpose of the fluid that you find on insects’ feet has remained a fascinating question ever since
David Labonte
Ant's foot showing a fluid trail

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Q is for Queen Bumblebee

By amb206 from University of Cambridge - Department of Zoology. Published on Sep 23, 2015.

Each autumn, colonies of bumblebees die. All, that is, apart from the gravid (egg-carrying) queens who survive the winter in tiny burrows in the ground.  Early in the spring, the queen emerges to start making a nest in which to lay her eggs. To do so, she needs the energy provided by nectar and pollen. If she can’t find enough flowers from which to gather these resources, she will die – and the next generation she is carrying will die too.

Bumblebees are among the UK’s estimated 1,500 species of wild pollinators and play a vital role in the environment. They transfer pollen from plant to plant – and thus ensure that plants reproduce. An estimated 75% of the crops we eat depend on pollination. Bumblebees are particularly important pollinators of beans, raspberries and tomatoes. Uniquely, they are capable of ‘buzz pollination’, producing a high-pitched buzz which releases pollen from pollen-containing tubes inside some flowers. Tomatoes are pollinated like this.

Over the past 80 years or so, there has been a dramatic decline in the distributions of some bumblebee species. Two of the 26 species of bumblebee once common in the UK are now extinct. Scientists think that the factors behind this decline are several and interconnected. Most obvious is the loss of wild flower meadows which have disappeared as farming has become more intensive and fields made larger by the removal of hedgerows. Although many British gardens burst with flowers, many of the showy favourites (such as pansies and begonias) produce little pollen or nectar.

A recent report by Dr Lynn Dicks (Department of Zoology) and staff at Natural England makes an important contribution to the development of nation-wide strategies to halt – and reverse – the loss of wild pollinators such as bumblebees. In 2013, a rare and time-limited opportunity opened up for scientists to contribute to the development of an ‘agri-environment package’ for wild pollinators as part of the new Countryside Stewardship scheme, launched earlier this year.

As an expert in the ecology of flower-visiting insects, Dicks used this ‘policy window’ to bring together a wide range of available information and ask key questions about wild pollinators and their relationship with the farmed environment. In providing tentative answers to these questions, her paper provides ballpark figures on aspects of land management that determine population levels of wild pollinators, including bumblebees, and bolsters arguments for policies that encourage farmers to sow a mix of wild flowers.

“An agri-environment package is a bundle of management options that supply sufficient resources to support a target group of species. Data from a similar package, aimed at helping farmers provide resources for species of birds known to be declining, are not yet publically available. But some of the measures in the package are known to have led to an upturn in numbers of six target species – including skylarks and yellowhammers – which is most encouraging,” says Dicks.

“We depend on pollinators for food production so it’s in our interests to halt drops in numbers. If species are declining, it’s because they lack specific resources – or because other factors are reducing their numbers faster than they can reproduce. Some risks to pollinators – notably pesticides and climate change – are difficult to quantify and politically challenging. An alternative is to focus policy on providing the resources that are lacking – such as nectar-rich flowers.”

The most critical period for bumblebee survival is March and April when the queens that have hibernated over the winter need access to enough nectar and pollen to raise their first batch of workers within an estimated 1km radius of their nests. The first batch of eggs laid by the queen become female workers whose role is to feed the new colony by visiting flowers to gather nectar.  Throughout the summer the queen will produce further batches of eggs, seldom leaving the nest. She will eventually control a nest of as many as 400 individuals, including new queens. Honeybee hives, in comparison, typically contain around 50,000 bees.

Many commercial crops flower several weeks after the queen bumblebees are most in need of nectar. Oil seed rape, for example, produces its bright yellow flowers in May and June. Nectar and pollen provided by these crops are valuable to later batches of bumblebees. However, the first batch of bumblebees relies on plants that flower in early spring – including those associated with rough land (such as comfrey and white deadnettle) and hedgerow species (such as willow, hawthorn and blackthorn).

Recent research revealed that wild pollinators provide a much more important service to commercial crops than previously thought. Dicks’ report identifies opportunities for enhancing the environment for six species of wild bee including three species of bumblebee by sowing wild flowers and providing environments for nests.

She compiled and analysed data from a number of wildlife conservation and research organisations, including the Bumblebee Conservation Trust, to build an overall picture of the resources that these insects need to flourish.

By calculating the pollen demands of individual bees, and the resulting demand for flowers, Dicks has come up with some approximate figures in terms of the percentage of land and hedgerow needed to resource a healthy population of selected wild pollinators. Using a 100-hectare block of land as the basis for calculations, she estimates that the provision of a 2% flower-rich habitat and 1km flowering hedgerow will supply the six pollinator species with enough pollen to feed their larvae.

“We suggest that farmers sow headlands, field corners and other areas with mixes that will flower in the summer months, but they also need to manage hedgerows, woodland edges, margins and verges to enhance early and late flowering species and provide nesting and hibernating opportunities,” says Dicks. “It’s really important that the packages offered to farmers through the Countryside Stewardship scheme are easy to implement and well supported by financial incentives and advice. Because we are learning more all the time about the interaction between wild pollinators and the environment, schemes also need to have built-in flexibility.”

Next in the Cambridge Animal Alphabet: R is for an animal that is often found among the pages of children's literature.

Have you missed the series so far? Catch up on Medium here.

Inset images: Bombus pascuorum (Joan Chaplin); Bombus lapidarius (Tessa Bramall).

The Cambridge Animal Alphabet series celebrates Cambridge's connections with animals through literature, art, science and society. Here, Q is for Queen Bumblebee, one of the UK's 1,500 species of wild pollinators that play a vital role in the environment and food production.

We depend on pollinators for food production so it’s in our interests to halt drops in numbers
Lynn Dicks
Bombus pascuorum

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Love’s Labours: study shows male lizards risk becoming lunch for a bird in order to attract a mate

By jeh98 from University of Cambridge - Department of Zoology. Published on Sep 22, 2015.

In the animal kingdom, the flashiest males often have more luck attracting a mate. But when your predators hunt by sight, this can pose an interesting problem.

Like many species, lizards use bright colours for sexual signalling to attract females and intimidate rival males. A new study published in Ecology and Evolution by Kate Marshall from the University of Cambridge’s Department of Zoology and Martin Stevens from the University of Exeter’s Centre for Ecology and Conservation has provided evidence that this signalling comes at a cost.

Using models that replicated the colouration of male and female wall lizards found on the Greek islands of Skopelos and Syros, they found that the male lizard models were less well camouflaged against their habitat and more likely to fall prey to bird attacks.

Marshall, lead author of the study, explains: “we wanted to get to the origins of colour evolution; to find out what is causing colour variation between these lizards. We wanted to know whether natural selection favours camouflage, and whether the conflicting need to have bright sexual signals might impair its effectiveness.

“It has previously been assumed that conspicuous male colours are costly to survival, but this hasn’t been tested before among these specific lizards living on different islands, and in general rarely in a way that takes into account the particular sensitivities of avian vision.”

Birds see the world differently from you or I: they are able to see ultraviolet (UV) light whereas we cannot, which means they perceive colour (and camouflage) in a very different way. To test whether the males really are more visible to feathered predators, the researchers had to develop clay models that accurately replicated the lizards’ colour to a bird’s eye.

Using visual modelling, Marshall and her colleagues painstakingly tested around 300 colour variations to find ones that matched the male and female colours in order to make the 600 clay lizards used in the study.

Marshall comments: “it was important to get a clay colour that would be indistinguishable from a real lizard to a bird’s eyes: we even tried using a paint colour chart, but they all reflected too much UV. To us the models may not look like very good likenesses, but to a bird the models should have looked the same colour as the real lizards.”

Marshall and her field assistant, Kate Philpot, placed the male and female lizard models in ten sites on each of the two islands and checked them every 24 hours over five days to see which had been attacked by birds.

“The models that had been attacked showed signs of beak marks, particularly around the head, and some had been decapitated,” explains Marshall. “We even found a few heads in different fields to the bodies.”

“The fact that the birds focused their attacks on the heads of the models also shows us that they perceived them as real lizards because that is how they would attack real prey,” she adds.

At the end of the study, the researchers found that the models with male colouration had been attacked more than the models with female colouration.

Marshall and the team also tested how conspicuous the models were against their real backgrounds using further modelling of avian vision, and found that the male models were less camouflaged than the females.

“In females, selection seems to have favoured better camouflage to avoid attack from avian predators. But in males, being bright and conspicuous also appears to be important even though this heightens the risk of being spotted by birds,” says Marshall.

However, it is not entirely a tale of woe for the male Aegean wall lizard. Despite being attacked more than the females by predatory birds, 83% of the male lizard models survived over the course of the five-day experiment. Marshall explains that this may indicate that males have colour adaptations that balance the contradictory needs to attract a mate and to avoid becoming lunch.

“In past work we’ve found these lizards have evolved bright colours on their sides, which are more visible to other lizards on the ground than to birds hunting from above,” explains Marshall. “The visual system of lizards is different again from birds, such as through increased sensitivity to UV, so the colour on their backs is more obvious to other lizards than to birds. Such selective “tuning” of colours to the eyes of different observers might provide at least some camouflage against dangerous predators that sneakily eavesdrop on the bright signals of their prey.”

“With these models we were only able to replicate the overall colour of the lizards rather than their patterns, so it would be interesting to investigate further whether these patterns affect the survival rates of lizard models,” she adds. “It would also be great to apply this type of experiment to other questions, such as how different environments affect the amount of predation that prey animals experience.”

Reference: Marshall, K et al. “Conspicuous male coloration impairs survival against avian predators in Aegean wall lizards, Podarcis erhardii” Ecology and Evolution (September 2015). DOI:

The research was enabled by funding from the Biotechnology and Biological Sciences Research Council, the British Herpetological Society, the Cambridge Philosophical Society, and Magdalene College, Cambridge.

Inset images: Tetrahedral plot of avian vision (Kate Marshall et al); Models showing signs of bird attack (Kate Marshall et al); Males, females and their corresponding models (Kate Marshall et al).

New research shows male lizards are more likely than females to be attacked by predators because the bright colours they need to attract a mate also make them more conspicuous to birds.

The models that had been attacked showed signs of beak marks, particularly around the head, and some had been decapitated
Kate Marshall
Female (left) and male (right)

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Tom Evans awarded the John Ray Science Prize 2015

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