Features

All this week we're celebrating Darwin and the advances in evolutionary theory that have built upon his work.

I asked Aris Katzourakis of Oxford's Department of Zoology about the evolutionary 'arms race' between viruses and us:

OxSciBlog: How does studying virus evolution compare to studying the evolution of larger organisms?
Aris Katzourakis: Virus evolution occurs over far shorter time frames, and can be observed on the molecular level. For example, for rapidly evolving RNA viruses like HIV or Hepatitis C, evolution can be observed during the course of an infection within a single patient, while for the Influenza virus, evolution can be observed within the human population over the years. This offers unique opportunities to study evolution in real time, while also enabling predictions about the course of viral evolution that can be applied in a public health setting.

OSB: What makes the evolution of viruses such as lentiviruses and HIV/AIDS so challenging to unravel?
AK: The lentiviruses are locked in an arms race with the immune systems of their hosts, meaning that both parties are constantly changing in order to adapt to new challenges. This effect has been called the ‘Red Queen’ effect in evolutionary biology, in reference to the statement by the character of the same new, from Lewis Carroll's book - “It takes all the running you can do, to keep in the same place”. In practical terms, this means that the genomes of lentiviruses are constantly changing, and we are still a long way from unravelling all the pressures exerted upon the virus by the immune systems of their mammalian hosts.

OSB: What does research into lentiviruses suggest about their possible future evolution and that of HIV/AIDS?
AK: Recent research from studies of endogenous lentiviruses has shown that the lentiviruses are far older and more widespread among mammals than has been previously appreciated. This implies that there may be more lentiviruses that remain undiscovered in the wild, that could potentially make the leap from infecting other mammals to infecting people. Furthermore, the realization that lentiviruses are millions of years old implies that the corresponding conflict with their hosts immune systems has been played out over this period of time. Perhaps there remain undiscovered host innate immune factors in mammalian species, resulting from this ancient conflict, that could be harnessed in the fight against HIV.

OSB: What technological advances on the horizon could transform studies of virus evolution?
AK: Ever cheaper and more rapid sequencing will undoubtedly greatly expand our knowledge of virus evolution. Coupled with this, advances in computational techniques required to make sense of this data will prove instrumental. Many exciting discoveries in virology have occurred from the most unexpected places - I suspect the most important findings of the coming years will come as a surprise to researchers in the field of virus evolution.

Dr Aris Katzourakis is based at the Department of Zoology and the Institute for Emergent Infections, James Martin 21st Century School.

Read more of our Darwin special: worms & vertebrates, humanity's roots, birds, beaks & species

All this week we're celebrating Darwin and the advances in evolutionary theory that have built upon his work.

I asked Joseph Tobias of Oxford's Department of Zoology about birds, their traits, and how they evolved:

OxSciBlog: Darwin was fascinated by finches: What is it about birds that makes them ideal case studies for evolution?
Joseph Tobias: Viewpoints differ, as always. One regularly hears that birds are not ideal systems for evolutionary research. Listen to any entomologist or bacteriologist, for example, and they will tell you that birds are too much work to keep in the lab, or too slow to reproduce. A botanist will add that wild birds wake up impossibly early and move around too much. An ornithologist, however, will point out that birds make rewarding subjects because they can be studied in natural settings, and they offer several key measurable traits.

Some of these traits - including the number of eggs produced in a clutch - are associated with life-history, while others are linked to ecology. The beak, for example, is the main foraging apparatus of birds, and therefore strongly shaped by diet. Variation in beak design is a feature of adaptive radiations, as was evident in Darwin’s collection of finch specimens from the Galápagos, thus providing an inspiration for the theory of natural selection. Similarly, elaborate plumage ornaments and complex songs were central to the development of Darwin’s 'other theory', sexual selection.

Beaks, plumes and songs continue to be mainstays of evolutionary research. Meanwhile, birds have also made a disproportionate contribution to our understanding of behaviour as an agent of selection, partly because wild birds are easier to catch, mark, track and observe than many other animals.

To some extent, the role of ornithology as a driving force within evolutionary biology can be boiled down to the fact that birds, like us, are audio-visual creatures with acute colour vision and mid-range hearing. From a signalling perspective, they speak our language, and this explains a large part of their allure.

OSB: What can birds tell us about Darwin's 'mystery of mysteries', the origin of species?
JT: One upshot of the popularity of birds is that we know lots about them, and this simple fact accentuates their importance for studies of speciation. We have at our disposal more information about species limits, global ranges, ecological niches, and life-history strategies for birds than for any other diverse group of animals or plants. The same can be said of sequence data, as a flood of phylogenetic studies is rapidly filling out the avian tree of life. Given that the molecular clock is relatively consistent in birds, biologists can use these sequence data not only to determine the relationships between the branches of the tree but to estimate the timing of evolutionary events, including speciation. By putting these resources together, and applying increasingly powerful computational methods, it is becoming possible to test previously intractable hypotheses about the factors promoting reproductive isolation and shaping patterns of diversity.

Genetic data have already taught us more in the past decade about the way lineages diversify than we learned in the other 190 years since the birth of Darwin. The good news is that this exhilarating period of discovery is set to continue, with birds as a common theme.

OSB: What have your studies of Amazonian birds revealed about the evolution of signals?
JT: Most Amazonian birds have simple, genetically determined songs. By quantifying their structure, and conducting experiments to test perception, we are investigating how these signals are shaped by ecology and interactions.

For example, we have found that songs of different species are adapted to the transmission properties and noise regimes of their respective microhabitats. Whether by this kind of ecological adaptation or by random mutation, the process of signal divergence in isolated forest patches can be fairly rapid: a few thousand years can produce enough difference in song structure to reduce responses between populations. On the other hand, we have found compelling evidence that interspecific competition can drive convergence in territorial songs, suggesting that social selection can operate across species boundaries.

Further work on dueting species has shown that temporal coordination in joint signals is promoted by intersexual conflict rather than, as commonly assumed, cooperation. These are a few examples of how a comparative and experimental approach can clarify the mechanisms underlying speciation and phenotypic evolution.

OSB: How might research into evolution help in the conservation of rain-forest species?
JT: Some apparent flaws in current conservation practice can be attributed to a species-based mentality. This means that, in deciding what we want to conserve, we use as our currency a system of units that represent a mere snapshot of evolution, and which in any case we find impossible to define. Of course there will always be powerful flagship causes like pandas and whales, but evolutionary biology and conservation genetics can expand our consciousness beyond the ‘species’.

These disciplines encourage a consideration of the longer view, and of process rather than pattern. They highlight the importance, for example, of connectivity between habitats rather than isolated reserves. They reveal the remarkable genetic diversification within rainforest ‘species’, and draw attention to zones of future evolutionary potential. The pattern-based view directs resources towards the conservation of island faunas, where populations are naturally rare and often short-lived, whereas the evolutionary view argues for the re-direction of some of those resources to continental habitats, and to rainforests in particular. These are the powerhouses of terrestrial evolution, but they will only continue to function as such if we succeed in maintaining them at something like their present size.

Dr Joseph Tobias is a Departmental Lecturer in Evolutionary Ecology at Oxford’s Department of Zoology.

Read more of our Darwin special: worms & vertebrates, humanity's roots

All this week we're celebrating Darwin and the advances in evolutionary theory that have built upon his work.

Darwin famously delayed his masterwork, On the Origin of Species, over concerns about how it would be received.

He was right to be worried. The implications of his theory of evolution by natural selection undermined established beliefs about humanity's special place in the world and turned man into just another animal - with apes for cousins and worms for ancestors.

It provoked hostility at the time and has been used since to justify everything from colonialism and class warfare to the holocaust. So how should we think about human evolution now?

'These negative associations are not really valid as evolution is not a political vehicle facilitating forms of cultural over-lordship but rather an unconscious force applicable to the entirety of our species,' Oxford's Timothy Clack, who studies archaeology and biological anthropology, told me. ' We are all Homo sapiens and all share the same evolutionary history.'

Driven to destruction?
Timothy believes that our evolutionary drives are at odds with our modern way of life and this conflict is having a dire effect on our physical and mental health, as well as the environment:

'Rates of diabetes, obesity, heart disease and high blood pressure soar because our bodies are unfit for purpose in environments where we consume vast amounts of fat and carbohydrate and levels of physical activity are in decline. We have insatiable appetites for high-calorie foods because in the evolutionary past they were rare and on those infrequent occasions when they were encountered, for example on finding a honey-rich beehive or a clutch of bird eggs, it made sense to gorge oneself. Unfortunately there is no off-switch and the availability and low-cost of these food items nowadays results in their over-consumption.'

The other problem is that we no longer behave like the hunter gatherers we evolved to be and burn off any excess calories: stamina and an athletic frame are hardly necessary to hunt down food in your local supermarket. 

It's not just physical, according to Timothy humans also miss out on the rich and long-lasting social bonds fostered in tight-knit hunting bands of up to 100 members. He comments: 'Real friendships are in shorter supply than ever before because our geographic mobility, frequent relocations, endless commitments and levels of exhaustion deny us the time necessary to develop them. '

Under the influence
Yet despite this mismatch our inherited evolutionary drives remain very powerful and are used by everyone from advertisers to politicians to influence us.

Timothy explains: 'Models are used to promote things because we respond positively to attractive people. By playing on our evolutionary disposition good advertising helps us accept that any particular product is sexier, newer and better than the competition. We learn that status is enhanced with possession. At the same time consumerism is linked to our compulsion for territorial marking and resource acquisition; both of which are important for attracting mates.'

'Both the sexes have voyeuristic predispositions and these evolved on the savannah at a time when sex was a public enterprise. We may have placed intercourse modestly behind the bedroom door but flirting and other performances of attraction still take place in the open. Sex appeal has taken on greater significance in the modern media culture where the image has replaced the word as the primary means of communication. Politicians are getting younger and more attractive because these qualities correlate with sex appeal. We generally afford the good-looking more trust and confidence.'

Going against Nature
So is the battle against our evolved instincts hopeless?

'The good news is that not all of our evolutionary heritage is harmful. Certain qualities like innovation, emotion, empathy, sociality and language can be embraced. The bad news is that the more negative traits will be difficult if not impossible to shake. There is a little room for optimism, however, for in recognising negative traits we can strive to mitigate their impact.'

'Natural selection may have been the human architect but thanks to the many adaptations it implanted we find ourselves in pretty exceptional territory. Our self-awareness and ability to comprehend the evolution and future of our species uniquely places us to resist impulses and drives. Culture bestows on us the means to refrain from antisocial behaviours, even those that may have some fashion of evolutionary basis. In certain locations over the course of three generations we have seen major steps in the fight against racial segregation, sexual inequality and religious persecution. Therefore we must not deploy evolution as an excuse for in doing so we legitimise the worst of our character.'

Dr Timothy Clack is the author of Ancestral Roots a book exploring the links between modern day problems and our evolutionary past.

Read more of our Darwin special: worms & vertebrates

All this week we're celebrating Darwin and the advances in evolutionary theory that have built upon his work.

I asked Peter Holland of Oxford's Department of Zoology about early vertebrates, worms and us:

OxSciBlog: How has genomic science changed how we think about evolution?
Peter Holland: Genomics hasn’t changed the way we think about evolution at a fundamental level – I mean, even before genomics we knew that evolution is a fact consistent with all biological knowledge, that all life on earth diversified from one origin, and that the dominant forces underpinning evolution are mutation and selection. But what genomics has done is added colour and detail to that picture.

For example, sequencing of genomes has given us new insights into the different types of mutation, not only small changes to individual genes, but big mutations that copy whole sets of neighbouring genes in tandem, or duplicate entire genomes.

And we should not forget the technological advances that genomics has driven, such as faster, cheaper DNA sequencing. This now enables researchers to deduce the past history of life on earth using hundreds of genes at a time, not just one or two, with some major new insights into the true tree of life.

OSB: How far back can we trace the basic body plan of vertebrates?
PH: All vertebrates share the same fundamental body plan, with a complex head built from moving ‘neural crest’ cells, a subdivided brain, segmented blocks of muscle and a skeleton of some sort. Only vertebrates have all these features together, and even the oldest vertebrate fossils show signs of them.

Interestingly, when we look at our closest non-vertebrate relatives (amphioxus and sea squirts) we find some of these features in rudimentary form, implying that the extinct vertebrate ancestors also had these rudimentary structures.

So when the first vertebrates evolved, perhaps 550 million years ago, evolution just elaborated on what was already present, by adding some new cell types such as bone, cartilage and an adaptive immune system.

OSB: Why, in terms of evolution, are genome duplication events important?
PH: In 1882, the satirical magazine Punch published a cartoon about Darwin entitled ‘Man is but a worm’. We now know that actually ‘Man is but four worms’, because at the origin of vertebrates the whole genome – every gene – was duplicated twice. Many of the extra genes were lost after this event, but vertebrates still retain more genes than most invertebrates.

It is tempting to suggest that these extra genes were recruited for new roles, allowing new tissue and cell types to evolve, and in fact there is evidence to support this hypothesis.

However, this does not mean that genome duplications are always associated with adaptation – for example, the squid and octopus lineage evolved anatomical complexity without genome duplication, while teleost fish experienced a genome duplication without obvious increase in complexity.

OSB: What major questions about the evolution of early vertebrates remain to be answered?
PH: We don’t have a good handle on the timeframe – we need more fossils to give us better dates. We also don’t fully understand how new genes gain new roles, and this is notoriously difficult to study. And finally it has been difficult to work out how lampreys and hagfish fit into the history  – did they branch off before the two genome duplications, after, or in between? This last point has spawned many heated discussions!  

Peter Holland is Linacre Professor of Zoology and Associate Head of the Department of Zoology at Oxford.

To most people the idea that ants communicate using sound is pretty surprising.

So how much more surprising is that these ant sounds (in particular queen ant sounds) are mimicked by the pupae and caterpillars of an ant parasite: the Rebel's Large Blue butterfly?

As The Times, amongst others, reports this is exactly what a team including Oxford's Jeremy Thomas have demonstrated in research published in this week's Science.

The original idea came to Jeremy some 15 years ago when he was recording the stridulations of worker ants and caterpillars and noticed similarities between calls of certain species. He realised that these sound signals might explain his observation that sometimes worker ants treated the caterpillars like ants queens when the caterpillar's chemical and behavioural signals only mimicked those of ordinary ants.

However, it would be over a decade before audio equipment was sophisticated enough to prove whether or not the idea was correct. 

The team tested the theory by recording and then playing back the sounds made by queen ants to workers in a nest. Jeremy told Lewis Smith in The Times: 'When we played the queen sounds they did 'en garde' behaviour. They would stand motionless with their antennae held out and their jaws apart for hours - the moment anyone goes near they will attack.'

In short, the right sound signals cause workers to protect and care for an invading caterpillar as if it is their queen.

Such a discovery is especially important because the Rebel's Large Blue (Maculinea rebeli) is an endangered species, Jeremy notes: 'The new findings will play a key part in designing a successful science-led conservation strategy... Any such strategy must be based on an excellent understanding of the intimate interactions between the butterfly and its ant host.'

'There is also an urgent need to investigate whether acoustical mimicry has evolved among other, rare, social parasites that infiltrate and exploit ant societies.'

Professor Jeremy Thomas is Professor of Ecology at Oxford's Department of Zoology and a Professorial fellow of the Centre for Ecology & Hydrology

The work was carried out by researchers from Oxford University, the Centre for Ecology & Hydrology and scientists from the University of Turin, Italy.