So, ARE there limits to evolution?

St John's College

St John’s College

Cambridge plays host to many meetings each year but few as unique and ambitious as the “Are There Limits to Evolution” conference that took place over two sunny days this September. Professor Simon Conway Morris and his team from the Department of Earth Sciences at Cambridge organized the conference, which was set in the scenic and stimulating backdrop of St John’s College. Nearly 30 speakers from all over the globe and from many different scientific disciplines shared their answers to the deceptively simple question: Are there limits to evolution? Speakers and delegates alike were rigorously challenged and enjoyed being part of a fascinating effort to articulate the key areas of research that will define the future of evolutionary biology.

conf_venueProfessor Simon Conway Morris commented that “All conferences have something new, but this one was special both because it brought together an extraordinary cross-section of leading scientists, from physicists to biologists, and because it looked to the problems rather than the solutions. That is a rare synergy.”

The conference schedule took all attendees on a rollercoaster for the brain, with speakers engaging their audience on subjects as diverse as burrowing mammals, prokaryote evolution, Neanderthals, protein evolution, cichlid fishes, homology, self-domestication, protein evolution, animal symmetry, convergence, cosmology, technology, ergodicity and Newtonian limits.

Dr Victoria Ling

Dr Victoria Ling

Dr Victoria Ling, an expert in anthropology and science communication, ran the conference and in parallel a series of interviews with key speakers. These interviews allowed the team to record the opinions of leading biologists, philosophers and physicists on the future of evolution, as well as aspects of their life stories as scientists. Footage was skilfully shot by Peter Harmer and Mark Jones and will be available to view on a new explorative website being created in partnership with The District and to be launched in 2015. Watch this space (and follow Map of Life on Twitter or Facebook) for updates.

Convergence at the conference

Although hard to choose just a few, highlights from the conference that relate to convergent evolution are given below:

Conference dinner at St John's College

Conference dinner at St John’s College

Eugene Koonin’s research on the fluid genomes of prokaryotes includes finding independent origins for three groups of giant viruses of prokaryotes. Virginie Orgogozo looked at changes in large effect genes of known function between closely related species, and found lots of convergent ‘genetic plagiarism’ (e.g. optix genes in Heliconius butterflies and lateral transfer of carotenoid genes in pea aphids and spider mites). George McGhee explored the limits on helical bryozoan colony form, showing how the key adaptation of water filtration efficiency poses a limit on colony form, as observed in the fossil record. Robert Asher focused on burrowing mammals, a dispersed group including the widespread talpid moles, golden moles of Africa and marsupial moles of Australia. The remarkable hearing of golden moles is based on inner ear specialisations that while beneficial when burrowing, limit colonization of aquatic habitats. conf_signWalter Salzburger mentioned some of the most striking cases of convergence among the iconic cichlid fishes, a group known for astonishing and yet constrained diversification. Geerat Vermeij, Russell Powell and others pointed in different ways to the general need for understanding the contraints on development when assessing convergent traits at different levels in the tree of life. Jonathan Losos expanded the classic case of convergence provided by Anolid lizard ecomorphs (link to Mol) by showcasing the truly convergent lizards alongside a few unique anoles that add questions about contingency, constraint and novelty in ecosystems. Josh Mylne described an incredible instance of protein convergent evolution based on research into a sunflower gene (PawS1) encoding a precursor seed storage protein. PawS1 contains a sequence for a trypsin-inhibitor (SFTI-1) with a cyclic inhibitor motif also found in distantly related legumes, cereals and even frogs.

Humanity and limitations

the_div_schoolWhat of the hot topic of human evolution? Anders Sandberg and Geerat Vermeij both pointed out that humans today effectively exist apart from natural selection and that as intelligent agents with technology we can change the ‘goals’ of evolution. Chrisantha Fernando described how neurons and networks in the brain appear able to learn and evolve, showing varied degrees of plasticity. Peter Kjaergaard shared research into the many origins, Neanderthal and otherwise, of today’s Danish population. Richard Wrangham described a model connecting incomplete development of so-called neural crest cells with a syndrome of traits related to selection for reduced aggression (domestication). He suggested that humans are self-domesticated, with certain traits such as smaller brains, less male-female dimorphism and lifelong learning being inextricably tied to the selected trait of reduced aggression as our species evolved to co-exist in great numbers.

For the record

conf_schedule_pagesKey speakers were Gunter Wagner, Eugene Koonin, Virginie Orgogozo, Matthew Wills, L. Mahadevan, Tom McLeish, George McGhee, Anders Sandberg, Eörs Szathmáry, Peter Kjaergaard, Mark Maslin, Ard Louis, Jennifer Hoyal Cuthill, Halló Gabor, Geerat Vermeij, Robert Asher, Sylvain Gerber, Walter Salzburger, Russell Powell, Tristan Stayton, Chrisantha Fernando, Jonathan Losos, Richard Wrangham, Michael Hendy, Josh Mylne and Peter Robinson. All agree that, yes, there are limits to evolution, and that there is still much to explore to define and understand the constraints and patterns of evolution. Thanks to the speakers and all the other participants for making the conference a unique and productive event.

Want to know more?

If you’d like to treat your brain to an array of angles on evolution, a few books recently published by key participants at the conference include:

And finally, if you would like to immerse yourself in everything human evolution, Peter Kjærgaard and others are delighted to announce the very recent opening of the new Moesgaard Museum in Denmark. Map of Life already loves it…

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An asymmetric diet of snails

One of the new entries on the Map of Life highlights some of the extraordinary convergences relating to snake and lizard feeding. Perhaps the most charismatic example relates to some beautiful neo-tropical snakes who have become truly adept at extracting snails from their shells and scoffing them at will. Here is a taster (as it were) and do head over to our “Feeding in snakes and lizards” entry for even more to chew on…

Snails may not be everyone’s first choice on the menu but several distinct colubrid snakes have evolved expert techniques for gorging on these nutritious gastropods. Southeast Asian pareatine snakes (e.g. Pareas iswasaki) and neo-tropical dipsadine snakes (e.g. Dipsas) both have asymmetrical mandibles (lower jaws) with many more teeth on the right than the left side.  

Catesby's snail-eating snake, photo by G. Gallice

Catesby’s snail-eating snake, photo by G. Gallice

The right and left mandibles are inserted into right-coiling snail shells and then by repeated and alternate retractions, they delicately extract the snail’s soft body. In an incredible instance of convergence, not only the pareatine and dipsadine snakes, but also certain insectivorous beetle larvae also have asymmetrical mandibles for snail predation. Because the right-coiling snails are preferred this  means that the much rarer atypical left-coiling variants can gain a selective advantage where these predators abound.

Still within the reptiles we find another highly adapted snail-eater and with it another exemplary case of convergence. The Australian pink-tongued skink (Cyclodomorphus gerrardii) is a rainforest-dwelling lizard with a pair of large ‘hammer’ teeth for cracking snail shells. Within the same geographic region fossils of a Miocene marsupial (Malleodectes) have been found whose dentition is all but identical to Cyclodomorphus. It seems that both animals preyed on rainforest snails in the same way, and in the increasing competition resulting from climate change the lizards, in the end, came up trumps.

 

Posted in Convergence

How is a sea urchin like an insect eye?

EchinometraSea urchins and starfish may not be the first creatures that come to mind when pondering animal eyes, but they are full of surprises. Many echinoderms (sea urchins, starfish, brittle-stars, sea cucumbers and sea lillies) are sensitive to light. Certain brittlestars (the ophiuroids) and sea urchins (the echinoids) even have compound eye-like visual systems that in some ways rival the arthropods. So it is that along the arms of one brittlestar (Ophiocoma wendtii) we find calcitic ‘microlenses’. These are composed of modified ossicles, can be shaded using pigmented chromatophore cells, and are underlain by the photoreceptors. In sea urchins visual acuity appears to be based on photoreceptors in the tips and bases of tube feet, and here shading is not mediated by protective pigments but rather by skeletal elements (spines and tube foot pores). Visual acuity of these animals apparently approaches that of the speedy predator Nautilus.

Ophiocoma_scolopendrinaAs echinoderms have a diffuse nervous system rather than a defined brain it is not clear what sort of image the animal may ‘see’ and yet their eyes provide fascinating points of convergence. For example, the calcite microlenses of brittlestars closely resemble those found in the compound eyes (the schizochroal variety) of certain trilobites. Furthermore, the way that the sea urchin tube foot system gathers visual information parallels the structure and function of the insect compound eye in interesting ways.

Head over to the latest entry on echinoderms at the Map of Life to read the full account of this strange case of convergent evolution! You may never look at a sea urchin again in the same way…

Posted in Convergence

Hunt for eggs and be the science behind camouflage

egglab3Ever wanted to hunt for digital eggs instead of chocolate ones at Easter? Perhaps not, but here is a brilliant online game about hunting for nightjar eggs that is both fun and calorie-free! Do have a go and be a valuable part of an experiment in the evolution of camouflage.

http://nightjar.exeter.ac.uk/egglab/ 

The game (EggLab) is part of Project Nightjar, a study of camouflage run by Dr Martin Stevens of the Sensory Ecology Group at the University of Exeter (Cornwall Campus), in collaboration with the Behavioural Ecology Group at the University of Cambridge. The study focuses on ground nesting birds like nightjars, including their well-camouflaged eggs…

egglab1EggLab may be an Easter egg hunt with a difference but it’s also a genuine science experiment to find out how types of camouflage can evolve in different habitats. The game is based on three species of nightjars who each like to lay their eggs in different places – from open habitats to leaf litter. Populations of eggs on different backgrounds (sand, grass, soil, leaves etc.) evolve colours and patterns over time, based on how speedily they are spotted by the egg-hunters. egglab2

For Project Nightjar’s eggs to have a chance to evolve, effectively matching the habitats they are laid in, a lot of people need to play the game! Do have a go yourself  (it takes less than a minute to hunt out one batch of eggs) and please pass this on to anyone you know who would enjoy a bit of fun and being a real part of science, over Easter and beyond. Every egg counts!

You can follow Project Nightjar Twitter and check in out on Flikr. The Sensory Ecology Group is also on Facebook, Twitter and YouTube. Map of Life is also on Facebook and Twitter – follow us for convergent evolution and more.

Posted in Education, News, Research

Highlighting the Tree of Life

onezoomAre you interested in the ins and outs of how organisms are related to each other? The Map of Life has recently discovered a new ‘explorer’ tool that allows fascinating adventures amid the winding branches of the Tree of Life. You can find out for yourself at OneZoom.org and we especially recommend a visit if you are interested in getting lost in plant, bird or mammal evolution for these are the main focus. An exciting new project and a great tool for highlighting many of the convergences detailed on the Map of Life.

animaltreeThinking of the Tree of Life reminds us to flag up the various illustrated Tree of Life diagrams that you will find at the Map of Life. You can click to these helpful illustrations of organism relationships at the bottom of every page on the Map of Life. Do take a peek at http://www.mapoflife.org/about/tree_of_life/

You’ll find beautifully illustrated diagrams (‘trees’) showing the relationships among plants, animals, eukaryotes (everything with a nucleus) and an overall tree for all living things. Enjoy!

blue_agaveWithin many of the Map of Life topics you will find tree of life diagrams as well, summarising where the convergence occurs and just how distantly related are the organisms being reported. For example if you have ever wondered why desert plants look amazingly similar in the Americas and in Africa, or ever mistaken an Agave for an Aloe (easily done!) then head over to our topic on “Succulent desert plants“. There you’ll find lots of info on these marvellous plants and a tree diagram showing where in the plant tree of life they fit in.

Posted in Convergence, Education

Are there limits to evolution?

Are_there_limits_to_evolution_posterWhat will evolutionary biology look like in 50 years? More of the same or will there be new paradigms, new syntheses? What lies on the horizon?

The impact of evolution is undeniable, but it can be viewed through different lenses. For the scientist it is the investigative discipline, mapping out the history of life, uncovering its intricacies and revealing its mechanisms. For others it might be the grand narrative, and across society it brings different meanings—sometimes to the point of polarization. Ideas about evolution pervade and influence our self-understanding. Image mosaicThis was evident throughout the celebrations in 2009 of Darwin’s bicentennial and The Origin of Species’ 150 years. Yet the subject of evolution is not merely “Darwinism”, let alone “neo-Darwinism”, but a science that ought always to seek new questions, rattle the cage of existing paradigms and not rest content with received wisdom.

In September 2014 in Cambridge a conference will be held focusing on the important research objectives in evolution, discuss the best ways to achieve them, and use these to set a considered agenda for the continued study of evolution. What are the questions we now need to define? For instance:

  • Can we define biological complexity? Are there limits to complex systems?
  • How do biological systems integrate? How do horizontally transmitted genes become incorporated into the genome?
  • What is the significance of mosaic evolution?
  • Is evolutionary convergence ubiquitous? If so, is this of any wider significance?
  • How soon before we detect habitable planets and what is the significance for exobiology?
  • What is the nature of consciousness, and in the context of neuroscience are there any compelling explanations?

If you might be interested in joining this conference, or following its progress click here to find out more!

Posted in Events, News

Aurornis xui: a new piece in the bird evolution puzzle

feather_ArchaeopteryxAs more and more stunning feathered reptile fossils are unearthed in China the tale of the origin of birds and the evolution of flight becomes more and more complicated. Did powered flight, as in the birds, evolve once only or does it represent one of the most astonishing examples of convergence yet reported? A new analysis of a Jurassic bird-like dinosaur named Aurornis xui may shed some new light on the story.

Aurornis_xuiArchaeopteryx, known from Jurassic rocks around 150 million years old is the best known candidate for earliest primitive bird, at the base of the lineage leading to today’s ‘true’ birds (Euornithines). This iconic status has been shaken up with the discovery of feathered paravian (bird-like) dinosaurs that appear to be primitive birds very much like Archaeopteryx but may be around 10 million years older. Godefroit et al. recently presented Aurornis xui and suggest that it and its relative Anchiornis precede Archaeopteryx in the Avialae – the group that leads to and includes the true birds. This destroys Archaeopteryx‘s position as the earliest bird and, in their new grouping of avialids, infers that powered flight using feathered forearms only evolved once. So much for convergence? Perhaps, but then again perhaps not. Read on for a few highlights from the complex debate…

A rich diversity of feathered reptiles is now known to exist, particularly from Late Jurassic and Early Cretaceous fossils of China. These reptiles belong almost exclusively to the Paraves, a group that includes Deinonychosauria (dromeosaurs such as the famous Velociraptor and troodontids) and also Avialae. Feathered forewings are common to all paravians (even the hefty Velociraptor has quill knobs for long feather attachment) and many deinonychosaurs also show feathered hindwings. Primitive paravians (e.g. Eosinpteryx), dromeosaurs and troodontids could not fly; perhaps their feathers evolved through sexual selection, as adaptations for display. Microraptor_fossilIt seems clear that, in addition to a bipedal gait, the transformation of scales into pennaceous feathers was indeed a pre-requisite for flight, but feathers also occur in a huge diversity of non-flying lineages.

One interesting evolutionary pattern among the pre-avialids is the appearance, in the dromeosaurs, of species with well developed hind-wings. Microraptor gui is a key example here, being described as capable of bi-plane style of gliding, with a U-shaped glide trajectory like certain gliding mammals. Gliding feathered reptiles evolved by convergence earlier in reptile history; Longisquama insignis is a Late Triassic archosaur whose feathers are different in structure than those of Microraptor; not surprising given that it is very distantly related. Longisquama‘s discovery sparked  debate about possible convergent evolution of feathers and even of birds.

While Godefroit puts all the powered fliers in one avialid group certain members of his proposed lineage are still disputed. For example, other analyses placed Aurornis and Anchiornis in the adjacent group Troodontidae,  and another supposed avialid named Xiaotingia, some believe could be a primitive dromeosaur. The clumsy flier Rahonavis is generally accepted to be an early bird, and yet some argue that it belongs with the dromeosaurs, again indicating possible convergent evolution of forearm-powered flight and ‘birds’. Archaeopteryx_lithographicaWork by Xu et al. in 2011 even places Archaeopteryx outside the Avialae, supporting a possible double origin of powered flight.  The intense diversification of feathered reptiles evident from the Late Jurassic to Early Cretaceous makes the hunt for solid answers a tough challenge.

Given the clear ecological advantages of powered flight, perhaps it is hardly surprising that evolution found a way to put a number of reptiles, the insects and even bats into the skies. Whatever the relationships among the bird-like dinosaurs turn out to be, at the largest scale of the tree of life the evolution of flight remains an inspiring case of convergence at its most fundamental.

Posted in Convergence, News, Research