Friday, 17 February 2017

The science behind the movie: what we really know about dinosaurs and how

This is an article that I wrote to accompany a lecture I gave at the Royal Albert Hall, back in November 2016, in conjunction with some screenings of Jurassic Park that were accompanied by a live orchestra. For various reasons, this didn't get published and I just found it again and thought I might as well pop it on here ...

The premise underlying the Jurassic Park franchise is an elegant one: that dinosaur DNA, preserved in the guts of ancient mosquitoes trapped in amber, could be used to clone these animals, bringing them back to life using the latest genetic technology. A terrific idea, but, sadly, one that remains deeply within the realms of science fiction as - to date - no-one has discovered even a fragment of dinosaur DNA, nor do we currently have the means to clone a dinosaur even if we were lucky enough it’s original genetic material. More hopefully, some scientists are attempting to bring back other famous animals from extinction, including the iconic woolly mammoth. Mammoths are lot younger than dinosaurs, having gone extinct only a few thousand, rather than millions, of years ago, and this means that many of their remains, frozen in Siberian permafrost, can yield large amounts of viable DNA for scientists to work with. However, even in this case a cloned mammoth is still a long way off. In addition to the numerous ethical problems that would surround the resurrection of an extinct species (the world has changed significantly since the last mammoth drew breath), there are still numerous scientific obstacles to mammoth cloning, not the least of which is that we have yet to learn enough about the reproduction of those animals that would be the best hosts for implanted mammoth embryos – elephants. So, given that we’re unlikely to see dinosaurs roaming our zoos and safari parks anytime soon, how do scientists determine how these amazing animals fed, ran, bred and died?

Palaeontologists, the scientists that study extinct life, have a surprising array of tools with which they can examine the fossilized remains of animals and plants to determine how they might have appeared and behaved when alive. In the case of dinosaurs we have their skeletons, but we also have other evidence that can give deep insights into their daily lives, including preserved gut contents, eggs, nests, footprints, skin impressions and even dinosaur poo. Detailed examination of skeletons provides information on the shapes of the bones and how they fit together. Comparisons with living animals are also key, as if we can identify similar features in these living animals, whose biology we can study in real time, we can then infer similar functions for those same features in extinct animals. Rough patches and flanges on bone can be used to reconstruct the positions of muscles, cartilage and ligaments, and studying the scratches and wear patterns on teeth reveals vital information on diet and feeding. This type of work has been carried out since dinosaurs were first discovered, in the early eighteenth century, and continues to provide new results today. However, this classical approach has been expanded thanks to the advent of an array of modern technologies, pioneered in fields as disparate as medicine and engineering, which are now being applied to fossils on an almost routine basis.

Perhaps the most significant of these advances has been the application of computed tomographic (CT) scanning. CT scanning uses rotating X-rays to build up a three-dimensional model of both the internal and external anatomy of an object and has diverse applications ranging from diagnostic use in medicine to checking car or airplane parts for flaws before they leave the factory floor. CT can be used to peer inside dinosaur bones and reveal features of the skeleton that were previously difficult to access, including the shapes of the brain and the air-filled sacs that ran through many dinosaur bones. The CT scans produce perfect virtual models of the bones that can then be subjected to testing in ways that would be impossible with a fragile or cumbersome fossil. By importing these virtual models into different computer programmes, dinosaur skeletons can be clothed in muscle, subjected to forces generated by walking, running and feeding, and tested to destruction in ways that no worthy museum curator would permit on the original bones themselves.

By carefully cutting thin sections through dinosaur bones and putting them under the microscope, we can age dinosaurs and work out how fast they grew to adulthood. This is done by counting the growth lines in the bone walls, which were laid down each year in a tree-ring like fashion. Dinosaurs grew really fast, with even the largest species reaching full size in no more than 30 years – and like humans dinosaurs had a teenage growth spurt. Some dinosaur fossils are so spectacularly preserved they include evidence of soft tissues like skin, muscle and internal organs, which give vital clues on dinosaur biology and appearance. For example, some spectacular fossils from China show that many meat-eating dinosaurs were covered in thick coats of feathers, helping to cement the idea that birds are nothing more than small, meat-eating dinosaurs that gained feathers and learnt how to fly. The recognition that birds are dinosaurs is an idea that has been proven beyond reasonable doubt in the last 20 years and also gives us new clues on what extinct dinosaurs might have been like. As living dinosaurs they can be used to test some of the ideas that palaeontologists have proposed based on bones alone. Moreover, they carry a direct genetic legacy of their dinosaurian ancestry, which means that bird genes are dinosaur genes, even though birds represent only one specialized branch of the dinosaur family tree. Some scientists are currently attempting to switch on long dormant genes in living birds that might have been responsible for producing the teeth, characteristic skull shapes and long tails of their dinosaur ancestors. These efforts are already producing impressive results, with genes being found that can transform bird beaks back into more dinosaur-like snouts and those that can stimulate hens to form teeth. Surprisingly, this work is not only interesting in its own right, but it has implications for human health as some of the key genes are also important in regulating various strains of human cancer, so this pure science project on dinosaur genes is providing insights that could improve human health too. Moreover, this type of genetic manipulation, based on the DNA of living dinosaurs, is probably the closest we will ever get in reality to a Jurassic Park scenario.

Saturday, 11 February 2017

Lake Kariba dinosaur expedition: Part 2

On arrival in Harare we were met by one of our local hosts, Dave Glynn, who whisked us to his house in the suburbs where were to meet the other team members. Dave and his wife Julie run a tourism business in Zimbabwe and organised most of the logistics for our trip, as well as hosting us before and after the fieldwork. They also provided our accommodation at Kariba, placing their houseboat on Kariba, Musankwa, at our disposal. As the day wore on, we were joined by Darlington Munyikwa, the Deputy Director of National Museums and Monuments, and Michael Zondo, from the Bulawayo Museum, both of whom have extensive fieldwork experience within Zimbabwe and had been on many trips to look for dinosaur material all over the country. All of us were to stay with Dave and Julie, to allow an early start on the road to Kariba. That night we were joined by more of the crew, namely the Broderick family, Tim, Patricia and Lucy. Tim was a geologist with the Zimbabwean Geological Survey and had spent many days walking and mapping our study area and his wife Patricia and daughter Lucy were veterans of many fossil hunting trips. Lucy is a professional photographer and was to prove invaluable in documenting our sites and finds. Over dinner we discussed our hopes for the trip and a strategy for making the most of our time around the shores of Lake Kariba.

After a short night and an early start, we packed our vehicles with field kit, 10 days worth of fresh food and other supplies, hitting the road at 4:30 am in order to reach Kariba by early afternoon. It was still dark as we left Harare, but as the sun rose it revealed a beautiful country. Most of the region between Harare and Kariba is farmland and the rains had left the landscape lush and green. After one minor breakdown, which was quickly repaired, we reached Kariba at lunchtime. The Broderick family caught up with us en route, bringing with them another team member, Rowan MacNiven, a fossil-mad restaurateur from San Francisco, whose loud and frequent shouts of “BONE!!!” would become a hallmark of the trip. 

Loading up the speedboats at Kariba and getting ready to cross the lake (photo: Pia Viglietti)

On arrival at Kariba we were met by the final member of our party, Steve Edwards, whose lodge, Musango Safari Camp, was based on the shores of the lake, in prime fossil-hunting territory. This is the point at which our work really began and the whole group was needed to transfer our supplies to the two speedboats that were to take us across the lake to rendezvous with Musankwa. We’d have these speedboats, and two other pontoon boats, with us for the entire trip to allow us to explore the convoluted coastline. With everything safely stowed we boarded and began the 90-minute journey westwards to meet Musankwa, which was lying moored off of the island that was to be the site of our first prospecting trip. The houseboat was essential as camping in the area is potentially hazardous, with lion, elephant, hippo and other game in the areas we wanted to prospect. In addition, it allowed easier transport of stores and was an excellent mobile base for moving from island-to-island and from lake-to-shore.

Some days the commute to work is a lot more pleasant than others (photo: Pia Viglietti)

During our journey across the lake we got our first real flavour of the region. Lake Kariba is one of the largest artificial lakes in the world and is 140 miles (~220 km) long, up to 20 miles (~32 km) wide and has a maximum depth of just under 100 m (although most of it is significantly shallower). It was formed by damming the eastern end of the Kariba Gorge, which forms part of the Zambezi river valley, close to Kariba town, which took place in 1955–59. It forms the international boundary between Zambia and Zimbabwe and was created by the colonial government for the region, prior to the independence of both countries. The lake filled between 1958­–63 and a hydroelectric plant at the dam supplies most of the electricity for both nations, while the lake is used for commercial fishing and tourism. The fringes of the lake are dotted with numerous small islands (which were large hills before the flooding of the valley) and the southern (Zimbabwean) border of the lake is occupied by Matusadonha National Park. The area is densely vegetated, with mopane forest and grassland running down to the shores, and has prolific birdlife and game. During our transfer we were entertained by white-winged terns fishing, African sea eagles flying overhead, and sightings of elephant on the shore and hippo bobbing along the the lake margins. 

Elephant and hippo were frequent visitors to our fieldsites (photo: Pia Viglietti)

The houseboat Musankwa, which was to be our home during our time on Kariba (photo: Jonah Choiniere)

The geology in the area is complex, with much faulting, and the southern shore of the lake is composed mostly of ‘Karoo-aged’ rocks thought to be equivalents to those found in South Africa, which range from Permian to Early Jurassic in age. The area has suffered some drought over the past few years, exposing more shoreline than usual, increasing the amount of land that we were able to prospect. Some of the islands are named, but many are known only by a formal numbering system. Our destination, and base for the next few days, was to be island 126/127. This was chosen as it is the type locality for the earliest known sauropod, Vulcanodon karibaensis, literally ‘the volcano tooth from Kariba’. Vulcanodon, which is known from incomplete remains, is one of the most important animals for understanding the origin of sauropods and all of the available material comes from this island. These bones are now stored in Bulawayo, but one of our aims was to find out more about this site and, hopefully, to find new material … 

The bright orange cliffs that yielded Vulcanodon on islands 126/127, capped by a dark layer of basalt (photo: Pia Viglietti)

Sunday, 5 February 2017

Lake Kariba dinosaur expedition: Part 1

Our knowledge of dinosaur evolution is based on a series of snapshots provided by the fossil record, with a handful of key regions providing the lion’s share of information for any particular time period. This relies on serendipity – rocks of the right age and type need to be preserved in a way where they are accessible for collection – and the distribution of these deposits is essentially random, due to numerous geological processes acting to different extents in different areas at different times. For example, our most detailed insights on the last dinosaurs currently come from the western USA and Canada, whereas presently our information on the earliest dinosaurs is confined to Argentina and Brazil.

Southern Africa provides an important piece in this puzzle, with a series of sandstone and mudstone deposits laid down on broad river floodplains, that were laid down at a time when dinosaurs were first starting their rise to numerical and ecological dominance. These environments became more arid through time, culminating in vast dune seas, where dinosaur fossils could still be found. This series of rocks is referred to as the Stormberg Group in South Africa and reveals not only the dinosaurs but also the other members of a series of terrestrial faunas that lived during the Late Triassic and Early Jurassic, spanning a period when several pulses of extinction rocked the world at the Triassic/Jurassic boundary. The Stormberg Group has been (and continues to be) the focus of much attention and has yielded some of the best-known African dinosaurs, which are often known from abundant and beautiful material. These include the ornithischians Heterodontosaurus and Lesothosaurus, the theropods Dracovenator and Coelophysis, and (most abundantly) the sauropodomorphs, including Antetonitrus, Massospondylus, Pulanesaura and many others.

Adjacent regions of southern Africa, including Botswana, Lesotho, Zambia and Zimbabwe, have similar sedimentary series that are thought to correlate with those in South Africa, but for various reasons these deposits are have been less thoroughly explored. Nevertheless, some important material is known from these areas, with rich localities in Lesotho (which have supplied beautiful early mammal and Lesothosaurus material, as well as dinosaur footprints) and Zimbabwe. Many sites are known in Zimbabwe, with well-known taxa such as Coelophysis and Massospondylus known from the south of the country, while the early sauropod Vulcanodon was found on the shores of Lake Kariba on its northern border. Several field crews have worked on sites in the south of Zimbabwe more recently, finding new and important material, but the potentially rich dinosaur sites around the shores of Lake Kariba have not been prospected by palaeontologsts since the time of Vulcanodon’s discovery in 1969.

More recently, a small band of dedicated amateur palaeontologists and geologists, including local safari camp owner Steve Edwards and geologist Tim Broderick, have had their eyes to the ground along the shores of Lake Kariba and have found interesting new material of their own. Steve and Tim mentioned this material to various dinosaur specialists around the world, including my colleague Jonah Choiniere (based at the Evolutionary Studies Institute in Johannesburg) and I. The presence of Vulcanodon, and other Early Jurassic dinosaurs elsewhere in Zimbabwe, as well as the exciting news that new material was being found, suggested to Jonah and I that a trip to area would be fruitful and exciting. After months of background research, building new contacts with colleagues in Zimbabwe, and raising the money, Jonah was able to organise an expedition to the Lake Kariba area, in which I was lucky enough to participate, along with several other Zimbabwean and South African colleagues. So, on the 5th January 2017 Jonah, his postdoc Pia Viglietti, our joint PhD student Kimi Chapelle and I left Johannesburg, bound for Harare …