The 250-million year rise and fall of the dinosaurs | Steve Brusatte

The Origin and Early Evolution of Dinosaurs

• The story of dinosaurs begins approximately 250 million years ago at the end of the Permian period, a time when the supercontinent Pangea existed, and the Earth experienced the worst mass extinction in its history, with about 90 or 95% of all species dying out due to enormous volcanic eruptions in what is now Siberia 10s.
• These volcanic eruptions were not like modern-day volcanoes, but rather enormous fissures in the Earth that released large amounts of carbon dioxide and methane, leading to runaway global warming and the mass extinction event 2m6s.
• Among the survivors of this extinction event were small, agile, and intelligent reptiles with long arms and legs, known as dinosauromorphs, which were no bigger than a cat and are considered the roots of the dinosaur family tree 2m6s.
• Fossil evidence of these early dinosaur ancestors, including tiny footprints and handprints, has been found in Poland and dates back to around 249-250 million years ago, providing clues about the early history of dinosaurs 2m6s.

The Emergence of True Dinosaurs and Their Classification

• The first true dinosaurs emerged about 230 million years ago during the Triassic period, characterized by changes in their pelvis and backbone that allowed them to walk upright and move quickly, and they eventually split into three major groups: theropods, sauropods, and ornithischian dinosaurs 2m6s.
• The theropod group includes meat-eating dinosaurs like T-rexes and velociraptors, as well as birds, while the sauropod group includes long-necked dinosaurs like brontosaurus and diplodocus, and the ornithischian group includes plant-eating dinosaurs like triceratops and stegosaurus 2m6s.

Challenges Faced by Early Dinosaurs

• Despite the diversity of dinosaurs that emerged during the Triassic period, they faced significant competition from other animals and were also affected by the climate and weather, making their establishment a challenging process 2m6s.
• The physical environment of Pangaea was challenging to live in, with vast deserts covering much of the supercontinent and shorelines battered by storms and mega monsoons, which were supersized monsoon systems 10s.
• The early dinosaurs had to compete with other groups that survived the extinction at the end of the Permian, including amphibians, such as salamanders the size of cars with thousands of teeth, and crocodiles with diverse diets and habits 42s.
• During the Triassic period, dinosaurs were not the dominant species, but rather second-rate characters, with crocodiles and giant salamanders being the main competitors, and it seemed like these animals would continue to thrive 1m14s.

The Triassic Mass Extinction and the Rise of Dinosaurs

• However, at the end of the Triassic period, another mass extinction occurred, caused by the breakup of the supercontinent, which led to major volcanic eruptions, global warming, and the release of carbon dioxide, resulting in the decimation of crocodiles and giant salamanders 2m6s.
• The dinosaurs, on the other hand, survived this extinction and had the opportunity to diversify in a largely empty world during the Jurassic period, but the exact reason for their survival is still unknown, with various ideas proposed, such as their ability to move faster, being more intelligent, or having feathers to insulate their bodies 3m30s.

The Jurassic Period and the Diversification of Dinosaurs

• The transition from the Triassic to the Jurassic period marked a significant turning point for the dinosaurs, as they became the dominant species and evolved into the spectacular creatures that are well-known today, which is why this period is often featured in popular culture, such as in the film Jurassic Park 4m40s.
• Dinosaurs diversified significantly during the Jurassic period, approximately 250 million years ago, due to their ability to survive a mass extinction event that eliminated many of their competitors and the breaking apart of the supercontinent Pangea, which allowed them to adapt to new environments and evolve into various species 10s.
• By the end of the Jurassic period, a wide range of dinosaur species had emerged, including famous ones like Brontosaurus, Brachiosaurus, Stegosaurus, and Allosaurus, which lived in different parts of the world, such as the American West, and their fossils can now be found in places like Colorado, Wyoming, Montana, Utah, and the Dakotas 42s.

The Cretaceous Period and the Spread of Dinosaurs

• The transition from the Jurassic to the Cretaceous period, which occurred around 103 million years ago, was not marked by a major extinction event or significant geological activity, but rather a gradual change in the continents' movement, allowing dinosaurs to continue adapting and evolving 2m6s.
• During the Cretaceous period, the fossil record becomes less abundant, but it is known that certain groups of dinosaurs, such as the Spinosaurus and Carcharodontosaurus, dominated the early Cretaceous, while others, like the Tyrannosaurs, emerged later, and this change is believed to be linked to a period of climate change and global warming 2m6s.
• The climate change and global warming event in the middle Cretaceous led to the emergence of new dinosaur species, and those that survived this period were able to thrive in the late Cretaceous, with different species inhabiting different continents, such as North America, South America, and Africa 2m6s.
• By the late Cretaceous, around 80-66 million years ago, the continents had moved to their current positions, and the dinosaur species had become distinct in each region, with the Tyrannosaurus Rex being the top predator in North America, while other species dominated in different parts of the world 2m6s.

The Diversity of Dinosaurs in the Late Cretaceous

• The top of the food chain varied across different continents during the time of the dinosaurs, with Tyrannosaur relatives dominating in Asia, Allosaurus-like dinosaurs in South America and Africa, and smaller dinosaurs and Pterodactyls in Europe, which was composed of islands 10s.
• The diversity of dinosaurs was at its peak during the latest Cretaceous period, with the most species and different species living in different places, and dinosaurs were firmly in control, despite their impending demise 2m6s.

The End of the Dinosaurs: The Asteroid Impact

• A massive asteroid, approximately six miles wide, collided with the Earth in what is now the Yucatan Peninsula of Mexico, causing massive destruction, earthquakes, tsunamis, and volcanic eruptions, and leading to a global winter that lasted for years 4m42s.
• The impact of the asteroid triggered wildfires, earthquakes, and volcanic eruptions, and the soot and debris from these events blocked out sunlight, leading to a nuclear winter that caused the collapse of ecosystems and the death of plants and animals 6m15s.
• The mass extinction event that occurred as a result of the asteroid impact led to the death of three out of every four species, with all dinosaurs, except for one type of small, feathered, and winged dinosaur, becoming extinct, and only smaller animals, such as those the size of a husky dog or smaller, being able to survive 10m45s.
• The extinction event was so severe that it wiped out all large land animals, including all non-avian dinosaurs, and had a profound impact on the Earth's ecosystems, leading to a significant reduction in biodiversity 12m10s.

The Survival of Birds and the Extinction of Other Dinosaurs

• The only dinosaurs to survive the mass extinction event were small, feathered, and winged dinosaurs, which were able to fly and were the ancestors of modern birds 14m20s.
• The only dinosaurs that survived to the present day are birds, while many other animals, including pterodactyls, reptiles living in the oceans, and ammonites, died out, but some tiny, furry, smart, and feisty creatures, which are the ancestors of mammals, were able to endure and survive due to their intelligence and endurance 10s.

The Evolution and Fossil Record of Tyrannosaurs

• The fossil record allows paleontologists to trace evolution over time, and with dinosaurs, it is possible to trace a single lineage over tens or hundreds of millions of years, as seen in the example of the Tyrannosaur family, which includes the famous T. Rex 2m6s.
• T. Rex, also known as the tyrant lizard king, was the top predator in North America at the end of the Cretaceous period, but it came from a long line of ancestors that changed, adapted, and survived over time, with the Tyrannosaur family dating back over 100 million years before T. Rex 2m6s.
• The earliest known Tyrannosaurs, such as Guanlong from China, lived around 165 to 170 million years ago and were about the size of humans, or even smaller, and were not top predators, but rather second or third-tier predators in the food chain 4m6s.
• Over time, Tyrannosaurs remained small predators until the middle Cretaceous turnover, a time of climate change that wiped out many top predators, allowing Tyrannosaurs to fill the vacant role and supersize their bodies to become the size of buses, as seen in the example of T-Rex 6m6s.

The Intelligence and Behavior of Tyrannosaurus Rex

• T-Rex was not only large, but also a very smart animal, and despite common misconceptions, often perpetuated by popular culture, such as the first Jurassic Park film, it is clear that T-Rex was a remarkable and intelligent creature 8m6s.
• The depiction of the Tyrannosaurus Rex in the first Jurassic Park film is inaccurate, as it is shown chasing a jeep at high speeds, whereas in reality, the T-Rex could probably only move at around 10 to 15 miles per hour, not fast enough to catch a jeep moving at 30 miles per hour 42s.
• The T-Rex is also portrayed as being less intelligent than it actually was, with a relatively large brain for its body size, a powerful sense of smell, keen vision, and a highly developed sense of hearing, making it a smart animal 2m6s.
• The idea that a person can avoid being detected by a T-Rex by standing still is also incorrect, as the T-Rex had a keen sense of smell and vision, and its brain was capable of processing a wide range of sensory information 2m6s.

The Physical Characteristics and Function of T-Rex Arms

• Some species of Tyrannosaurs have been found in bone beds, which are mass graveyards containing the remains of many individuals of the same species, from juveniles to adults, suggesting that they may have lived and hunted together in packs 4m30s.
• The T-Rex had incredibly powerful teeth and a large head, but its arms were relatively small, which is a puzzling feature that has been debated by paleontologists since the discovery of the T-Rex in the early 1900s 6m10s.
• The small size of the T-Rex's arms may be due to a trade-off with the increasing size of its head over the course of its evolution, as the head took on more of the functions of grabbing and processing food, making the arms less necessary 8m20s.
• Despite their small size, the T-Rex's arms were still present and may have been used for certain tasks, as evolution tends to eliminate or reduce unnecessary structures, and the fact that the arms were not completely eliminated suggests that they still had some function 10m0s.
• The evolution of whales from land-dwelling mammals is an example of how animals can adapt to their environments, and the fact that the Tyrannosaurus Rex still had arms, despite being a large animal, suggests that those arms were used for a specific purpose, such as holding onto prey or mating, and the muscular structure of the arms indicates that they were used frequently 10s.

Feathers in Dinosaurs and Their Implications

• The arms of the Tyrannosaurus Rex were relatively small compared to the size of the animal, but they were very muscular, with large scars on the bones indicating the presence of strong muscles, and the muscles that were most developed were those that would have allowed the arms to be brought closer to the body 42s.
• Many dinosaurs, including the Tyrannosaurus Rex, likely had feathers, as evidenced by fossil discoveries such as those of the D-Long and Eutyranus, which were found to have feathers or quill knobs, and this challenges the traditional depiction of dinosaurs as scaly, reptilian creatures 2m6s.
• The discovery of feathers on dinosaurs has been met with some resistance, but it is supported by fossil evidence, and it is likely that many dinosaurs, including the Tyrannosaurus Rex, had feathers, which would have made them appear more bird-like than reptilian 2m6s.

The Discovery and Diversity of New Dinosaur Species

• New dinosaur species are being discovered at a rapid pace, with about 50 new species found every year, and it is estimated that there may have been millions of dinosaur species that once existed, but only a small fraction of these have been discovered so far 4m6s.
• The study of dinosaurs and other prehistoric animals, such as mammals, can provide valuable insights into the evolution of life on Earth, and the discovery of new species and fossils continues to expand our knowledge of the natural world 6m6s.

The Rise of Mammals and Their Coexistence with Dinosaurs

• Mammals and dinosaurs have a shared history, and understanding mammal evolution is essential to understanding our own origin story, with the asteroid that ended the age of dinosaurs also marking the beginning of the age of mammals, which has lasted for the last 66 million years 10s.
• The characteristics that define mammals include having hair, different types of teeth such as molar, premolar, incisors, and canines, feeding babies milk, having big brains, a keen sense of smell, a very good sense of hearing, a single lower jawbone, and strong jaw muscles 42s.
• There are three major types of mammals: placental mammals, which make up about 95% of all mammals and can give live birth to well-developed babies, monotremes, which are primitive mammals that lay eggs, and marsupials, which give birth to tiny babies that develop further in their mother's pouch 2m6s.
• The roots of these three major groups of mammals can be seen in the fossil record, dating back to the Cretaceous period, and the characteristics that define mammals did not evolve all at once, but rather one by one over time in many ancestors 2m6s.
• The first true mammals appeared around the late Triassic period and early Jurassic period, around the same time as the first true dinosaurs, with features such as hair evolving even earlier, in the Permian and early Triassic periods 2m6s.
• Dinosaurs and mammals coexisted for a long time, starting from the Triassic period, but they had different fates, with dinosaurs becoming massive and mammals becoming small, with no mammal bigger than a house cat, and their brains getting bigger, jaws simplifying, and teeth changing as they got smaller 10s.

Adaptations and Survival Strategies of Early Mammals

• As mammals miniaturized their bodies, they developed adaptations such as drinking milk, having one set of baby teeth and one set of adult teeth, and some bones in their lower jaw moving into the ear to amplify hearing, which are characteristic of mammals 42s.
• The stereotype that mammals living with dinosaurs were small and boring is not accurate, and fossils found in northeastern China have revealed a great diversity of small mammals, including those that could burrow, climb, run, swim, and glide, which lived in the understory and underground, avoiding dinosaurs 2m6s.
• Mammals and dinosaurs reached an equilibrium, keeping each other in check for 150 million years, with dinosaurs keeping mammals small and mammals keeping dinosaurs big, as evidenced by the lack of small dinosaur fossils and the presence of small mammal fossils 4m6s.

The Cretaceous Terrestrial Revolution and Flowering Plants

• During the Cretaceous period, there was a burst of evolution known as the Cretaceous terrestrial revolution, which was triggered by the rise of flowers and had a significant impact on life, food webs, and ecosystems, with flowers becoming a dominant feature of the environment 6m6s.
• The Cretaceous terrestrial revolution was a significant event that touched many aspects of life, and it was characterized by the diversification of mammals and other species, and the rise of flowering plants, which are now a ubiquitous feature of the environment and a key part of the food chain 8m6s.
• The majority of plants today are flowering plants, but they are a relatively new innovation in the history of life, with the oldest fossils of plants with flowers dating back to the Cretaceous period, and their diversification triggered the diversification of insects and other animals that interacted with them 10s.
• As flowering plants diversified and adapted, some became trees, such as palm and magnolia trees, and this led to the evolution of insects that pollinated these flowers, as well as animals that ate these insects, leaves, flowers, fruits, and roots, including mammals that blossomed during the Cretaceous-Terrestrial revolution 42s.
• During this revolution, mammals evolved new types of teeth, including molar teeth that could both shear and crush food, which are very distinctive and intricate, and allowed mammals to take advantage of new food sources such as insects, flowers, and fruits 2m6s.

Mammals in a Dinosaur-Dominated World

• Mammals had to survive and endure in a dinosaur-dominated world, where a single footstep of a large dinosaur could obliterate a whole colony of mammals, and they had to learn to live incognito, but this also set them up to take advantage of the asteroid impact that eventually led to the demise of the dinosaurs 2m6s.
• When the asteroid hit, the dinosaurs were vulnerable and succumbed, but mammals had fine-tuned their survival abilities and were able to stare down the asteroid, and during the first 10 million years after the asteroid impact, there were many new mammals that evolved, including placental mammals that could give birth to larger babies 4m6s.

New Research on Mammal Evolution

• Research led by Ornela Bertrand, a postdoc scholar, has recently uncovered a new story about the evolution of mammals, which challenges some of the existing ideas about what we think of when we think of mammals, and this research has been conducted at the University of Edinburgh 6m6s.
• Early mammals that lived with dinosaurs evolved relatively large brains for their body size, which may have helped them survive the asteroid impact that led to the demise of the dinosaurs 10s.
• After the asteroid impact, mammal brains actually decreased in size relative to their bodies during the first 10 million years, with their bodies getting significantly larger as they filled the niches left by the extinct dinosaurs 42s.

The Post-Astroid Expansion of Mammals

• The rapid growth in body size of mammals after the asteroid impact is evident in fossil records, such as those found in New Mexico, where mammals the size of pigs and cows appeared within 200,000 years and 1 million years, respectively, after the asteroid impact 2m6s.
• The driving force behind the evolution of mammals during this period was not intelligence, but rather the need to get bigger and fill the available ecological niches, with intelligence catching up later, around 10 million years after the asteroid impact 2m6s.
• The early mammals that dominated the landscape during the first 10 million years after the asteroid impact were archaic placental mammals, such as Pantodonts, Taeniodonts, Tillodonts, and Condylarths, which eventually went extinct but gave rise to the ancestors of modern mammal groups, including primates 2m6s.

The Emergence of Modern Mammals

• The emergence of modern mammals, including primates, occurred around 55-56 million years ago, during the transition from the Paleocene to the Eocene interval, a period marked by significant global warming caused by volcanic activity 2m6s.
• The eruption of volcanoes in Iceland, which started over 250 million years ago, released large amounts of lava, causing global warming, but did not lead to a mass extinction, and instead triggered a mass migration of mammals 10s.
• As the North Atlantic Ocean opened up, the lava flows scorched parts of Scotland, including field sites with Jurassic-age dinosaur bones, and this period of upheaval and change allowed modern primates, rodents, and hoofed mammals to become dominant 10s.

Mammal Migration and Dispersal

• The high latitudes were free of ice during this time, making it easy for mammals to move around and settle in new areas, leading to the emergence of new species, such as bats and whales, and the extinction of more archaic mammals 10s.
• Mammals have been able to move and adapt to their environments throughout Earth's history, but the separation of continents has made it more difficult for them to migrate, except for those that can fly, such as bats, which evolved around 55 or 56 million years ago 10s.
• Some mammals have been able to migrate across continents through "Hail Mary dispersals", where they are able to travel long distances by chance, such as the migration of primates and rodents from Africa to South America, which was made possible by their close genetic relationship to African species 2m6s.

The Evolution of Mammal Dispersal Mechanisms

• The genetics of South American mammals, such as howler monkeys and guinea pigs, show that they are closely related to African rodents and primates, indicating that they must have migrated from Africa to South America at some point in the past 2m6s.
• The rise of mammals occurred through Hail Mary dispersals, where mammals such as rodents and primates traveled to distant lands on rafts of vegetation after storms, and this process was made possible by the large amount of time evolution had to work with 10s.

The Transition to the Age of Mammals

• After the asteroid hit, the Cretaceous period turned into the Paleocene, marking the end of the age of dinosaurs and the beginning of the age of mammals, and during this time, the Earth was still very warm with no ice caps at the poles 2m6s.
• The Earth got even warmer as the Paleocene turned into the Eocene, with a spurt of global warming that allowed crocodiles to lounge in the shade of palm trees above the Arctic Circle, but it started to gradually get cooler about 35 million years ago 2m6s.
• The cooling trend was driven by changes in the orbit of the Earth and the amount of carbon dioxide in the atmosphere, as well as the isolation of Antarctica, which allowed cold water currents to encircle it and acted as a global air conditioner 2m6s.
• The isolation of Antarctica led to the growth of glaciers into ice sheets, which helped drive the temperature of the entire world to be much cooler, and this long-term trend continued for many tens of millions of years 2m6s.

The Ice Age and Its Impact on Mammals

• About two and a half million years ago, another interval of change occurred, with changes in the orbit of the Earth and the shape of its axis converging to make the Earth receive less light and energy from the sun, plunging it into a proper ice age 2m6s.
• The current ice age, which started about two and a half million years ago, is still ongoing, but the Earth is being heated quickly through global warming, and over the last two and a half million years, the Earth has been cold, but not entirely covered in glaciers 2m6s.
• The polar ice sheets have grown and contracted in many pulses over time, with one of the peaks of expansion occurring about 50,000 years ago, covering areas such as Chicago, Edinburgh, and New York City in a mile-thick layer of ice 10s.

Comparing the Sizes of Dinosaurs and Mammals

• During this time, various mammals lived on the fringes of the ice sheets, including woolly mammoths, Saber-toothed tigers, woolly rhinoceroses, armadillos the size of Volkswagen's, and giant deer with large antlers, which adapted to the cold environment by growing big and developing shaggy coats of hair 42s.
• In comparison to these mammals, some dinosaurs, such as Argentinosaurus and Patagotitan, were enormous, weighing 50-60 tons or more, and pushed the boundaries of what is biologically possible, with no mammals able to reach such sizes 2m6s.

The Respiratory System of Dinosaurs and Birds

• The reason for this size difference may be attributed to the unique breathing system of dinosaurs, which is similar to that of birds, featuring a unidirectional airflow and air sacs that allow for more efficient oxygen intake, unlike the bag-like lungs of mammals 2m6s.
• This efficient lung system, also found in birds, enables them to fly at high altitudes, such as over the Himalayas, without needing oxygen masks, whereas mammals would require supplemental oxygen at such heights 2m6s.
• The presence of this bird-like lung system in dinosaurs is inferred from the characteristic invasion of air sacs into the bones, creating holes and chambers, which is evident in fossils of dinosaurs like T-rex and long-necked dinosaurs 2m6s.
• The structures found in birds today are also present in T-Rex and long-neck dinosaurs, and these dinosaurs had ultra-efficient lungs that allowed them to take in more oxygen than mammals, which is likely a reason why they were able to grow larger than the biggest land-living mammals, such as elephants and rhinos 10s.

The Evolution of Whales from Land Mammals

• Whales are mammals that have adapted to living in the ocean, with characteristics such as hair, whiskers, and eyelashes, and they feed their babies milk, and DNA testing has confirmed that they are closely related to hippos, with whom they share a common ancestor 1m5s.
• The evolutionary transformation of whales from land mammals to ocean mammals can be traced through fossil records, which show a sequence of transitional stages, starting around 55 million years ago with small hoofed mammals that lived on land but had dense bones that allowed them to spend time in the water 2m6s.
• The fossils of these early whale ancestors show how their hooves changed into flippers, and their bodies became more streamlined, eventually becoming fully ocean-living species that could no longer survive on land 2m6s.

The Possibility of Cloning Extinct Species

• It is highly unlikely that dinosaurs could be brought back to life through cloning, as DNA breaks down quickly after an animal dies, and no DNA older than about 1.5 million years has been found, but it may be possible to clone more recently extinct species like woolly mammoths and saber-toothed tigers, for which complete genomes are available 6m30s.
• The complete genome of the woolly mammoth is known, and more is understood about its DNA than about many living animals, which could potentially make it a candidate for cloning or other forms of genetic restoration 7m20s.
• The possibility of bringing back extinct species, such as the woolly mammoth, is considered, but it poses ethical risks as the world today is vastly different from the one they knew, with their habitats having mostly disappeared 10s.
• The extinction of woolly mammoths and other megafauna is attributed to human activities, including overhunting, changing the environment, and clearing land, rather than natural disasters like asteroids or volcanoes 42s.
• The idea of bringing back extinct species raises questions about rectifying past mistakes and making amends for the harm caused by human actions, making it a complex and multifaceted ethical debate 1m6s.

Birds as Living Dinosaurs

• Birds are classified as true dinosaurs, having evolved from other dinosaurs, and are the only dinosaurs to have survived to the present day, with their ability to fly being a unique adaptation 2m6s.
• The evolution of birds from dinosaurs is a fascinating topic, with birds developing feathers, wings, and the ability to fly, and has inspired further study and appreciation for these creatures 2m30s.
• Extinct birds, such as terrorbirds, were extreme and eccentric, with some species becoming top predators in their ecosystems and growing to be larger than humans, highlighting the diversity and complexity of bird evolution 3m30s.
• The prehistoric world was inhabited by massive birds, including the "demon ducks" that lived in Australia for tens of millions of years, which were big, plant-eating birds that were around a hundred times the size of a modern duck 10s.

The Diversity and Evolution of Prehistoric Birds

• These "demon ducks" were important plant-eaters at the base of the food chain in Australia, along with marsupials like kangaroos and wallabies, and were likely driven to extinction by early human ancestors who ate their eggs 42s.
• Other massive birds included the "elephant birds" from Madagascar, which stood around ten feet tall, weighed over 700 pounds, and laid eggs the size of watermelons, as well as the "colossus penguins" that were taller than humans and weighed as much as gorillas 1m30s.
• Many of these large birds, such as the penguins, demon ducks, and elephant birds, were flightless, having given up the ability to fly in order to grow to such large sizes, but there were also birds like the Pelagornithids that maintained the ability to fly despite their large size 2m6s.

The Evolutionary Link Between Birds and Dinosaurs

• The Pelagornithids were characterized by their 20-foot wing spans, allowing them to soar through the air like giant kites or hanggliders, and were able to fly for many tens of millions of years 2m40s.
• The idea that birds evolved from dinosaurs is not a new concept, but rather one that dates back to the time of Charles Darwin, with his friend Thomas Henry Huxley proposing this idea in a series of lectures in the 1860s as a way to communicate the concept of evolution to the public 4m10s.
• Huxley's proposal was based on the understanding that modern birds possess many distinctive characteristics, such as feathers, wings, and lightweight skeletons, which are shared with their dinosaur ancestors, and was an important step in popularizing the concept of evolution 5m0s.
• The discovery of fossils with bird-like features, such as the foot of a chicken resembling the foot of a small meat-eating dinosaur, led to the realization that birds evolved from dinosaurs, with this understanding emerging in the 1860s 10s.
• The discovery of the Archaeopteryx fossil in southern Germany, which dated back to the Jurassic period around 150 million years ago, provided significant evidence of the link between birds and dinosaurs, as it had characteristics of both, including wings, feathers, teeth, and a long bony tail 42s.
• By the end of the 1860s, the idea that birds came from dinosaurs had gained widespread acceptance, with even Darwin incorporating it into his later editions of "The Origin of Species", although it later faced challenges from the discovery of larger, less bird-like dinosaurs 2m6s.
• The debate over the origin of birds continued for many decades, until the discovery of bird-like raptor dinosaurs, such as Velociraptor and Dinonychus, and the finding of feathers on dinosaur fossils in the 1990s, ultimately confirmed that birds did indeed evolve from dinosaurs 2m6s.

The Survival and Diversification of Birds

• Today, there are over 10,000 species of birds, all of which descended from a single common dinosaur ancestor that evolved the ability to fly, with this ancestor and its descendants having to survive numerous challenges, including the asteroid that ended the Cretaceous period and wiped out 75% of all species 2m6s.
• The ability of birds to fly, their small size, and other characteristics may have helped them survive the mass extinction event that killed off the other dinosaurs, allowing them to eventually give rise to the diverse range of bird species that exist today 2m6s.
• The mass extinction event that occurred when the asteroid hit the Earth led to the survival of only one type of bird, which is the modern bird, and it is believed that their ability to fly, grow quickly, and reproduce fast, as well as their possession of beaks that could eat seeds, helped them survive in a environment with limited food sources 10s.
• The ability of modern birds to eat seeds was crucial for their survival because seeds can last a long time and can be found even after disasters such as forest fires or volcanic eruptions, allowing them to have a steady food source when other animals were struggling to find food 42s.
• The characteristics that enabled birds to survive, such as their beaks, small size, and ability to fly, are thought to have been the key factors that allowed them to thrive in a challenging environment, and birds like Asteriornis, which is known from Europe and Antarctica, are examples of modern-style birds that were able to survive and adapt to the new environment 2m6s.

The Anatomy and Evolution of Birds

• Birds are unique and distinctive animals, with characteristics such as feathers, light skeletons, and wishbones that act as springs, which all work together to enable them to fly, and it is believed that these features evolved gradually over time in the dinosaur ancestors of birds, long before they could fly 4m6s.
• The evolution of birds is a story of gradual and piecemeal evolution, with different features evolving over tens of millions of years in different dinosaur ancestors for different reasons, and eventually coming together to form a flying machine, similar to how the Wright brothers invented the airplane by combining existing components 6m6s.
• The fossil record shows that the classic features of birds, such as feathers and wishbones, first evolved in the dinosaur ancestors of birds, and it is thought that these features evolved for reasons other than flying, but eventually came together to enable birds to fly 8m6s.

The Evolution of Bipedalism in Dinosaurs

• The concept of walking bipedally, or on hind legs, is a unique feature in nature, with humans and birds being the primary examples, and this trait first evolved in early dinosaurs during the Triassic period, probably to move faster and free their hands for other tasks 10s.
• The evolution of bipedalism in dinosaurs had nothing to do with flying, but rather was an adaptation for efficient movement and freeing the hands for other activities such as grabbing food 2m6s.

The Evolution of Feathers in Dinosaurs

• Feathers are a distinctive feature of birds, but the fossil record shows that many dinosaurs also had feathers, with dozens of types of dinosaurs found with feathers all over their bodies, including small and large dinosaurs, plant-eating and meat-eating dinosaurs 4m5s.
• The presence of feathers in many dinosaur species suggests that feathers evolved deep in dinosaur history, possibly in the common ancestor of all dinosaurs, and were a normal feature of dinosaurs, similar to how hair is normal for mammals 5m30s.
• Most dinosaurs had simple feathers that were similar to hair, hollow, and made of beta proteins, which were likely used for controlling body temperature and staying warm, rather than for flying 6m40s.
• Some dinosaurs, such as the raptor dinosaurs, evolved more complex feathers that were densely packed, branched, and rigid, and were used to form wings on their arms, legs, and tails, which eventually became the classic quill pen feathers of birds 8m20s.

The Evolution of Wings and Flight

• The evolution of wings in dinosaurs is a complex process, and fossils have shown that wings first appeared on dinosaurs the size of sheep to horses, with wings no larger than a laptop screen, which would not have been sufficient to generate lift and thrust for flight 10s.
• The initial purpose of wings is believed to have been for display, such as attracting mates or intimidating rivals, with elaborate colors and patterns on the wings, similar to a peacock's tail, and only later were they repurposed as airfoils for flying 42s.
• The exact process of how wings were repurposed for flying is not clear, and it is possible that this happened multiple times in different dinosaur lineages, with modern birds being just one of the successful experiments in flying 2m6s.
• There is evidence of multiple experiments in flying, with different types of dinosaurs having distinct wing configurations, such as wings on their arms, legs, or tail, and some having wings made of skin, like the dinosaur Yi qi from China 2m6s.
• The variety of wing configurations suggests that different dinosaurs were trying out different ways of flying, and it is likely that modern birds evolved from a group of small, feathered dinosaurs that were able to experiment with different flying styles 2m6s.

Theories on the Origin of Flight in Birds

• One theory of how modern birds learned to fly is the "ground up" theory, which proposes that small dinosaurs used their wings to generate lift and thrust while running, allowing them to defy gravity, but this is just one of several theories and the true process remains unclear 4m6s.
• The evolution of dinosaurs to fly is explained by two main theories: one suggesting that it happened from the ground up, and the other from the trees down, with small dinosaurs using wings to display, glide, and parachute, and then gaining control by flapping their wings 10s.
• Evolution through natural selection does not work with a plan in mind, but rather fits individuals and their populations to their own time and place, leading to the accumulation of features over time, such as the development of wings in dinosaurs, which eventually led to the evolution of birds 2m6s.

The Transformation of Dinosaurs into Birds

• After some dinosaurs started to fly, evolution continued to turn their bodies into more efficient flying machines, with changes including the shortening of their tails and the development of beaks, replacing the long, straight, bony tails and razor-sharp teeth of their ancestors 2m6s.
• The tails of birds today are reduced to a small nubbin of bone, called the pygostyle, which anchors a bunch of feathers used for steering, braking, and as a rudder, especially during takeoff and landing 4m6s.
• The development of beaks in birds is believed to have happened independently multiple times, possibly due to dietary changes, such as eating insects, seeds, or other foods that were more accessible through flight, rather than solely due to the need to reduce weight for flying 6m6s.
• By the end of the Cretaceous period, a diverse range of birds had evolved, including some with primitive characteristics, such as teeth and long tails, and others that resembled modern birds, with beaks, short tails, and fan-like tail feathers 8m6s.

The Soundscape of the Cretaceous World

• The soundscape of nature is dominated by birds, with their singing, tweeting, and squawking, and they have a unique ability to learn and mimic sounds, similar to how humans learn language, with a babbling phase like that of a toddler 10s.
• The evolution of this ability is an interesting question, as it raises the possibility of what the soundscape of the Cretaceous world, inhabited by dinosaurs like the T-Rex, would have been like, and whether it would have been similar to the modern world or very different 1m15s.
• The movies often portray dinosaurs as roaring like lions, but this is not accurate, as the unique vocal cords and bones of the throat of big cats enable them to produce this sound, and it is not a characteristic of dinosaurs 2m6s.
• Sound does not fossilize, so there is no direct evidence of what the Cretaceous world sounded like, but sometimes clues can be found in the fossils themselves, such as the preservation of vocal organs 2m45s.
• The discovery of a bird fossil, Vegavis iaai, from around 68-69 million years ago in Antarctica, provides a clue, as it had a syrinx, a uniquely bird-like voice box, which is capable of producing a wide range of sounds and is found in modern birds 3m30s.
• The syrinx is a remarkable organ, with some of the fastest twitching muscle in the animal kingdom, and allows birds to produce complex sounds, including speaking-like abilities in some species 4m15s.
• The presence of the syrinx in some Cretaceous birds suggests that they may have been able to produce sounds similar to those of modern birds, but more research is needed to fully understand the evolution of bird vocalization 5m0s.

The Intelligence and Behavior of Birds

• Birds are incredibly diverse, with some species migrating long distances, others evolving new species, and some, like crows, ravens, and parrots, possessing large brains and advanced intelligence, allowing them to use tools and mimic human speech 6m0s.
• The intelligence of birds, particularly species like crows and parrots, is often underestimated, and their ability to fashion their own tools and recognize themselves in mirrors is a remarkable feat, similar to that of humans and some primates 7m0s.

Birds as Living Dinosaurs and Their Scientific Significance

• The study of birds has inspired a lot of research on the evolution of cognition and intelligence over time, and a team of scientists, including zoologists and neurobiologists, are working together to make links between the intelligence and behaviors of modern species, especially birds, and dinosaurs like T-Rexes and Brontosaurus 10s.
• Birds are considered to be real, living dinosaurs, as they evolved from dinosaurs, are part of the dinosaur family tree, and have all the classic features of dinosaurs, making them the only dinosaur that has survived various catastrophes and extinctions to reach the present day 1m30s.
• The fact that birds are living dinosaurs provides an opportunity to watch, experience, and appreciate actual, real dinosaurs, and they are the only members of the dinosaur family that have made it to the world today, giving scientists a chance to study and learn from them 2m6s.
• The research on birds and dinosaurs is being conducted by a team at the University of Edinburgh, led by a scientist who has come to love and appreciate birds, and has been inspired by them to study the evolution of cognition and intelligence, and to try to understand how dinosaurs sensed their world 42s.