This episode of the award winning science program NOVA is about Birds and how they are modern dinosaurs. it examines their evolution, deep past and how they got where they are at today.
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#NOVA #PBS #documentaries #Science #dinosaurs #birds #evolution #paleontology
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00:00birds live across our entire planet around 50 billion of them fill our skies seas and
00:16landscapes each of the 11,000 species expertly adapted for the environments they inhabit but
00:24how do they come to be such an evolutionary triumph the answer lies with their ancestors today's birds
00:33are dinosaurs they are every bit as much of a dinosaur as a t-rex's or brontosaurus but
00:41exactly how this spectacular evolution took place is still somewhat a mystery right now we have very
00:49little data I mean that's how it is with paleontology you have hundreds of millions of
00:53years and just a few fossils scattered around the world now a new breed of scientist is making
01:00spectacular discoveries we scanned it and then what we found was a lot of skeleton underneath
01:08the rock holy cow to fill in the gaps of this evolutionary tale we thought it's just going
01:16to be a simple thing they like dinosaurs or they like birds and what we found is that they are
01:21like neither and answer one of paleontology's biggest questions why were birds the only
01:28dinosaurs to survive the asteroid impact 66 million years ago the development of new technologies has
01:36provided us with a richer picture of avian evolution than has ever previously been possible dino birds
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02:19birds are full of surprises they lay eggs like reptiles but have warm blood like mammals only birds
02:38have feathers and it's one of their most distinctive characteristics there are 11 000 species across
02:45the globe dazzling in their variety size shape and behavior we think we know them well but beneath those
02:54colorful feathers lurks an enduring mystery why are birds here scientists have discovered that they are the
03:04the sole surviving branch of the dinosaurs when an asteroid wiped out nearly all animal life 66 million
03:13years ago birds somehow survived while all other dinosaurs disappeared why was it pure chance or did
03:21they possess some special advantage that set them apart now new discoveries in paleontology and evolutionary
03:30biology might finally be providing answers
03:45i think this is going to be a great place to see some birds oh i agree historically it's fossils that have revealed the past to us
03:52but in the case of birds the record is patchy their fossil remains are notoriously rare and fragile
04:01hey over there eurasian griffin vulture
04:06so you've got two griffin vultures on top and then one below oh i can see yeah don i think they're warming
04:12up before they take off do you see it stretching its wings i think so yeah i think that vulture is about ready
04:19to go oh wow that is a huge bird oh my goodness
04:34this is such an amazing place to come bird watching but these birds are never going to turn into fossils
04:39right it's not the sort of environment that is conducive to fossil formation
04:43the bird fossil record is particularly sparse and that's because birds are by their very nature fragile animals
04:55and the very lightweight nature of bird skeletons which tend to be filled with air to make them even
05:01lighter as a specialization for flight and those are features that tend to conspire against their
05:07preservational potential in the fossil record this left the story of bird evolution virtually unwritten
05:16for decades barely a clue to tell us where today's four main groups of birds all came from but every now
05:23and then fossils do appear and when that happens a new chapter of the story is unlocked
05:30one of the greatest of these fossil finds lies in the heart of london in the treasure room of the natural
05:41history museum
05:45this is archaeopteryx one of the most amazing fossils in the world
05:51found just two years after charles darwin published his ideas of natural selection
05:57archaeopteryx was one of the many great 19th century dinosaur discoveries
06:03dinosaurs took over the earth some 220 million years ago evolving from reptilian relatives
06:11they inherited from reptiles the defining features we associate with dinosaurs today
06:17big claws sharp teeth but with one major difference
06:21dinosaurs whether they walk on four legs or two have an upright stance their legs below their bodies
06:29in reptiles however the legs extend horizontally from their bodies over the 140 million years that
06:37dinosaurs ruled the earth countless species came and went the approximately 150 million year old dino
06:45bird archaeopteryx has turned out to be one of the most important in the story of bird evolution
06:52with the discovery of archaeopteryx and some of the first dinosaurs even then the earliest paleontologists
06:58looked at these things and are like birds are dinosaurs i mean the skeletal similarity is enormous
07:03archaeopteryx provides us with an amazing glimpse at a combination of features that we expect to see in
07:09living birds in the present day like large feathered wings as well as the kinds of features that we
07:15associate with dinosaurs like a long bony tail jaws full of sharp pointy teeth and strong claws it bore an
07:25uncanny resemblance to a known dinosaur fossil
07:38hello there good morning olivia good to see you should go look at some fossils yeah sure okay let's take a look
07:43this is the skeleton of compsignathus which was a really important theropod dinosaur in the 19th century
07:53because it helped convince thomas henry huxley that there might be an evolutionary link between birds
08:00like archaeopteryx and theropod dinosaurs
08:07compsignathus and archaeopteryx have some surprising similarities
08:12they both would have walked on two legs had long arms long bony tails and teeth
08:21features that convinced huxley that birds were likely descended from dinosaurs
08:26a controversial theory in the 19th century this idea was rejected for a hundred years
08:32primarily because dinosaurs did not preserve or no known dinosaur at the time had a fossilized
08:38furcula that's the wishbone but then you know in the 70s the first dinosaur wishbone was found
08:44the discovery of dinosaurs with wishbones a feature previously only found in birds sealed the deal
08:51and we now recognize without the doubt that confirmators archeropteryx and modern birds
08:57all belong to theropod dinosaur the group of three toad meat eating dinosaur like t-rex
09:04despite this evolutionary link there are still mysteries creatures with early feathers that don't look
09:12like modern birds and archaic birds ancient species whose evolutionary lines are now extinct that have
09:19bird-like beaks but filled with teeth but when was the moment one evolved into the other when modern birds
09:27first appeared how did dinosaurs take flight and why did some birds survive when all other dinosaurs died out
09:38today new discoveries are revealing important new clues
09:43it's an amazing time to be studying bird evolution
09:47on the border of the netherlands and belgium quarry excavations have revealed the world
09:52as it was 67 million years ago not long before an asteroid killed off 75 of animal species on earth
10:02welcome to the very last days of the dinosaur era this is it so what we see here was basically what
10:09was deposited in a shallow sea quite warm during the last days of the era of dinosaurs
10:15we can really compare this with the caribbean or the indonesian archipelago these days sounds good
10:23it's a good place for vacation these shallow seas provide the perfect conditions for fossilization
10:29to occur a wet environment where sand and mud cover remains quickly waters filled with hungry mosasaurs
10:37whose fossils would come to light millions of years later
10:40so this begins somewhere in the range of about 67 million years seven and a half something like
10:47that and then going up these layers of rock protected one of the most incredible bird fossils ever found
10:54a chance discovery made by an amateur fossil hunter in the year 2000 this is the level that produced both
11:01bird fossils right i think it's time to unwrap the birds all right and here it is
11:08this is the only known specimen of asterionis maastrichtensis i still remember what my first
11:17impression of this fossil was like when i looked at it and it wasn't a very positive impression it
11:24wasn't until 18 years after its discovery that daniel field began studying the specimen this fossil
11:32clearly preserves a few bird bones and those bird bones are not well preserved you can see there's a broken
11:38thigh bone on top and there's a broken shin bone underneath but these are clearly the bones of
11:44birds and so even though the fossil didn't look very beautiful at first we thought maybe it would tell
11:50us something about what birds were like just before the asteroid wiped out the giant bird cousins the large
11:57dinosaurs using a ct scanner daniel and his team were able to digitally remove the rock and reveal what
12:05secrets it held within what he saw exceeded his wildest dreams
12:20when we removed the low density rock and saw the skull staring back at us my phd student won and i could
12:27not believe our eyes it was a shock it was really exciting and we realized immediately that this fossil
12:35was going to be very important because it could provide us with information that no other fossil ever
12:41discovered could it was very exciting and one of the most exciting moments of my scientific career
12:48this specimen provides a portrait of a bird that lived 66.7 million years ago
12:55this fossil is extraordinary because it shows several features that tell us that it is a member of the
13:02modern bird group and the most obvious of those features is the fact that it does not have any teeth
13:09the remains of ancient archaic birds have beaks filled with teeth losing them was a key stage in
13:16the evolution of dinosaurs into modern birds and the fact that this fossil has a beak very similar
13:23similar to living generalist birds suggests that it probably would have been happy eating almost
13:29anything it could find just like birds with similar beak shapes do today in addition to that if you look
13:36at the leg bones of this fossil they're relatively narrow and relatively long and those are features that
13:44we associate with predominantly living on the ground in the present day around seven or eight inches tall
13:52with the beak of a chicken in the head of a duck this creature is one of the oldest modern birds ever to be unearthed
13:59scientists named the 67 million year old species asterionis after asteria the greek titan goddess of falling stars
14:09it confirms that modern birds existed alongside the dinosaurs before their extinction
14:15this small bird bears witness to a world proud by t-rex and triceratops
14:21neither the largest nor the most dominant
14:24its omnivorous feeding habits mean that it's satisfied with small shellfish and seeds
14:30it might also scavenge leftovers perhaps even a washed up mosasaur carcass
14:40with its toothless beak and variety of food options asterionis is well equipped to survive in the realm of the
14:45dinosaurs but with such of all features it's unlikely that it was the first modern bird
14:53of rockefeller university in new york eric jarvis and his team are taking a different tactic to find
15:02the beginning of today's birds using modern dna to map their evolutionary past the way we dated the
15:10origin of modern birds is we took the genome scale tree which is alignment of dna from one species to
15:16another this reveals the genetic code for certain traits in modern birds that they can then look
15:22for in ancient fossils then we took fossil data that's been collected from all around the world
15:29and placed those fossil dates on the tree for like 20 species this tree allows eric to see exactly where
15:37different species of living birds genetically diverged but what the team really wants to find out
15:43is when these divergences took place what does dna suggest about when modern birds first appeared
15:51you look at mutations that occurred over time and from those mutations you can get what's called the
15:57molecular clock how much time do you need to have one mutations two three four five by estimating this
16:04rate of mutation eric wound back the clock and put a time stamp on when certain characteristics changed
16:10so from the combination of this molecular clock the tree structure and the fossil evidence all three
16:16of those combined we can date when modern birds originally formed and that was 90 million years ago
16:23fossils confirm that modern birds and their giant dinosaur cousins coexisted and dna indicates this
16:30wasn't a short-term arrangement they lived alongside one another for some 25 million years perhaps even
16:37longer and new research is showing just how similar the lives of ancient birds would have been to birds
16:44today this is the most complete and best preserved over raptor embryo skeleton in history this is the egg of a
16:53type of dinosaur that lived in asia 70 million years ago they were arranged in a circle
16:59for some reason perhaps because flood water covered the entire nest in sand they died quietly in this way
17:08and it looks like it was fossilized right before it would have hatched so in looking at this fossil
17:14we are glimpsing the last moments of a dinosaur's development in the egg before it would greet the world
17:22what we're seeing with this fossil is that these dinosaurs would have developed in their eggs and
17:28hatched from their eggs just like birds do today it's the remains of embryonic dinosaurs and their
17:39shells that have helped scientists answer one of the great questions surrounding bird evolution of all
17:47animals alive today there are only two groups of animals that are warm-blooded mammals and birds it's a
17:53key feature of what makes flight possible you have more energy available that allows you to be more
18:00active which allows you to move greater distances dinosaurs were first assumed to have cold blood
18:08and so we are very interested in knowing when this warm-bloodedness evolved in birds
18:13scientists scientists have been investigating the question for decades and recently key evidence
18:24came from dinosaur eggshells that eggshell formed within the body of the mother dinosaur geochemist
18:32robin dawson analyzed minerals in the fossilized shells to reveal what temperature they formed at
18:38in other words the mother's body temperature we looked at eggshell from the major clades of dinosaurs
18:46major groups have body temperatures that are warmer than their environment which suggests to us that
18:51they actually have the capability to have a high metabolism raise their body temperature above their
18:57environment like their warm-blooded relatives like living birds for sure dinosaurs were warm-blooded but
19:04actually some dinosaurs like stegosaurs and duck-billed dinosaurs actually secondarily evolved to be
19:10cold-blooded which i think why we were having difficulty deciding if dinosaurs were warm-blooded or
19:15not because you know there was a conflicting signal with warm blood dinosaurs would have a lot of energy to expend
19:23raising interesting questions like would they have had enough energy for a high intensity activity like flight
19:30it's the most physically demanding form of vertebrate locomotion so you have to be warm-blooded
19:37but even if their metabolism supported flight what about the equipment like wings and feathers
19:44for 20 years this was the only snag in the dinosaur bird evolution theory where did feathers come from
19:51in niaoning china the subsoil of the chow young bird fossil national geopark reveals a dinosaur world that
20:02existed between 112 and 132 million years ago buried under volcanic ash the fossils are spectacularly preserved
20:13the most famous are housed in a vast building a long winding walkway hangs above the geological
20:21layers and the fossils they contain
20:26we've discovered many micro raptors here as well as birds like compusius ormus but it's not just the
20:31sheer number of fossils found here it's what they've revealed to the world
20:35you can see that the micro raptor found here has feathers feathers a discovery that has revolutionized
20:47the world of paleontology because a micro raptor is not a dino bird but still a dinosaur a non-avian
20:54theropod in the 90s with the discovery of feathered dinosaurs i mean it was one of the most compelling
21:01arguments for the birds are dinosaurs hypothesis the discoveries kept coming and now there are
21:06thousands of feathered dinosaur fossils that are known and it wasn't only small ones
21:12more than 100 years after a link was first made birds were finally confirmed as part of the dinosaur
21:18lineage and scientists were one step closer to understanding the origins of flight but if anything
21:26this discovery raised as many questions as it answered why did dinosaurs develop feathers in the
21:32first place what advantage did they provide paleontologist zhu jing from the institute of vertebrates in
21:45paleontology in beijing discovered the fossil of a dinosaur with the answer eutyranus
21:52its body is about the size of the famous t-rex it was almost nine meters long and weighed almost 1.5 tons
22:03so we're talking about a giant
22:07approximately 125 million years old this is one of the oldest fossils that shows non-flying dinosaurs with
22:15feathers here are you tyrannus's feathers you can see their length on these
22:21blocks of sediment we can see that you tyrannus's body was covered in feathers from head to tail
22:30but they don't look anything like bird feathers we see today they appear to be more like hair
22:38the most likely hypothesis is that there was a cold spell at the beginning of the cretaceous period
22:44euteranus is in a way the woolly mammoth of that time
22:48with long fine feathers that meant it could keep warm acting almost like down it's been nicknamed by
22:56scientists dino fuzz a stark contrast to the feathers of flying dinosaurs like archaeopteryx and most modern
23:05day birds but with a wealth of feathered dinosaur fossils found in just a few years scientists have pieced
23:13together a timeline of feather evolution the earliest feathered dinosaurs like euteranus had straight
23:21feathers in the next generation of dinosaurs these long hairs separated producing simple branches
23:30in many lineages this down then evolved into more complex feathers with a central spine barbs and then
23:37barbules fitted with small hooks holding them together to form a sail a more familiar symmetrical feather
23:47but only asymmetric feathers shaped more like an airplane wing are capable of creating pressure
23:53differences and therefore lift allowing for flapping flight over long distances
23:59we know the changes that took place but the question remains why did they happen and when
24:07fossils from liao ning once again provide clues suggesting that the ancient bird species confucius
24:14ornus had another use for its feathers confucius ornus is a really special bird it's represented by
24:22more than a thousand specimens and some of them are exquisitely preserved with so many fossils of this
24:30kind of bird researchers around the world have come together to work on this project
24:38we realized that there were two types of specimen within the species some with very long tail feathers
24:44and others with very short tail feathers so we asked ourselves why
24:52so people postulated that one of the morphs was a male and the other one was a female but it
24:57couldn't really be very sure about it paleontologist anna suya shinsami turan looked inside the bone
25:05taking a less than millimeter thick slice to search for answers and one of the first specimens
25:11as section actually happened to be one that had the most unusual bone tissue inside its marrow cavity
25:19which we call medullary bone that's the brown area on this slide the medullary bone is so
25:26interesting because you only find it in female birds and they form it at the time that they're ovulating
25:34and they use that medullary bone to calcify their eggshells
25:39so when i found this i said oh my goodness i didn't know which specimen it had come from because
25:46i only had a little bits of bone and so i contacted my colleague and i said can you double check the
25:51specimen number and see whether the specimen has long tails or no tail and he came back to me and he said
26:00actually the specimen doesn't have any feathers so we could say for sure this was a female confucius
26:08ordinance that meant the long tail feathers belonged to male confucius ornus not needed to aid their
26:15flight the feathers likely served a different purpose in these marshy landscapes of northeast china 120
26:24million years ago it's mating season confucius ornus females have a lot of options and the males have to
26:33redouble their efforts to attract them competition is fierce as they use their spectacular tail feathers
26:40to attract the best mate ornamentation in dinosaurs potentially led to feathers that eventually supported
26:47powered flight then the hypothesis is that you already have these aerofoils these surface areas
26:54and so even though their primary function was ornamentation they must have had some incipient
27:01locomotor function even though they can't fly they still use their wings for their terrestrial
27:06locomotion and then eventually as these wings evolve to be bigger and bigger and have greater
27:11and greater aerodynamic benefit they eventually reach a point where they can be used for power flight
27:16today bird flight is spectacularly complex they soar with ease but the transition from a ground-based life
27:27to one in the skies would not have been an easy one it's something that scientists are still trying to
27:33understand which of the newly found feathered and sometimes winged dinosaurs could fly
27:39how did they take that glorious first leap
27:49surprisingly the oldest missing puzzle piece collected over a century ago archaeopteryx is still filling in
27:57gaps today
28:02in a synchrotron particle accelerator larger than two football fields scientists are analyzing this
28:09precious fossil
28:13the synchrotron beam comes in through that little window it will interact with our object in this
28:18case a fossil and the images are recorded by our detectors they fire a beam of x-rays more than a
28:26million times brighter than the sun at the fossil because the synchrotron beam is very intense
28:33we can get a signal strong enough to penetrate the entire width of the plate
28:36and virtually extract the fossil from the rock
28:41this creates a 3d model with resolution down to one thousandth of the thickness of a hair
28:47when we first saw the images we immediately realized that the bone walls of the humerus and the ulna
28:53archaeopteryx look a lot like those of flying birds
28:56the bone walls are thin and hollow just like those of modern birds
29:01that was our first indication that archaeopteryx must indeed have flown
29:08as far back as 150 million years ago dinosaurs ornamental wings are already evolving for gliding
29:16to fly archaeopteryx has to project itself from a high point
29:27it uses its clawed fingers to climb
29:31from its high vantage point it can spot its prey very easily
29:36and pounce on them simply by spreading its wings
29:39but to truly conquer the skies gliding birds needed to learn to flap there are several ideas
29:47of how this happened the first known as the tree down hypothesis suggests that tree dwelling birds
29:54flap their wings to cushion their landing the second known as the ground up hypothesis emphasizes the use
30:01of wing flapping associated with running to escape danger or catch up with prey
30:09but recently another theory has been suggested one that can be seen in birds today
30:21so these are our performers today and this is olympia and gray here this is annie and brown
30:27and this is twinkle jemima or twinkie for short to analyze the movement of the wings in detail
30:33evolutionary biologist ashley fears needs to see them in slow motion here i've got my high-speed
30:39video camera and i can visualize what the camera is seeing on the laptop
30:46and so you can see that she's really using her wings to break as she gets ready to land there
30:52i actually spend a lot of my time working with developing birds or baby birds
30:56because it can also tell us a lot about the evolution of flight and in many ways they look
31:00similar to some of the fossils that we see that are documenting this origin of flight and so
31:06in these developing birds we have this really interesting system where we can see in real time
31:12how a living animal goes from a flightless animal to a flight capable animal and everything that happens
31:18in between both anatomically and behaviorally
31:21one of the behaviors seen is wing assisted running on an inclined plane
31:28so on the left here we have a four day old tricker partridge it is flapping its wings to
31:33really drive itself into the substrate here and increase traction with its feet so that it can
31:39ascend this deep incline this is not the only behavior that hints that dinosaurs were able to
31:44develop flapping flight they may use their wings to leap into the air and fly either for a very short
31:50distance or for thousands of miles they also use their wings to come down out of trees or off of
31:56elevated surfaces even to swim either across the water or below the water and so living birds show
32:02us that you know they use lots of different habitats and they use their wings for lots of different
32:06functions bird flight developed as an adaptation to the environment as well as to allow gliding down from
32:13trees or to evade predators on land but what exactly was this great environmental change and when did it
32:21allow birds to take the final leap to full flight one site in particular could transport us back to a
32:28time when birds were taken to the skies it's amazing to be driving to las joyas one of the world's most
32:37important early cretaceous fossil sites with some of the most important early evidence of birds from
32:45the age of dinosaurs
32:52after 30 years of excavations an entire prehistoric landscape has been uncovered
33:00we're in what was once a wetland where there is an enormous diversity of species
33:07of both plants and animals and we know that this wetland was freshwater because it was completely
33:16isolated from the sea
33:19paleontologist jesus madogan and his team have uncovered a vast array of plants animals and insects
33:27all part of a complex and thriving ecosystem digs here have revealed thousands of fossils all between 125 and
33:36129 million years old
33:42you see all those crabs there's more of a crayfish
33:44ah each one of those blue marks represents a crayfish
33:48amazing how many there are is more than 500 we have the whole family from the larvae see how small
33:54they are to the juveniles to the adults yeah with all the pincers and everything yeah it's crazy with the uh
34:00you can really tell they're crayfish to process this huge amount of data jesus is combining traditional
34:06observation with the very latest technology smile for the camera
34:14they use a drone to photograph the site and geotags to help recreate a 3d model of the environment
34:20each colored sphere represents a species or family of species the connections between these spheres
34:30indicate interactions the birds of los joyas are found here in this orange section the largest ecosystem
34:39it tells us that the birds were not just passing through they were an integral part of the ecosystem
34:51given the rarity of bird fossils the sheer number found suggests that birds were thriving here
34:57but that's not all these fossils paint a picture of archaic birds that are adapting to geologic change
35:06around 175 million years ago the supercontinent known as pangaea broke up
35:12new continents emerged and oceans and seas rushed in through the fault lines
35:18these new territories with their temperate climate gave rise to flowering plants which provided a new food
35:24source those plants diversified all kinds of insects diversified alongside them to pollinate the flowers
35:32and so birds were probably part of this general diversification of life that started with plants
35:38and bugs and reached all the way to the dinosaurs
35:46lasoyas shows archaic birds evolving right before our eyes
35:50and a class of ancient bird called the enantiornithes is a perfect example
35:57wow
35:59so this is a law love us that's it the original a beautifully preserved skeleton
36:05three-dimensional percent you can see all the bones of the four name
36:09a walla lavis is one of these enantiornithes and it's exceptional in more ways than one
36:15in particular it has developed a highly sophisticated wing a walla lavis this complicated name has some
36:24important connotations yeah exactly this fossil bird back in the day when it was described was the first
36:31primitive bird that preserved the alula the alula is a small mini wing on the leading edge of the main
36:37wing it allows the bird to increase lift at will
36:41this appendage gives the bird great maneuverability in flight and for takeoff and landing
36:47it's incredible that this alula which of course helps birds be more maneuverable in flight was
36:53present in a walla lavis because this fossil is 129 million years old yeah so that of course tells
37:01us that this structure has been around in bird evolutionary history for at least that long
37:06thanks to this dexterity and flight a walla lavis is better able to spot its prey and swoop down upon them
37:18this is not the case for all winged creatures that populate the eden of las hoyas
37:25europa hara a gigantic pterosaur with a wingspan of two meters needs plenty of space on the ground to take off and land
37:33and when danger strikes that can be the difference between life and death
37:40we call this convergent evolution each time flying evolved in animals whether it be birds bats ancient
37:48flying dinosaurs the wings evolved on the upper limb on either side not one on the head one on the tail or
37:55the foot or whatever they evolved using the upper limbs for flights in this world 130 million years
38:03ago dinosaurs flying reptiles archaic birds and ancestors of early modern birds all shared the skies
38:11together this was bird life at its peak a plethora of archaic species living in trees perfectly adapted to
38:21their environments birds birds were taking over the skies but it wasn't to last a cataclysmic event shook the planet
38:33a gigantic asteroid six miles in diameter collided violently with earth
38:40forests burned and volcanic ash soon filled the skies blocking out the sun
38:44this was an extreme survival situation one that 75 percent of earth's species weren't ready for
38:53among the mammals the smallest some weighing less than one pound managed to escape the catastrophe as
39:00well as some reptiles like turtles and crocodiles birds were also hit hard only the smallest such as
39:07asterionis survive the chaos how is it that all but one group of birds were wiped out what did they have
39:14that no other archaic bird and no other dinosaur had
39:21janavis is a bird that did not make it its fossil dates back 67 million years to a time just before
39:28the asteroid hit close analysis is helping us to better understand the reasons for its disappearance
39:37here you can see the skeleton of janavis we have some of the bones particularly the arm bones and part
39:43of the vertebral column equipped with teeth janavis has an imposing stature is this why it didn't
39:51survive the asteroid strike the key difference between janavis and asterionis is size asterionis is much
39:59smaller a trait that was key to its survival post asteroid strike so larger bodied animals through this
40:07mass extinction event didn't do very well at all so a really big bird like janavis probably would have
40:14been at a major disadvantage compared to asterionis after the extinction event getting a meal for an
40:20animal the size of janavis probably would not have been a very easy thing to do they also had very
40:26different ecologies that's true janavis was basically a seabird like we would have been fishing and
40:31eating fish and squid asterionis was more like a generalist ground dwelling bird eating whatever he
40:37found in the beach with the trees gone a large number of tree dwelling birds could not survive
40:45instead it was ground dwellers like asterionis that held the advantage
40:49archaic birds although more numerous were devastated by the asteroid their ecosystems were destroyed
40:59in this hostile environment their imposing size life in the trees and specialized diets led to their
41:05extinction only modern ground nesting birds with more flexible diets were resilient enough to survive a
41:13decimated landscape the sun starts to shine again the dust has cleared and it illuminates a world that's
41:23devastated a world that's almost empty there's no t-rexes anymore no triceratopses anymore most of the
41:29other birds were gone as well and so this would have been a world of abundant opportunity open frontiers
41:37in the million years that follow this apocalypse new ecosystems emerge out of the ashes of the dinosaur
41:46world plant life reappears and a whole system of co-evolution between flora and fauna erupts
41:56with little competition the surviving birds enjoy unprecedented evolutionary success
42:01those few survivors then exploded into new species with the opening up of new environments to become
42:12most of the 10 000 species we see today
42:19a site in denmark bears witness to this key moment in bird evolution on an inland island to the north of
42:26the jutland peninsula lies a geological formation dating back 55 million years
42:34made up of more than 180 layers of marine deposits and volcanic ash these mineral strata form
42:40the cliffs of the small island of fir hundreds of bird fossils have been unearthed in this geological jumble
42:48many of them are birds related to today's cranes and rails
42:52they show that birds had begun to thrive once more at least on the ground but were birds back in the
42:58trees by this time to understand that we need to find birds with more complex feet specialized for
43:06grasping and perching in trees there is one that indicates this change in behavior this one actually
43:14looks very interesting and it seems like it's got a more complex foot that might be specialized for
43:21grasping so it's not like a modern perching bird's foot where you have one two three forward and one
43:28backwards it looks like it's probably got two toes pointing forwards and two pointing backwards and that
43:35is the condition that you see in a few modern groups of birds including woodpeckers parrots and cuckoos
43:42the fact that this bird seems to show pretty clear specializations for perching in trees tells us
43:48that by 55 million years ago this lineage of birds was probably already experimenting with a tree
43:54dwelling lifestyle 10 million years after the asteroid hit the surviving modern birds have diversified
44:03new species have appeared they have adapted to colonize trees once more they diversified like crazy
44:12and most of the birds we know today everything from ostriches to emus to hawks to hummingbirds to owls to
44:22songbirds and everything in between emerged during those manic years decades centuries millennia after
44:32the asteroid impact cleared the deck in certain regions of this reborn world and because of
44:41their geographical isolation some small surviving birds grow impressively large reaching gigantic
44:49proportions they evoke the ghosts of carnivorous theropods one in particular appears to be especially
44:57intimidating the huge bird named gastornis was discovered in the paris basin in 1855 it was so big
45:12people assumed it was a fierce predator but was it if so why doesn't it rule the roost today
45:20the reason we wanted to do this research was that in the 90s two american studies came to
45:28two diametrically opposed conclusions one team said it was herbivorous the other team said it was
45:33carnivorous with the advancements of paleontological tools we thought we'd finally be able to answer this
45:38question definitively after crushing the fossil gastornis bones pale ornithologist delphine angst extracted
45:47carbon-13 so that it could be measured using a mass spectrometer we quite literally are what we eat
45:53and levels of carbon-13 correspond to the amount or lack of protein in our diets that's it everything's
46:00way we can start the manipulation great the spectro is up and running we're ready to go perfect
46:08the carbon-13 analysis of the gastornis bones showed us without any ambiguity that it was clearly a
46:13herbivore combined with other results we already had it showed us that gastornis was 100 percent a
46:19herbivore and there's no possible doubt about it gastornis was a peaceful herbivore it didn't run but
46:27walked despite being nearly seven feet tall and weighing more than 400 pounds it was not a terrifying
46:33predator it disappointed a lot of people that were sad that the image of gastornis chasing little horses
46:41through the forest was wrong my husband's still mad for several million years it walked its clumsy way
46:49across europe and north america but as with any great story the fate of birds was to change again
46:5840 million years ago the continents collided allowing species to move into new landscapes
47:04previously isolated territories were populated by new arrivals including newly evolved predatory mammals
47:12a terrible threat to the peaceful giant gastornis
47:18faced with these faster creatures and despite their imposing size these large birds are not
47:24sufficiently armed to compete they are doomed to extinction
47:29a recent discovery indicates that other giant birds suffered the same fate as gastornis
47:40found in new zealand kumimanu was a giant penguin as revealed by its flipper bones
47:46and you can see here a humboldt penguin that's your average size penguin today
47:51an emperor penguin which is the largest species alive today and then this behemoth here is kumimanu
47:56so it's quite an impressive bird by looking at the proportions the thickness the length of the
48:02width of this specimen we can estimate the body size and so we believe kumimanu probably weighed about
48:08150 kilograms that's 330 pounds in the first 15 million years after the asteroid hit birds are triumphant
48:19they reclaim the reborn forests and become rulers of the skies and seas
48:24however many of the giants like the colossal penguin and the giant gastornis eventually disappear
48:31competition with mammals is sounding the death knell for these great birds
48:35resistant to the many climatic changes that the earth would subsequently undergo
48:40today there are four groups of birds
48:43land higher land birds water birds the group that includes the columbia forms that's pigeons and so forth and
48:51flamingos and a group that includes the hummingbirds and one subgroup in particular has achieved
48:58astonishing evolutionary success in recent times this is the great family of passerines
49:05nesting in our towns parks and gardens passerines are part of our daily lives singing birds that
49:11perch in trees they demonstrate extraordinary adaptability
49:15contrary to the saying sparrow's brains are actually quite powerful
49:22pretty good diversity of birds around lizzie yeah i think most of them are probably passerines
49:27yeah that makes sense i guess passerines are the most diverse group of birds in the world right
49:32how many species are there there are more than 6 000 which is more than half of living bird diversity
49:37today that's a great view of eurasian magpie up there yeah that's a really nice representative of a
49:45big group of passerine birds called corvides and corvids in general i guess are probably most famous
49:54for having some of the very largest brains compared to body size of all birds so these are things like
50:00crows jays ravens and magpies just like this one which make them some of the most intelligent birds
50:08in the world so it's easy to think about magpies and their relatives as the hominids of the bird world
50:13yeah the smart ones exactly passerine intelligence is illustrated by their behavior
50:21the construction of their nests their exceptional memory and their ability to communicate through song
50:27a skill they share with us humans despite our evolutionary paths diverging some 300 million years
50:35ago something happened in nature to get this convergence to be similar between humans and
50:43these martin birds so what we and others had found is that in our four brain area evolved this new
50:52circuit and that circuit evolved in a similar way with a direct connection to the voice circuit in
50:58songbirds humans parrots and hummingbirds why only these few species to evolve vocal learning you're more
51:06likely to be eaten and you won't survive only if you're at the top of the food chain or near the top of
51:12the food chain you can we found that songbirds and parrots evolved from apex predators
51:26birds are beautiful examples of evolution's power to create variety today there are more species of
51:33birds than there are mammals or any other terrestrial vertebrates they thrive around the world perfectly
51:41adapted to the tremendous diversity of environments and landscapes
51:48birds are incredibly successful today and i think it is a really neat fact of life that there are
51:54double the number of bird species than mammal species and by that measure the age of dinosaurs still
52:01continues today long live the dinosaurs
52:15Transcription by CastingWords
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