In the 1990s, western scientists were allowed to study a series of fossils
from a dig site in west Liaoning, China. What they saw would blow their minds:
One of the most famous fossil beds ever discovered in history.
A finely preserved slice of life from 120 million years ago.
And within this treasure trove,
a unique creature. A dinosaur that would make headlines around the world.
I have been a dinosaur fan ever since I was a kid. I am excited
to dive back into the field once more. In this video, we are going to look at China's
contribution to our understanding of the dinosaur theory of birds.
If you are like me and the rest of my generation, most of us have not really
read up on dinosaur literature since the first Jurassic Park movie. You should dive back in.
A lot has happened since then. Like a whole lot.
One big thing that happened has to do with the dinosaur and bird connection. Birds are
now dinosaurs - feathered theropod dinosaurs - and the only living ones left on earth.
Which I am still getting used to, to be honest. It's the Pluto thing all over again.
The journey towards this understanding takes a long and winding road.
The Wikipedia article on the origin of birds is very well documented and a good place to start.
If you like dinosaurs, then I recommend that you check it out. But let’s do the quick rundown.
In the mid-1800s, the discovery of Archaeopteryx - until a few decades ago
the earliest known bird - sparked debate about the connections between birds and reptiles.
Thomas Huxley, biologist and a contemporary of Darwin,
proposed the animal as a transitional fossil between the two.
The theory lost steam in the 1920s after Denmark's Gerhard Heilmann wrote a book
called "The Origin of Birds". In this titillating tome, Heilmann concluded that though there were
many similarities between birds and dinosaurs - the former did not descend from the latter.
The primary reason for this was because that scientists at the time believed that dinosaurs
had reduced, insignificant clavicles while birds did not (i.e. they had wishbones). Heilmann,
like many others at his time, believed that evolution was not reversible.
Thus he had to conclude that birds and dinosaurs were cousins - sharing
a common ancestor - rather than having a direct link.
Heilmann's work stood as the generally accepted theory for four decades. Then in the 1970s,
two broad shifts in the academia helped revitalize the bird-dinosaur connection.
The first shift began with the work of John Ostrom.
He discovered and described a new family species of dinosaur,
Deinonychus. This large powerful predator forced scientists to revisit their assumptions of what
dinosaurs were and how they acted. For instance, whether they were cold blooded or warm blooded.
The animal's similarities to modern birds and Archaeopteryx,
especially in the forelimb bones, revitalized the dino-bird descendant hypothesis.
This work came along at a time when the academic community started to adopt a classification
methodology called cladistics. This groups together species using their "derived traits"
with the idea of discovering the "most recent common ancestor".
Together, these kicked off the dinosaur renaissance. Support for the dinosaur-bird
theory continued to grow over the years. But scientists waited for a piece of evidence,
some special fossil, to finally glue it all together.
In the 1700s, during the Qing Dynasty, the ruling Manchu emperors would escape Beijing's
searing summer heat at a beautiful Mountain Resort in the city now known as Chengde.
Not to be confused with the city of Chengdu in the Sichuan province.
Chengdu has pandas. Chengde has dinosaurs.
The Manchu had conquered the area prior to their conquest of the Ming Dynasty.
The resort took 89 years to build and is today a tourist attraction.
After the fall of the Qing in 1911, the Republic of China created the ReHe Special
Area out of the region. ReHe, which literally means "hot river" because the area's rivers at
the time did not freeze in the winter, was romanized as Jehol. Later on in the 1920s,
the ROC government upgraded the Special Area to a full province: the Jehol Province.
It was around then that scientists first began to notice that Jehol's lands yielded some excellent
fossils. The American paleontologist AW Grabau proposed the "Jehol series" of fossils in 1923,
on the basis of a Lycoptera fish fossil he discovered near what is now the city of Lingyuan.
When the Japanese Empire illegally annexed the Jehol province in 1933 - an
act that would eventually lead to the Second Sino-Japanese War - their scientists also noted
this rich trove of fossils. Their findings, however, were lost during the chaos of war.
The Republic of China recovered the province after World War II,
only to lose it along with the rest of the mainland shortly thereafter.
After the founding of the People's Republic of China, the government reorganized the provinces.
Jehol was abolished and its land was divided amongst the modern day provinces of Hebei,
Liaoning, Inner Mongolia, and Tianjin.
In 1962, Chinese paleontologist Gu Zhiwei would propose the existence of the Jehol Group. Or
the Jehol Biota - since the fossils included plants.
The Jehol province no longer existed, but the name harkened back to the 1928 discoveries.
For the next few decades, only Chinese scientists were allowed to study the area's fossils.
Then in the 1990s, China opened up to the rest of the world and western scientists
were granted the opportunity to scrutinize its treasures. And what treasures they were!
The fossils in the Jehol Biota are of animals living during the Mesozoic Era - an era that
can be further subdivided into the famous Triassic, Jurassic, and Cretaceous periods.
The era is known as the Age of the Conifers.
Better known as the Age of the Reptiles. Yet better known as the Age of the Dinosaurs.
Today, the Jehol province has cold, dry winters and warm,
humid summers. 125 million years ago in the early Cretaceous period,
the whole area was covered with forests, streams, and freshwater lakes.
Volcanoes to the west would occasionally erupt, throwing huge plumes of ash and
chemicals into the air. Analyses have found these plumes to be made up of hydrogen fluoride,
hydrogen chlorine, and sulfur.
These hydrogen fluoride plumes would suffocate huge bunches of animals and cause them to fall
into the water in mass die-offs. In some areas as many as one animal every 1-2 square meters.
Then the streams would gently wash the corpses into the lakes,
where the falling ash quickly buried them in sediment almost a thousand feet thick.
The sudden, universal nature of this event means that animals
died without being scavenged in ideal preservation circumstances.
Scientists have described it as a Mesozoic Pompeii and I have to agree.
Fossil traits include feathers, skin, muscles, eyes, and even the ovarian follicles of birds.
Fossilized melanosomes allow us to reconstruct the coloring of certain animals.
Even stomach contents were preserved, giving us a glimpse into what these animals hunted
and ate. Thanks to these fossils, we now know, for instance,
that large Mesozoic mammals - shrew-like things 3 feet or 1 meter long - ate baby dinosaurs.
And the biota's diversity was stunning. Scientists have found fossils of mammals, insects, plants,
fish, salamanders, frogs, crocodiles, lizards, pterosaurs, clams, snails, and turtles.
But some of the most impactful fossil discoveries
have been those of both early birds and feathered dinosaurs.
In 1993, Chinese paleontologists Hou Lianhai and Hu Yoaming received a fossil from a collector. The
collector had found it at a local flea market in the town of Sìhé 四合 in the locality of Beipiao.
They determined that the fossil belonged to a species of early
birds. And not just a new species, but a whole new grouping of species or genus.
They named this genus after Confucius:
Confuciusornis. The Chinese name is 孔子鳥, literally Confucius bird.
For the sake of my sanity, I am going to refer to this grouping from now on as the Confucius birds.
Confucius birds existed about 130-120 million years ago.
Its bird-ancestor Archaeopteryx lived some 30 million years prior.
They look like ravens and generally are about the size of a pigeon. We call it an early bird,
but by this time Confucius birds already shared many traits with today's birds.
It is likely that by then,
such bird-ish traits have already disseminated across a wide variety of similar species families.
The animal had a beak without teeth. And it had toe pads and scaly skin on its feet.
And there are great similarities in the wings, though Confucius
birds - like Archaeopteryx - probably did not fly. Likely glided down from trees.
Confucius bird fossils are common in the Jehol Biota and there are over a thousand existing
specimens belonging to many different species. They probably flocked in large groups in the area.
Interestingly enough, many of these fossils have been smuggled abroad
to be sold to private collectors. Since they were fossils of birds rather than dinosaurs,
I reckon they did not fall under the protected import categories.
Okay, so now we have bird fossils. But as I mentioned earlier, Confucius birds did not
pre-date Archaeopteryx. Thus, though it is a very interesting fossil, its discovery did not
really contribute all that much more to what was already known about the origins of birds.
Supposing that birds really did descend from the dinosaurs, bird-ish dinosaurs should
be out there. They needed something more. A few years later, that something came about.
In 1996, two scientists from the Chinese Geological Museum of Beijing
published a paper about a fossil found by a farmer again in the town of Sìhé 四合.
The fossilized animal had feathers. Feathers down its spine and sides.
Unlike the aforementioned Confucius bird though, the writers of the paper did not call it a bird.
Rather, it was a dinosaur. The first ever found with feathers,
and declared to be a transitional species between dinosaurs and birds.
This dinosaur would be named Sinosauropteryx. In Chinese,
they call it 中華龍鳥 or Zhōnghuá lóng niǎo, literally meaning "Chinese dragon bird".
Sinosauropteryx was a compsognathid theropod, a classification of bipedal dinosaurs
with hollow bones and three-toed limbs. Compsognathus were portrayed in the movie
"Jurassic Park, the Lost World". In that movie they were the size of a chicken,
but today scientists believe them to be more like the size of turkeys.
The Sinosauropteryx fossil even preserved the animal's stomach contents.
It had recently eaten a lizard and some eggs.
They were also able to extract information about its coloring. The dinosaur likely had raccoon-like
facial markings and dark-light countershading characteristic of open environments.
Not only did the discovery show that feathered dinosaurs can exist,
it also helped resolve the prevailing rebuttal against the dinosaur origin of birds.
Up until its discovery, all the possible theropod candidates for avian ancestor-ship lived in the
late Cretaceous period. But, Archaeopteryx lived in the late Jurassic - thus a paradox.
Sinosauropteryx helped significantly close the gap,
pushing back the dino-bird transition by millions of years.
The dinosaur made the world news,
and suggested that the lands that would later become China were a center of bird evolution.
Almost immediately after the announcement however, opposing voices emerged to challenge the dinosaur
feather conclusion. They vociferously argued that the fossilized markings were not actually
feathers or even proto-feathers but rather degraded collagen fibers.
Basically something like a frill that you might find on a lizard. The authors argued
that people calling Sinosauropteryx a feathered dinosaur were engaging in wishful thinking.
The debate went back and forth for about a decade, but an influential paper in 2017
settled the matter for the broader academic community.
The authors re-examined some of the comparison evidence the pro-collagen camp had used to make
their argument and concluded that the comparison had been made erroneously.
What we had thought were collagen fibers on ichthyosaurs were scratch marks on fossils.
The community has largely accepted this. Though the debate on the origin of feathers and how they
had been used continues, it is now generally accepted that Sinosauropteryx had feathers.
The 四合屯 fossil site would yield many more famous feathered dinosaurs.
These would provide the most significant evidence supporting the dinosaur origin
of birds. A bevy of early bird and feathered dinosaur fossils.
Notable examples include Protarchaeopteryx robusta, Caudipteryx zoui, Beipiaosaurus
inexpectus, and more. The discovery of the Jehol Biota fossils represented a significant paradigm
shift in our understanding of dinosaurs, and is rightly recorded as such in history.
It continues to yield excellent fossils from many species. And today the site is now the location
of the China Sihe Extinct Organism Fossil Exhibition. A museum is being built there,
to commemorate the groundbreaking science that came out of its lands.