邹晶梅 Fascinating Early Birds
导语：Everyone’s life is a unique journey. The destination is not all that matters – how we get there is really the best part. 作为中国科学院最年轻的外籍研究员之一，Jingmai充满了科学家的浪漫主义情怀。中美混血的她，在母亲的影响下爱上了中国，爱上了中国的文化。在中国科学院古脊椎与古人类研究所，她参与周忠和院士的研究团队，并与中国的远古热河鸟结下了不解的情缘。
Everyone’s life is a unique journey每个人的一生都是一场独特的旅行。
The destination is not all that matters – how we get there is really the best part! Our unique experiences make us special and create important human diversity.目的地并不是最重要的，沿途的风景才最值得我们去享受。旅途中那些特别的体验让我们的生命变得独一无二，让这个世界变得丰富多彩。
I’m a paleontologist [gushengwuxuejia], which means I study the remains of extinct animals that are preserved petrified as fossils. 我是一名古生物学家，我的研究对象是那些已经灭绝的动物所遗留下来的化石。
Most paleontologists grew up loving dinosaurs as kids, but I found my passion a little later in life. Today I would like to tell you about my journey that brought me here to China.
Even if it's a little cliche, I have to say my mother is my biggest role model. She is also a Professor of Geology [dizhixuejia], My mother grew up in HK the daughter of Shandong refuges. She went back to school to do her phd in geology at the age of 40, which having done a phd myself, I know is no small feat when you have four kids! She also did hers in record breaking time!
Geology had been her passion when she was young and her choice to follow her heart and do what she loved has always been a major factor in my own life choices. Growing up in LA we only used kuaizi at home and we celebrated Zhongqiujie and Chunjie every year. I grew up fascinated with my Chinese cultural heritage, I found it so beautiful and exotic. In 2001, the year I graduated High School, our whole family came to China. This trip changed my life – I loved it even if then when I tried to buy clothes they would tell me I was too fat – I decided I wanted to live in China one day. And my big brother loved it so much he didn't return to America with the rest of us and stayed for over 12 years!
Before I could make this dream of living in China come true, I had to attend University, during which I came across a wonderful mentor. He worked really hard to be a good teacher and you could see he genuinely loved what he did and wanted to share his love of paleontology. His name is Don Prothero and I would probably not have become a paleontologist if I hadn’t become infected with his passion.
I have to say, the cliché is pretty accurate: choose a career you love and you will never work a day!
I study the earliest birds [guniaolei] and how they evolved from dinosaurs over 150 million years ago. Over half of all known Mesozoic bird fossils are from China making it the best place in the world to study their evolution.
This is a reconstruction of the 120 Ma Jiufotang avifauna, the most diverse Cretaceous fossil avifauna known to science. It is the youngest and most diverse stage in the famous Jehol Biota[reheshengwuqun], the richest vertebrate lagerstatte known in the world, which is found primarily in Liaoning province, but stretches in all directions.
This avifauna includes all known groups of Early Cretaceous birds living side by side, such as:
the primitive Jeholornis [reheniao], which ate seeds and had small teeth. Like non-avian dinosaurs Jeholornis had large clawed hands and this long reptilian tail. However, Jeholornis had an unique tail feather morphology consisting of essentially two different feather tracts and we hypothesize that this very primitive bird was actually a pretty capable flyer. 热河鸟是一种原始的鸟类，它以植物种子为食，牙齿很小。类似于非鸟恐龙，热河鸟的前肢上也具有很大的爪子，以及长长的尾巴。然而热河鸟具有独特的包含两种不同羽束的尾羽形态，于是我们推测这种非常原始的鸟类已经具有了相当的飞行能力。
Confuciusornis [kongziniao] is the most primitive bird with a beak and an abbreviated tail ending in distally fused vertebrae, both features present in all living birds. These birds also had sexually dimorphic plumage like many living birds do. The males had elongate ornamental tail feathers that were not present in the females.
The largest Early Cretaceous bird was Sapeornis [huiniao]. This bird had small teeth and ate seeds that it digested with gizzard stones similar to living herbivorous birds. It had very long wings, good for flying, and the hand only has two claws, so the hand is getting smaller, more similar to living birds. However, it had no sternum [xionggu], which forms the anchor for the flight muscles in living birds, making it a puzzle how this bird was able to fly, although we know it could!
In order to understand just how amazing these Jehol fossils are, I need to show you what the typical bird fossil looks like. Of species known from outside China, more than half are known from a single bone or less!! Birds are among the rarest fossils and this is because birds are generally very small, restricted in their terminal body size by the aerodynamic limitations of flight. In addition, bird bones are very delicate and hollow; this is in order to reduce body weight for flight, but more than that birds actually have extensions of their lungs that fill these hollow spaces in the skeleton allowing them to increase their oxygen intake in order to power their aerial locomotion.
So why are there so many amazing bird fossils in northeastern China? To understand this we must first understand a little bit about how a fossil is formed. It relies on the animal dying and being buried before it is scavenged. The Jehol Biota represents an ancient volcanic lake system. Lakes are fed by rivers, which carry sediment as the move, however in lakes the water is still, so as soon as the rivers enter they drop the sediment they are carrying, so that is constantly being deposited on the lake bottom. So a flock of Confuciusornis are flying by and they get caught in volcanic gases and fall poisoned into the lake. They float on the surface for a time but eventually the body sinks to the bottom, where it gets covered slowly but surely by the fine silt carried by the rivers into the lakes. Also important, lake bottoms are anoxic so no scavengers live there to feed off the body so the birds are often preserved absolutely pristine and untouched.
The Jehol lake system was huge and changing its shape during the over 10 million years that it existed from 131 to 120 million years ago. That means there is a lot of rock to search through, and we are still limited to what is easily accessible on the surface of the earth. When we go looking for these fossils we find an area with exposed rock. You break free a big chunk of rock and you turn it on its side, and you hit it with a hammer. This rock will split where there is preserved organic material, because it represents a layer of weakness in the rock.
You can spend weeks even a month, splitting slabs for 10 hours a day in the hot sun and find nothing, it can be very frustrating. The last time I went slab splitting I found nothing and got pretty discouraged, but my boss Zhou Zhonghe must have only been splitting slabs for an hour or two and “oh, look at this beautiful specimen with feathers I found!” Some paleontologists are just born with a gift! Unfortunately I’m not one of those lucky ones. However, even if we relied on the lucky one’s to find us fossils, there still wouldn't be that many, we only spend a month or two each year in the field [yewai]. However, here in China we have the power of numbers! There are thousands of farmers helping us to collect and this has resulted in the biggest known collections of dinosaurs and birds in the world! Did you know there are only 40-something T. rex specimens in the world and only one of them is nearly complete, and it's the world’s favorite dinosaur and we have been looking for this dinosaur for over 100 years! But Anchiornis [Heshijinniao long] was named in 2009 and I recently wrote a paper in which we did a study based on a single collection of 224 Anchiornis specimens! With large numbers we are able to understand much more about the animal, like how it changed with ontogeny, or whether or not its skeleton was sexually dimorphic.
The other amazing thing about Jehol fossils is that they commonly preserve biological traces that are otherwise extremely rare in the fossil record, such as feathers and stomach contents. We really don’t understand the chemical processes that lead to the preservation of soft tissue traces in these fossils. Each part of the fossil represents a unique chemical microenvironment producing different forms of preservation and its incredibly complex.
Each part of the fossil represents a unique chemical microenvironment producing different forms of preservation and its incredibly complex.
One of the most amazing things I have come across is the preservation of the soft tissue of the reproductive organs in several specimens. We stumbled upon these specimens while looking for stomach contents because I’m also very interested in understanding the dietary differences in early birds. Instead we found the remains of ovaries preserved in birds 120 million years old! This is the first time the soft tissue of the reproductive system has ever been preserved, although scientists have tried to understand the reproduction of dinosaurs through their eggs and nests for over a hundred years. Living birds are the only amniotes with only one functional ovary – everyone else has two, including closely related non-avian dinosaurs. These incredible bird fossils, which we published in a paper in Nature, showed that even the earliest birds were modern in this respect, having only one functional ovary. This supports long standing theories that the right ovary was lost in response to the evolution of flight. However, because early birds were more like dinosaurs in that they grew for many years, whereas almost all living birds reach adult size very quickly in less than a year, there are still differences in the ovaries of early birds compared to living birds related to the lower metabolic rate of these taxa. Thus these fossils show us an intermediate condition.
In my current research I study early birds from as many perspectives as possible. I continue to work on new specimens preserving ovarian traces to study the evolution of reproductive behaviours, and specimens preserving stomach contents to understand the evolution of diet in different groups; I use histology to understand how the early birds grow; and I study preserved feathers. We are even now able to know what color these extinct birds were by studying the feathers under a scanning electron microscope. The color forming organelles, called melanosomes, are preserved, and unique shapes indicate different colors.
As a result of this new research I had to contact my artist friend Mr. Rothman and tell him that all these beautiful colors he painted these birds in maybe inaccurate. So far, the only colors we have evidence of at this early time are black, brown, gray and reddish browns, melanosome based colors.Bright colors like greens and yellows are created structurally in forms that are not likely to preserve visually.However, new techniques are constantly becoming developed and one day soon we may even be able to detect structural colors. Right now and especially in China its a really exciting time to study birds.
However, new techniques are constantly becoming developed and one day soon we may even be able to detect structural colors. Right now and especially in China its a really exciting time to study birds.
I love my career but what about I love about my life is not unique to paleontology, it's Science. There is something really exciting about contributing to the knowledge of mankind. To take an unknown, a question, and to be the first to answer it! And the more you learn the more you become aware there is to learn. I’ve always been surprised to learn how much we don't know – there are interesting questions to answer in every field of study. The more questions you have, the more you want to uncover – and this powerful desire to learn more keeps the world a really exciting place!As a scientist you have the opportunity to travel the world for conferences, collaborations, collect data. I’ve collected fossils in Xinjiang, Inner Mongolia, Outer Mongolia, Africa! I’ve been invited to speak in Chile, Japan, the UK; you meet interesting people from all over; I have collaborative projects with Russians and South Americans; and I just put together a killer grant with a professor from Qinghua to study flight biomechanics. As a scientist there are a million paths you can take… and there is an ever-expanding world full of mysteries to inspire you.I am very passionate about what I do and I hope that you also find your passion. XiexieDajia!