Are chickens the closest living relative to T. rex? You have undoubtedly heard that “fact” bandied about. Maybe you’ve wondered about it. Or maybe you just accepted it as truth because it came from a seemingly reliable source.

Or maybe you’ve bought the idea because it’s such a crazy, cool juxtaposition. There’s sweet Henrietta Honeybunch placidly roosting out there in the coop. And she’s the favorite grandchild of the thundering, carnivorous king of the dinosaurs? How cool! How crazy!

But no. It just isn’t true. Sorry.

But maybe you’ll be consoled in knowing that Henrietta is a genuine, certified dinosaur. My cute, fluffy Silkie hen, Dorothy Laymore, is also a dinosaur. As a matter of fact, all chickens are dinosaurs. So, since T. rex is a dinosaur, there’s a connection! And since all chickens and the late Mr. Rex are also all therapods, there’s an even closer connection.

But here comes the important truth. All birds are therapod dinosaurs. Thus Henrietta, Dorothy and all their chicken friends are no more closely related to T. rex than the robin outside my window or the ostrich at the zoo.

But you know all of this already, right? Because you read Part 1 of this series. If you haven’t read it and feel the need to get up to speed, click back to it and take a look. I’ll wait right here for you. But, please come back, because there’s another import question to be addressed.

The other question: How did the chicken/T. rex half-truth get started in the first place?

I’m fairly sure that I’ve tracked down the series of events that culminated in the publication of some misinformation nearly twenty years ago. From there the misinformation took on a life of its own, and the rumor was out in the world, spreading around like free-ranging hens on a spring day.

The chain of events leading up to the misinformation contains these links:

Discoveries by couple of well-known and respected scientists
The excavation of an important fossil
The accomplishment of some incredible, cutting-edge science
And finally, the misreporting of that work by the popular press.

It is a long story, even in the condensed way I’m telling it here. And, true confession, it’s only peripherally about chickens. But in the process of sleuthing out the truth, I’ve fallen into an incredibly fascinating rabbit hole. And I think you’ll be equally fascinated with my account. I’ll introduce you to some amazing scientists and some of the incredible work they’ve accomplished. And, hey, it’s about dinosaurs! I realize that this is a chicken blog and you come here for chickens. But dinosaurs!

The first link in this fascinating chain of events is undoubtedly the renowned paleontologist Jack Horner.

Jack Horner

It's not surprising that Dr. Horner comes first in a situation involving dinosaurs. Not only has he done some incredible work in paleontology, but if you were to ask a large group of random people to name a dinosaur guy, his name, without a doubt, is the name most folks would produce.

**Dr. Horner** (photo: Creative Commons)

Dr. Horner has spent his entire life doing paleontology. He found his first dinosaur bone when he was eight years old. Since that first discovered bone, there have been many, many more discoveries. And research. And teaching. And public acclaim. One current measure of success and prominence is if one has a Wikipedia page. And of course, Jack Horner does.

The Jack Horner Wikipedia page first mentions his research on Maiasaura, where he clearly demonstrated that some dinosaurs were good moms – that they actually cared for their young.

Then Wikipedia describes his role as the technical advisor for the first five Jurassic Park movies. It has been suggested he’s the model for the character Dr. Alan Grant. And in spite of his long career working with dinosaur fossils, he is probably best known for that - because the awkward reality is that lots of people go to movies and not so many read science journals.

Wikipedia also mentions the “Chickenosaurus Project.” In 2011, Dr. Horner announced that he was undertaking a project to genetically reverse-engineer chickens into dinosaurs. I spoofed the chickenosaurus project in an April Fools post a couple of years ago. Should Jack Horner ever run across that spoof, I hope he realizes that I could not have written the spoof had I not been following his progress. I am, and I will always be an ardent Jack Horner fan.

Mary Higby Schweitzer

Dr. Mary Higby Schweitzer has made some ground-breaking discoveries and almost singlehandedly created the new discipline of molecular paleontology. She obviously has a Wikipedia page, too.

She grew up in a conservative Catholic family, but as a teenager switched to a fundamentalist church that believed in a literal interpretation of the Bible. This church—and Schweitzer—gave no credence to evolution and believed that the Earth was only 6000 years old.

In the late 1980’s, Schweitzer decided to go back to school to add an education degree to her baccalaureate so she could teach science. She started attending classes at Montana State University. One day she sat in on a lecture by Jack Horner. The lecture piqued her interest and afterward she approached Horner and asked if she could audit his class.

In a 2017 interview in Science, she recalled the conversation. "Hi Jack, I'm Mary. I'm a young Earth creationist. I'm going to show you that you are wrong about evolution."

"Hi Mary, I'm Jack. I'm an atheist," Horner replied. But he did allow her to audit his course.

As Horner’s lectures progressed, Schweitzer gradually came to realize the information he was presenting was irrefutable. Evolution was real and the Earth was very old. "He didn't try to convince me, he just laid out the evidence," she explained. But, "it cost me a lot: my friends, my church, my husband." But not her faith. She saw God’s handiwork in the formation of our 4.5-billion-year-old planet and evolution of life on its surface.

Schweitzer also came to realize that her future was in paleontology. She started volunteering in Horner’s lab, and eventually enrolled in a graduate program. Paleontology was changing. With the advent of computers and new techniques, scientists were able to examine dinosaur bones in new ways. For her dissertation, Schweitzer decided to examine the load-bearing bones of large two-legged dinosaurs at a microscopic level. Working with a T. rex femur, she meticulously cut very thin sections—an extremely difficult task with normal bone, and even harder with fossilized bone. Once she could obtain good thin sections, the next challenge was affixing them to microscope slides. Once she accomplished that cumbersome task, she was able to look inside dinosaur bones at a microscopic level. That’s when she saw the blood cells. And that changed the course of her life, her work, and the study of dinosaurs.

What she actually saw were round things that looked just like red blood cells. And they were in exactly the right part of the bone where one would expect to find red blood cells. But that went against everything everybody knew about how fossils formed.

The classic model for how a dinosaur turns into a dinosaur fossil involves these steps: First, the dinosaur dies. Second, the flesh, and all organic matter rots away. Third the minerals of the bone remain and eventually other minerals leach in from the surrounding material. Fossils, the classic model proclaims, are mineral. Red blood cells are organic; thus, they should not exist in fossils.

Jack Horner heard it being bandied about that Schweitzer was seeing blood cells in millions of years old dinosaur bones and summoned her to his office for a discussion. "They are in the right place to be red blood cells. But they can't be red blood cells. We all know that," she remembers telling him.

She recalled Horner’s response in a 2006 interview: “Jack said, ‘Prove to me they’re not red blood cells.’ That was what I got my Ph.D. doing.” She remembers that moment in Horner’s office as a turning point in her life. She realized that science can never produce conclusive proof. That’s just how science works. Science cannot and will not ever prove evolution, a non-flat Earth, the Earth’s rotation around the sun, the presence of red blood cells in a dinosaur bone, or anything. It can disprove it or it can support it. And when something is supported over and over in a variety of ways, it eventually becomes generally accepted.

Schweitzer eventually showed that there were fragments of hemoglobin in the dinosaur bone. Hemoglobin is the main protein found in red blood cells. And then she demonstrated the presence of hemoglobin using a different method. And then again, using another method. And again. A total of six different ways. And she showed that there was no hemoglobin present in the sandstone that had surrounded the dinosaur bone. Those analyses became her doctoral work. She earned her PhD in 1995. And in 1997 she published her work in the Proceedings of the National Academy of Science and created a stir. And then she accepted a position at North Carolina State University.

That Mary Higby Schweitzer was able to demonstrate the presence of organic chemicals in millions of years old dinosaur bone was amazing. But the implications of her discovery were even more amazing. In the final paragraph of her 1997 paper, Schweitzer mentioned amino acid sequencing. Proteins are made up of amino acids. While proteins like hemoglobin are shared by a vast array of animals, the hemoglobin in each animal species is different—the order of the amino acids varies. Amino acid sequences are more similar in closely related species and are less similar in distantly related species.

From the very beginning of paleontology, scientists had constructed dinosaur family trees based on the similarity of the appearance of the bones. Now, the possibility of sequencing proteins found in old bones opened up a new door for determining dinosaur relationships. And, in addition, the protein sequences could be compared to today’s living animals, and the grand scheme of how dinosaurs fit with today’s living animals could be determined. The field of molecular paleontology was born.

B. rex

Jack Horner spent a good portion of his life working the Hell Creek Formation, a fossil-rich area that stretches over parts of Montana, Wyoming, North and South Dakota. The very first T. rex fossil ever discovered (in 1902) is a Hell Creek fossil. And of all the T. rex fossils that have been excavated, many have come from here.

**Hell Creek State Park** (photo: Creative Commons)

Bob Harmon, a member of Horner’s crew, was eating lunch one June day in 2000 in the inhospitable badlands near the Fort Peck Reservoir in eastern Montana, when his trained eye noticed a bone jutting out of a cliff.

In his book, How to Build a Dinosaur, Horner describes how Harmon scrambled up a twenty-foot rise to get a better look, then piled some rocks and placed a lawn chair on top of the rock pile and stood on that precarious construction to take some pictures. He found three other bones, a good indication that more of the skeleton was in the cliff. A promising find!

Horner’s team rolled up their sleeves and got to work on extracting the skeleton. It took years of grueling labor. People and jackhammers were lowered forty feet from the top of the cliff and eventually about half of the skeleton was recovered. It was a tyrannosaur and it was dubbed “B. rex.” The “B.” was for Bob.

After Horner’s team dug each fossilized bone from the cliff, they coated it with plaster to protect it. Because the site was so remote and unreachable, they commissioned a helicopter to lift the excavated bones out. Unfortunately, the final plaster encased bundle of bones weighed nearly one and a half tons – more than a helicopter could handle. They reluctantly split the bundle in two and, in the process, broke the three-and-a-half-foot-long femur. The team carefully collected the femur pieces that had fragmented during the breakage and wrapped them in aluminum foil. It seems tragic that the B. rex femur, after remaining intact for millions of years, had been broken by the scientists excavating it. But breaking the bone also allowed a look inside the bone. And that changed the way we study dinosaur bones and the way we think about fossils. And eventually, it fostered the popular misconception that chickens are the closest living relative of T. rex.

Sequencing Dino Collagen

Dr. Mary Higby Schweitzer was just starting at North Carolina State University as an assistant professor and was happy to receive the fragments of B. rex bone from her mentor. She had been hoping to work with some fresh, well preserved fossil bone that had not had any chemical exposure and these fragments fit the bill perfectly.

And then she did some incredible, cutting-edge science.

One of the first things she did with a portion of the material was to soak it in acid. Acid dissolves minerals, and if one were to subscribe to the classic view of fossils, dissolving a fossil in acid would be pointless and destructive. If fossils are completely composed of minerals, there would be nothing left.

But after the mineral had been dissolved away there was material left! The material was soft and stretchy. It seemed to be organic tissue!

Schweitzer published her findings in 2005 in Science. The paper was entitled “Soft-Tissue Vessels and Cellular Preservation in Tyrannosaurus rex.” In that paper, she noted that under a microscope, the undissolved material showed branching “vessels [that were] flexible, pliable, and translucent.” She noted that “many of the dinosaur vessels contain small round microstructures that vary from deep red to dark brown.” She was careful not to call them blood vessels containing blood cells. But she did report that when she dissolved modern ostrich bone in the same way as the fossilized dinosaur bone, she found that “the vessels and contents [from the T. rex bone] are similar in all respects to blood vessels recovered from extant ostrich bone.”

It seemed that Schweitzer had found organic tissue in a fossilized 68-million-year-old T. rex bone! How could she top that? Well, she could test that organic material for the presence of protein. And, with the aid and assistance of colleagues from a variety of other scientific institutions, that’s what she did. Her 2007 paper in Science, “Analyses of Soft Tissue from Tyrannosaurus rex Suggest the Presence of Protein” revealed that collagen, the main protein found in bone, was indeed present.

And how could she top that? She could sequence the peptides in the collagen. And she could compare those sequences with the peptide sequences of the collagen of other animals. And that would show how T. rex was related to those other animals.

And that’s what she did - with the aid of scientists with sequencing expertise, including John Asara of Beth Israel Deaconess Medical Center and Harvard. The results of that analysis were published in the same issue of Science as the collagen paper and was authored by Asara, Schweitzer and others. The paper was entitled, “Protein Sequences from Mastodon and Tyrannosaurus Rex Revealed by Mass Spectrometry.”

It is an important, seminal paper. Nobody had ever sequenced dinosaur collagen before! But there were problems. Since this was the first attempt ever at sequencing dinosaur collagen, there were no other dinosaur collagen sequences for comparison. In 2007, there weren’t even that many collagen sequences of any animal available for comparison; because the technique was relatively new. Most of the animals that had been sequenced were animals that were commonly used as laboratory animals—like frogs, newts, mice, fish and chickens.

Hypothetically, the T. rex collagen sequence would most closely align with chickens since dinosaurs and birds were phylogenetically similar and chickens were birds. And that is exactly what the results showed. “The small group of peptide sequence data reported here support phylogenetic hypotheses suggesting that T. rex is most closely related to birds among living organisms whose collagen sequence is present in protein databases.” (Bolding is mine, for emphasis.) In this first-of-a-kind analysis, the authors concluded that when comparing the T. rex data with the limited available data from other animals, the closest match was with chickens. And that suggested that among the animals available for comparison, T. rex was most closely related to birds.

It was incredible, cutting-edge science, and it was an amazing paper. And then a lot of people got it wrong!

The Guardian, NY Times, and Others

The popular press realized the importance of the Assara/Schweitzer paper almost immediately. The British newspaper, The Guardian, was one of the first to report on it in its April 12, 2007 edition. The reporting, by science writer Alok Jha, was reasonable and accurate. The article correctly stated that “the research provides the first molecular evidence for the notion that birds are the modern-day descendants of dinosaurs.” The article also offered an important quote from Dr. Assara: "If we had more species in the database to compare it to, such as alligator or crocodile, which have not been sequenced yet, we may also find matches to those species. Based on this study, it looks like chickens might be the closest amongst all species that are present in today's genome databases." (My bolding)

I assume that some editor, and not Mr. Jha, was responsible for the headline and the picture atop the article. The Guardian went completely off the rails with those. The headline: Who are you calling chicken? T. rex's closest living relative found on the farm. The large picture shows chickens and is captioned, “Chickens, now thought to be the closest living relative of the mighty Tyrannosaurus rex.” The headline and picture are often the only thing people see. Or, if they skim the article, they may miss the subtleties and their takeaway will be based on the headline. It is completely misleading. The seventeen-year-old article is still available on-line for anyone to find in a web search.

The Guardian was not the only news outlet that posted a misleading headline that focused on a T. rex connection with chickens rather than birds in general. The April 12, 2007 New York Times headline: T-rex proteins: like chicken. The April 12, 2007 BBC News proclaimed Protein links T. rex to chickens and showed a picture of a chicken next to a picture of T. rex with the caption “the resemblance may not be immediately obvious.” The April 13, 2007 Reuters headline announced “T-rex thigh shows chicken family ties.” The April 15, 2007 Jerusalem Post headline declared, “T-rex found to be related to chickens.”

And so on.

The misinformation was out there, it seemed to resonate with the general public, and it continued to spread. It has continued to spread for seventeen years, and it is still spreading today.

But it’s wrong.

The Emails

I’m sure that you are beginning to realize that the chicken/T. rex misinformation bothers me a lot. Well, that’s true. And it’s obvious. I’ve spent a lot of time writing a lot of paragraphs about it.

But what about Dr. Schweitzer? Her delving inside dinosaur bones has significantly advanced human knowledge. But in the process, she has also unintentionally spawned a persistent bit of misinformation. Is she aware of that? How does she feel about it? I had to find out.

So, I emailed Dr. Schweitzer.

In my email, I outlined specific published instances where the chicken/T. rex connection had been misconstrued. Including The Guardian headline. “Somehow The Guardian and other popular press outlets grabbed information from your research and turned it into the popular misinformation that continues to circulate today: Chickens are practically baby tyrannosaurs! I’m planning an article that will discuss the distortion that T. rex and chickens share a special connection. I would really appreciate a statement from you that I could include in my article. My readers would welcome a few words from you. And I’m pretty sure my chickens would like to have everybody know the truth about their family tree.”

I honestly didn’t expect a reply. The bold truth is this: Dr. Schweitzer is a highly regarded scientist who has done some incredible, cutting-edge science. I’m a chicken blogger.

But as it turns out, in addition to being a highly regarded scientist, Dr. Schweitzer is also a very gracious person. One morning I opened email on my phone and found her reply in my inbox.

Her reply was long, technical, and filled with cladograms from her book Dinosaurs – How We Know What We Know (a cladogram is basically a family tree of animal groups). She’d obviously spent some time putting her reply together. Much of Dr. Schweitzer’s reply focused on relationships between animal groups.

With no preliminary pleasantries, her email opened with “Among all living organisms, you can think of it this way: All living birds share an ancestor in common with alligators more recently than they do with any other group. If fossil taxa are included, we can say that all dinosaurs share an ancestor in common with birds (all birds) more recently than they do with any other group.” She went on to discuss how birds fit in among the dinosaurs. It’s the discussion I covered in part one of this series.

Near the end of her email, she made this important observation: “…and [we use] chickens, because more molecular data are in databases for chickens, than for other birds.” To me, that gets to the whole heart of the misunderstanding. In 2007, when Dr. Schweitzer and her colleagues were doing the first T. rex sequencing work, and even today, there is more information of every kind on chickens than there is on any other bird species. Many, if not most, bird species have never been examined at a molecular level. Chickens are very studied birds! So, of course, they used chickens as their token bird. Why wouldn’t they??

So, while chicken data was used in the 2007 study, chickens were representing birds. A 2008 paper by Chris Organ of Harvard, Schweitzer, Assara, and others that diagrammed the “inferred evolutionary relationships of major vertebrate groups hypothesized from collagen” put T. rex and chickens on the same branch. Ostriches were also included in that study and are also on the same branch. Ostriches are, of course, birds. Birds. It’s birds. Not chickens.

Dr. Schweitzer’s ended her email with these words of advice: “I sure wouldn't waste a lot of time worrying about chickens. What they are trying to say is that birds are a type of dinosaur, just like pugs are a type of dog. And chickens are a bird…Good luck.”

I was deflated. It’s like I’d had a chance to have a conversation with someone I respected and admired and then that person waved as they turned to go. But the wave was dismissive.

I’m pretty sure that what “they” are trying to say with the statement “Chickens are the closest living relative to T. rex” is exactly what they’re saying. When somebody hears that statement without context, they’re going to take it at face value.

Dr. Schweitzer has spent her career defending her work: From other scientists who have been skeptical that she really found intact protein in dinosaur fossils; from critics who say that the protein she found came from bacteria or other contaminants; even from young-earth creationists who argue that dinosaur soft tissue couldn't possibly survive millions of years—her discovery thus proving that Earth is really only 6000-years-old. So, perhaps she views my excitement over the chicken/T. rex misinformation a case of splitting pretty unimportant hairs in the grand scheme of things.

I understand and appreciate her perspective. Dr. Schweitzer is a highly regarded scientist who has done some incredible, cutting-edge science.

But I’m a chicken blogger. So, I care about chickens.

And it’s birds. Not chickens. Birds.