Don't tell me they found Tyrannosaurus rex meat again!

It seems that some scientists are still claiming they can find bits of dinosaur meat clinging to the fossilized bones of ancient dinosaurs. Don’t sharpen your dinner knives yet.

I thought this story, which first appeared in 2007, had died long ago, but it has just reappeared. Before I get to that, though, let me explain the original claims. Back in the late 2000’s, a couple of paleontologists managed to publish two articles in the journal Science claiming they had found traces of original dinosaur proteins in 68-million-year-old Tyrannosaurus rex fossils, and in an even older 80-million-year-old fossil from another dinosaur, a hadrosaur.

This would have been shocking news if it was true, but alas, it wasn’t (even if Jurassic Park fans wished otherwise). Organic material survives only a very short time after an animal dies, usually just a few years. Bones and teeth can last far longer, though. Scientists have extracted DNA from the bones of Neandertals and cave bears that are over 50,000 years old, which is pretty extraordinary.

But 68 million years is far, far longer than 50,000 years. Those fossils are one thousand times older than bones from Neandertals.

But maybe proteins can last longer than DNA? Well, perhaps, but not that long. The oldest known protein fragment, which was preserved in an exceptionally cold environment, is about 3 million years old. The T. rex fossils studied in the Science paper were found in a warm climate, where any proteins must have degraded far more quickly.

I wrote about this way back in 2008, expressing my disappointment with the journal and explaining some of the problems. Nature ran a news story about the controversy as well.

But wait, you’re probably thinking, that T. rex study was published in a prestigious journal, so how can it be wrong? Well, what seemed to happen was this: one of the editors at Science back in 2007 simply believed the study, or maybe he just wanted to believe it, so he ignored the reviewers. How do I know this? Well, when the first paper appeared, in 2007, two of the scientific reviewers, both experts in the field, contacted me to tell me that they had both recommended rejecting the paper, but the editor went ahead with publication anyway. (They contacted me because I had published papers in Science before, and they wanted my advice on what they could do.)

My guess is that the Science editor wanted to get headlines along the lines of “T. rex tasted like chicken.” (To explain: the tiny fragments of protein that the first paper found appeared to be similar to proteins from birds.) The editor got exactly that, in stories that ran in the Washington Post, the New York Times, Smithsonian Mazazine, and elsewhere back in 2007 and 2008.

After the original T. rex paper appeared, at least two letters were sent to Science explaining why it was wrong. Science published them as a “technical comments,” which weren’t nearly as prominent as the original paper.

That letters gave far more plausible explanations for the data from the paper: first, one letter explained that it was very likely that the tiny, tiny trace of chicken-like protein was simply contamination from a modern bird, maybe as benign as someone’s turkey sandwich. That letter also pointed out that the supposed T. rex protein appeared to be modern in origin, because it lacked the signs of aging that an ancient protein fragment should have. (The details are very technical; follow the link if you want to learn more.) The other letter pointed out errors in the statistical analysis, pointing out that the result could easily be a statistical artifact.

A later paper, published independently, re-analyzed the T. rex data itself and found that the sample appeared to contain “common laboratory contaminants, soil bacteria, and bird-like hemoglobin and collagen.” In other words, no ancient proteins at all.

I should note that the experiments used to detect the dinosaur proteins, using a technology called mass spectrometry, are notoriously plagued by contaminants. Even a tiny trace of a modern bird in the mass spectrometry lab (e.g., someone eating a turkey sandwich) is liable to produce a few protein fragments that show up in the experiment. Scientists at the time pointed out that the very same lab had done experiments using ostrich bones around the same time as the dinosaur fossils.

And if that wasn’t enough, yet another published paper argued that the “soft matter” found in some fossils by the paleontologists was likely to be a bacterial biofilm. Fossils, I should explain, are highly porous, and it’s easy to imagine how bacterial could infiltrate them over the millenia.

In fact, you don’t have to imagine that at all: another scientific paper from 2019, published in the journal eLife, described finding “an abundant microbial community” in dinosaur fossils.

All of this skepticism did not deter the original scientists. It was less than two years before they’d published a second report (also in Science, with the same editor) claiming that they’d found similar proteins in another, even older dinosaur fossil, an 80-million-year-old hadrosaur.

And yes, the paleontologists continued to insist that they found “soft matter” that must have originated from the original dinosaurs. Dinosaur meat! The highly regarded CBS news program 60 Minutes was so impressed that they aired an entire segment on this finding:

Alas, there’s just no way that fossils contain any soft matter from 62 million years ago. It was likely just bacteria. But we can’t let that get in the way of a good story.

So how long can animal proteins survive? In temperate regions (such as those where the T. rex fossils were found), most organic matter decays in a few decades. If the animal happens to die in a very cold place, and its body is encased in ice, it seems that some organic material can survive up to one million years, and possibly even longer. Cool! (Pun intended.)

But the T. rex fossils from the original Science study were found in temperate climates. They were not frozen in deep permafrost or ice, and the original organic material was almost certainly long gone many millions of years ago.

I thought this story was dead, but apparently I was wrong: a small cadre of scientists continues to believe that dinosaur fossils–which are made entirely of stone, not bones–contain detectable traces of the original dinosaur proteins. Unbeknownst to me (because I wasn’t following it), another paper appeared in 2017 that claimed to find signs of dinosaur proteins in a 195-million-year-old fossil, more than twice as old as the previously reported claims.

Astounding, if true. And just this month, a chemistry professor at MIT reported that he has the explanation for how these proteins survived so long. This finding, though, is more about how the chemical bonds in collagen–the protein that bones are built upon–are exceptionally stable. That’s interesting, but it doesn’t at all prove that collagen can last for nearly 200 million years.

So count me as deeply skeptical. The science of dinosaur “meat” has from the beginning been fraught with wishful thinking. Multiple papers appeared refuting the original claims, and none of those were effectively rebutted; it seems they were just ignored by scientists who preferred a more fanciful story. I wish it were otherwise, but fossilized bones from Tyrannosaurus rex and other dinosaurs lost any traces of the original organic material eons ago.

Another humanoid species walked the earth

[I'm on vacation, and this short post will appear while I'm away.]

One of the coolest scientific discoveries of the past few years was a small bone found in a remote region of Siberia.  The scientists who found it initially thought it was just an early human fossil, or else a Neanderthal fossil, but something about it looked a bit off.  It was just one small finger bone, not much to go on.

But DNA sequencing told a different tale.  The bone belonged to a female who was neither human nor Neanderthal, but something in between.  She and her kind appear to be closer to Neanderthals than to modern humans, but there is no doubt that she represents a new hominid species, one that died out only recently in evolutionary terms.  The evidence indicates that this previously unknown group, called the Denisovans after the cave in which the bone was found, actually interbred with humans.

The latest findings were published last fall in the journal Science, by a team led by Matthias Meyer and Svante Paabo.  With just one small, 75,000-year-old finger bone, they knew that extracting DNA would be a challenge.  Most of the DNA from ancient samples comes from bacteria and other creatures that have infiltrated the bone over the millenia.  But they were lucky in one respect: Siberia is cold, and has been for a very long time, which helps to preserve DNA.  Still they had to develop an entirely new method of extracting ancient DNA for this bone.

Meyer and colleagues extracted enough DNA to cover the entire genome of this ancient female.  They estimated that Denisovans and human diverged over 175,000 years ago.  They also discovered that modern Papuans contain vestiges of Denisovan DNA in their genomes, about 6%, suggesting that interbreeding occurred when humans were spreading across Asia.

Just this month, National Geographic's Jamie Shreeve published a feature article on the discovery, providing a fascinating look at how a single finger bone revealed a previously lost sister species.  (I highly recommend it, even for those who read the original Science article.) Now that we know what to look for, we might find more, and learn more, about these almost-humans from ancient Siberia.  And maybe we'll eventually figure out why they disappeared.

A final note: this discovery is yet another example of how evolution has shaped the history of life on this planet, but somehow I suspect the anti-evolution forces in the U.S. will find a way to deny it.