Dinosaur Blood, or Just Fancy Rock?

In 2008, a team digging in a mine in northeastern Brazil pulled a leg bone out of 115-million-year-old rock. It belonged to a young, meat-eating dinosaur about three metres long, roughly the size of a large dog with a tail. For eighteen years it sat in a collection, doing what fossils do.

Then someone put it under a microscope and found tiny round blobs packed inside the bone's blood-vessel channels. They looked a lot like red blood cells. The chemistry around them matched heme, the iron-rich molecule that carries oxygen in your blood.

On 2 November 2026, the result landed in PNAS, and the internet did what it always does. "Dinosaur blood found!" Within days, other scientists were pushing back with "hold on, are you sure those are cells?"

Both reactions are fair. Let's go through what the team actually found, why it's so surprising, and why some of the best people in the field aren't sold yet.

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The find in sixty seconds

Until now, the oldest candidate dinosaur blood cells were from around 80 million years ago. This one would add about 35 million years.

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Why "dinosaur blood" sounds impossible

Think about what happens to a dead animal. Within days, enzymes and microbes start taking it apart. Within years, soft tissue is gone. Within thousands of years, most proteins have fallen to bits. DNA lasts a bit longer in cold, dry places, but not anywhere near tens of millions of years.

So the textbook view for a long time was simple: fossilisation turns bone into stone, and anything organic is long gone. You get shape, but not substance.

Blood should be the hardest case of all. Red blood cells are soft bags of water and protein. They're packed with hemoglobin, a big protein that carries oxygen, and the star of that protein is heme: a flat ring-shaped molecule with an iron atom in the middle. Heme is what makes blood red. It's also a chemically reactive molecule, which is exactly why you'd expect it to break down fast.

One more detail that matters later. In humans and other mammals, mature red blood cells throw away their nucleus. In birds and reptiles, they keep it. Dinosaurs are close relatives of both, so if you're hunting for dinosaur red blood cells, you'd expect a cell with a nucleus. Hold that thought.

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Part 1: What the team did

Grice says her team wasn't even looking for blood. They had a broader question: how much of an ancient animal's original biology can survive fossilisation? So they picked a very well-preserved limb bone and looked at it in several different ways.

Step 1: Look inside the bone's plumbing. Bones have tiny channels called vascular canals, which once held blood vessels. Inside them, the team found lots of small, oval, dented-in structures. They averaged about 23 micrometres long and 19.5 wide.

Step 2: Check what they're made of. This is where it got serious. They combined electron microscopy, Raman spectroscopy and mass spectrometry. Grice stressed one point: they did the chemistry in situ, meaning on the structures where they sit in the bone, rather than grinding up a chunk of fossil and guessing where the molecules came from. That link between "this shape" and "this chemistry" is the heart of their argument.

Step 3: Find heme. The analyses picked up heme B, the form found in hemoglobin. They also found 3,8-diethyl heme B, a compound linked to heme as it degrades during fossilisation. In other words, not only heme, but heme that looks like it's been through the wringer.

Step 4: Compare with the surroundings. The rock around the fossil was full of molecules from microbes, mostly chlorophyll-related compounds. The bone, by contrast, was dominated by heme-type molecules. If the heme had simply leaked in from the surrounding sediment, you wouldn't expect that split.

Step 5: Look for collagen. They also detected hydroxyproline, an amino acid that's a signature of collagen, the main structural protein in bone.

That's a solid package. Grice called it a landmark discovery, and on the chemistry side at least, plenty of experts agree it's a careful piece of work.

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Part 2: How could blood last 115 million years?

Here's the team's best explanation, and it's a fun one.

A manganese mineral may have frozen the moment. The blob-like structures were mineralised with hausmannite, a manganese oxide (Mn₃O₄). The idea is that this mineral formed early, before the cells fell apart, and either stabilised them or made a sort of mineral copy of them. Think of it less like a preserved cell and more like a cast of one, with some of the original chemistry trapped in the mould.

The burial was lucky. The team suspects the animal was covered by sediment quickly, in a spot with very little oxygen, and that microbial mats (slimy films of microbes) grew over the carcass. Both would slow down normal decay.

Don't picture a fresh cell. This matters a lot. The team isn't saying you could open the bone and find intact, living-looking blood. As one summary put it, the cells aren't preserved in their original biological state. Components of their identity appear to have survived inside a mineral framework. It's closer to a fossil of a cell with some chemical leftovers than a blood sample.

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Part 3: Why some experts aren't convinced

This is where the story gets interesting, because the pushback isn't random internet skepticism. It comes from people who've spent careers on exactly this problem.

Mary Schweitzer (North Carolina State University) is the researcher who made "soft tissue in a dinosaur" a serious scientific topic in the first place. She praised the team for bringing rigour to deep-time fossils and agreed that original molecules can persist in some form. But she isn't convinced the images show red blood cells. Her reasons, as reported by Live Science:

• Bird and reptile red blood cells keep their nuclei, which usually gives the cell a visible bulge. These structures are concave and show no such bulge.
• The size and shape don't match what she'd expect from non-mammalian red blood cells.

The team has a reply: fossilisation could easily have squashed the cells out of shape, or dinosaur red cells may simply have looked different. (The two sides actually describe the size mismatch differently in news coverage, which tells you this part of the debate is still unsettled.)

Maria McNamara (University College Cork) called it one of the most thorough attempts at fossil blood cells she'd seen. But she asked whether other sources of heme had been properly ruled out.

Evan Saitta (Field Museum) accepted that heme is there. His question is sharper: are the round things cells at all, or are they just blobs of manganese oxide that happen to be round?

So there are really two separate questions hiding inside the headline:

Grice stands by the interpretation. She argues that location, chemistry and microscopy together point to blood cells. For context, Science reported that at least 14 earlier studies have tried to describe red blood cells in ancient fossils, so everyone in this field has learned to be careful.

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Part 4: This fight has a history

None of this started in 2026.

2005: the T. rex that started it all. Mary Schweitzer's team reported flexible, vessel-like structures and cell-like shapes inside a T. rex leg bone, around 68 million years old. It was shocking. Critics countered that bacterial biofilms (microbial slime) could mimic those structures and that the material might be contamination. Later work from her lab proposed a possible rescue mechanism: iron, from blood itself, may help preserve tissue by cross-linking proteins. This is the thread the new paper picks up, with a manganese twist.

Collagen keeps showing up. A University of Liverpool-led team reported evidence of collagen in an Edmontosaurus hip bone from the Hell Creek Formation, about 66 million years old. They used mass spectrometry and protein sequencing, identified fragments of collagen alpha-1, and detected hydroxyproline. One of the authors argued this undercuts the idea that any organic material in fossils must be contamination.

The pattern. Over about three decades, the evidence for "some original molecules can survive" has gotten stronger. The evidence for "this specific squishy structure is definitely a cell" is still argued case by case. That's exactly where the Brazilian fossil sits.

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Part 5: Why anyone should care

Even if the blobs turn out to be mineral casts, the chemistry has real consequences.

A new kind of paleontology. Bones tell you about size, shape and how an animal moved. Molecules could tell you about how it lived. Heme and hemoglobin are tied to oxygen handling, which connects to metabolism and activity levels. Grice put it as a way to study the evolution of blood and even how active ancient animals were. That's a big "if", but it's the kind of question bones alone can't answer.

Old fossils, new tricks. The Liverpool team suggested that a century's worth of microscope images of fossil bone, taken with polarised light, might contain hints of preserved collagen. Those fossils could now be re-screened for protein work. Imagine going back through museum drawers with new questions.

Looking for life elsewhere. Curtin's Martin Van Kranendonk pointed out that if fragile biological molecules can last more than 100 million years under the right conditions, astrobiologists may need to rethink where and how they search for traces of ancient life, including beyond Earth. This is a long reach, but it follows the logic: learn what preservation looks like on Earth first.

A better method. Doing chemistry in place, tied to specific microscopic structures, is a model other labs can copy. Even skeptics said they like the technical rigour.

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Part 6: How to read a "wow" fossil headline

This is a good case study in how to read science news. A few habits will save you from being fooled in either direction:

1. Separate the claims. "Heme detected" and "red blood cells found" are not the same statement. One can be right while the other is wrong.
2. Ask what the controls are. Here, the comparison between the bone and the surrounding rock is a good one. Always look for the "what if it's contamination?" test.
3. Check who's doubtful, and why. Specific, technical objections (nuclei, size, alternative minerals) carry more weight than vague "I don't buy it" reactions.
4. Watch the verbs. "Resembling", "consistent with", "may" and "suggests" are doing real work in the paper. Headlines tend to drop them.
5. Wait for replication. One lab, one specimen is a starting point. Other labs testing other fossils is what turns a claim into knowledge.

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Part 7: Myths worth killing

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Quick facts

• Age: about 115 million years, roughly 35 million years older than the previous oldest candidate dinosaur blood cells
• Dinosaur size: a juvenile, around 3.1 metres long and about 34 kilograms, according to reports on the specimen
• Structure size: roughly 23 by 20 micrometres, about a third the width of a human hair
• Key mineral: hausmannite, a manganese oxide
• Key molecules: heme B, a degraded heme (3,8-diethyl heme B), and hydroxyproline from collagen
• Where it was published: PNAS, volume 123, issue 46
• Who disagrees: Mary Schweitzer and Evan Saitta question whether the structures are cells, and Maria McNamara asks whether other heme sources were ruled out

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What it all adds up to

Stripped of the hype, here's the honest picture.

A careful team found round, cell-sized structures inside a dinosaur's blood-vessel channels, and they found heme-type chemistry sitting right on them. The chemistry looks convincing to many people. The cell identification is the shaky part, and some of the best researchers in the field have good, specific reasons for doubt.

That doesn't make the work a dud. Even the doubters say they're glad to see molecular methods used on ancient fossils. If the structures are mineral casts that kept a trace of the chemistry, that's still remarkable. And if they're real fossil red blood cells, then the rules about what can survive deep time just got rewritten.

Either way, the lesson is a good one. Fossils aren't just rock. Sometimes they're an archive, and we're only now learning how to read it.

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Sources and further reading

• Grice et al., 2026, PNAS: Heme signatures in mineralized red blood cells within vascular canals of a 115-million-year-old dinosaur bone
• ScienceDaily (Curtin University): Scientists just found dinosaur blood that survived 115 million years
• Live Science: Traces of ancient blood found in 115 million-year-old dinosaur fossil, new study claims
• Indian Defence Review: Scientists detect 115-million-year-old dinosaur blood, but one mystery remains unsolved
• Sci.News: 115-million-year-old dinosaur bones preserve chemical traces of red blood cells
• ScienceAlert: Dinosaur blood cells detected in 115-million-year-old fossil
• ScienceDaily (University of Liverpool): Organic molecules found in 66-million-year-old dinosaur bones