Hemoglobin and other blood molecules found preserved in dinosaur fossils

Two iconic dinosaurs – Tyrannosaurus rex and Brachylophosaurus canadensis – have yielded a fresh line of evidence that traces of their original biology can survive for tens of millions of years.

In new work, researchers at North Carolina State University identified hemoglobin – the oxygen-carrying protein in blood – and its iron-bearing heme group in bone extracts from both animals.

The finding strengthens a growing body of data showing that certain biomolecules can persist in exceptional fossils. It also clarifies how they change as fossils form.

Researchers have debated and re-examined soft, stretchy tissues from these same specimens for nearly two decades.

Teams have used high-resolution imaging, antibodies, and protein sequencing to argue that the materials are genuine remnants of dinosaur biology rather than modern contaminants. The latest study adds another tool – and another confirmation.

Light unlocks dinosaur chemistry

The team turned to Resonance Raman (RR) spectroscopy. In this method, laser light is tuned to a molecule’s electronic transitions. This causes only that molecule to “sing” back with a strong signal.

“Raman spectroscopy essentially uses light waves to identify a molecule’s energetic ‘fingerprint,’” said physicist Hans Hallen, the study’s corresponding author.

“Resonance Raman, which we use here, takes that process one step further by using light already tuned to the molecule of interest – so only that type of molecule will resonate.”

That resonance dramatically boosts the signal from specific bonds – crucial when your targets are rare, damaged molecules embedded in a complex fossil matrix.

“This strong signal allows us to find the needle (hemoglobin remnants) in the haystack (messy fossil) to see how this molecule has changed from the functional living state, revealing the chemical changes molecules undergo in deep time,” Hallen added.

RR spectra from T. rex and Brachylophosaurus extracts showed signatures consistent with heme still bound to globin proteins. In addition, they indicated heme bound to goethite, an iron oxide mineral linked to oxidized iron.

The researchers cross-checked those signals against demineralized modern ostrich bone and human blood to anchor their interpretations.

Blood molecules traced to dinosaurs

Because Raman detects bonds rather than whole molecules, skeptics often point out that generic signals could arise from modern microbes or other contaminants.

That’s where the extra selectivity of RR – and the structural information in the spectra – matters.

“RR identifies both bonds and structure,” said paleobiologist Mary Schweitzer, a co-author on the work.

“We know that heme is there and that it is still bound to hemoglobin protein – contaminants like bacteria don’t have those specific bonds, so we can say that the molecules are from the animal, or in this case, the dinosaur,”

The team also mapped how those spectral fingerprints shift as hemoglobin decays. After death, the protein breaks down, damaging the heme ring and oxidizing the iron inside it.

RR data show that goethite forms on that iron, and the heme can bind to the mineral surface.

Tellingly, the researchers observed the early stages of the same degradation pathway in modern samples, suggesting that key steps happen relatively quickly and then stabilize.

Dinosaur blood survived fossilization

Beyond confirming what the molecules are, the spectral changes reveal a plausible route for how they survived.

Goethite is a bio-related mineral – it often forms in association with biological activity – and the new data hint that it doesn’t just grow near proteins; it can latch onto and stabilize fragments. “We didn’t know that it could bind to and stabilize protein fragments,” Hallen said.

That matters because it shows a mechanism that locks delicate organics in place and protects them during fossilization.

Researchers already know that heme persists in sediments far older than the age of dinosaurs, but the path from fresh blood to ancient rock has remained murky.

Pinning down the chemistry helps explain why hemoglobin, in particular, shows up as a survivor – and why some fossils preserve molecular vestiges while others do not.

A new view of fossil preservation

The study reinforces a shift in paleontology: under the right conditions, original biochemistry can endure deep time, and modern tools can detect and interpret it.

Instead of a binary “preserved or not,” researchers are piecing together degradation pathways, mineral partnerships, and microenvironments that favor survival.

For dinosaur biology, that means more than just curiosity. Hemoglobin and heme in blood play key roles in metabolism, oxygen transport, and overall physiology.

Their presence, and the way they degrade, defines how tissues fossilize and what information we can still extract.

Blood chemistry spans eons

For dinosaur fossil science, mineral–organic interactions like heme–goethite may help preserve blood proteins and molecular fragments throughout Earth’s history.

“Heme has been identified in sediments that are much, much older than dinosaurs, so we know that it persists,” Schweitzer noted.

“Understanding why hemoglobin preserves, and the role that heme plays in the process, is really important if we want to know how these ancient molecules survive through time.”

The upshot is both practical and provocative. Resonance Raman pinpoints specific ancient molecules within messy fossils, and the chemistry it reveals also serves as a preservation roadmap.

That’s a powerful combination for anyone trying to read life’s oldest diaries written in stone.

The study is published in the Proceedings of the Royal Society A Mathematical Physical and Engineering Sciences.

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