HRLC-MS/MS Reveals Why Ancient Brains Preserve

Brains normally rot quickly after death, yet, oddly, they are sometimes the only soft tissue found preserved in ancient burials, even in over 1300 cases where wet, low-oxygen graves left everything else reduced to bone. To figure out why, a team of researchers buried mouse carcasses for six months in four different burial setups that varied in moisture and oxygen levels. They analyzed the brain's proteins at six different points in time using advanced laboratory techniques, including characterizing the brain proteome by high-resolution liquid chromatography-tandem mass spectrometry (HRLC-MS/MS), then tracked how more than 1.26 million individual protein fragments broke down (or didn't) to identify which ones tend to disappear quickly and which ones tend to remain. A paper based on this research was published in the Journal of Proteome Research.¹

Why Do Brains Sometimes Survive Alone, with No Other Soft Tissue, in Wet, Low-Oxygen Graves?
 
More than 4400 human brains have been found at burial sites dating back as far as 12,000 years. Often, it's easy to explain why: freezing, drying out, tanning (like natural mummification), or turning into a soap-like substance can preserve several organs at once, so when a brain survives this way, other soft tissues usually survive alongside it. But surprisingly, almost a third of these ancient brains don't fit any known explanation. They show up as a tough, shrunken lump that somehow survived completely on its own, with no other soft tissue left, mostly in waterlogged, low-oxygen burial spots.²

What Does That Mean for How We Interpret the Proteins Found in These Graves?

Preserved ancient brains hold more surviving old proteins than almost anything else within cadavers, and doctors and scientists already routinely study proteins in dead brain tissue for both criminal investigations and disease research. In these fields, what remains of the proteins later in decomposition is increasingly seen as meaningful data. The common assumption is that once the first stage of decay (where a tissue's own enzymes start digesting it) is over, the proteins that remain mostly reflect what was going on biologically before death, not chemical changes happening after death. But the fact that brains specifically tend to survive in wet, low-oxygen burial spots pushes back on that assumption. It suggests that the conditions a body is buried in can actively change which molecules survive, and in doing so, shape what we're examining when we study "ancient" proteins.^1,3-6

What Explains Brain Preservation in Wet, Low-Oxygen Graves, and Is the Finding Reliable?

The researchers found that oxygen turned out to be the biggest factor in what survived after the burial process. When bodies were buried with more air exposure, most proteins broke down and disappeared. But in wet, low-oxygen conditions, a specific set of tougher protein pieces remained. These surviving pieces tended to have a more stable, organized structure, contained parts that interact with metals and fats, and showed signs of being chemically welded together by oxidation rather than torn apart by it.¹

“By linking intrinsic tissue chemistry and environmental context,” write the authors of the paper,¹ “our results move brain preservation from anomaly to expectation: resolving why brains outlast other soft tissues in waterlogged, oxygen-poor burials, and revealing that the molecular signatures of post-mortem peptide persistence closely mirror those of pathological protein stabilization in brain aging and neurodegeneration.”

The researchers flag two study limitations. First, they froze carcasses before burial, which never happens naturally, but since every sample was frozen identically, comparisons between groups remain fair — it just makes the setup less realistic. Second, they controlled oxygen exposure through air access but didn't measure actual oxygen levels during decay. Since bodies can rapidly deplete nearby oxygen, even "oxygen-rich" setups may have turned low-oxygen quickly. Rather than undermining their conclusions, the researchers state that this supports their theory: preservation depends on how long oxidative breakdown occurs before oxygen runs out, with slower depletion in open setups causing more protein damage.¹

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References

1. Morton-Hayward, A.; Flannery, S.; Berry, P. et al. Molecular Solution to the Paradox of Ancient Brain Preservation. J Proteome Res. 2026.DOI: 10.1021/acs.jproteome.6c00200
2. Morton-Hayward, A. L.; Anderson, R. P.; Saupe, E. E. et al. Human Brains Preserve in Diverse Environments for at Least 12 000 Years. Proc Biol Sci. 2024, 291 (2019), 20232606. DOI: 10.1098/rspb.2023.2606
3. Morton-Hayward, A.; Flannery, S.; Vendrell, I. et al. Deep Palaeoproteomic Profiling of Archaeological Human Brains. PLoS One 2025, 20 (5), e0324246. DOI: 10.1371/journal.pone.0324246
4. MacKenzie, J. M. Examining the Decomposed Brain. Am J Forensic Med Pathol. 2014, 35 (4), 265-270. DOI: 10.1097/PAF.0000000000000111
5. Krassner, M. M.; Kauffman, J.; Sowa, A. et al. Postmortem Changes in Brain Cell Structure: A Review. Free Neuropathol. 2023, 4, 10. DOI: 10.17879/freeneuropathology-2023-4790