Naturally preserved, not mummified. At Chemical and Engineering News, Prachi Patel offers a look at the most interesting findings for 2024, including “Cryptic brain preservation”:

Brains usually dissolve within days after death. Depending on environmental conditions, though, five processes can preserve brains for hundreds or even thousands of years, researchers concluded after analyzing records of over 4,400 brain fossils (Proc. R. Soc. B 2024, DOI: 10.1098/rspb.2023.2606). Freezing, tanning, dehydrating, and saponifying all do the trick. A fifth, cryptic, method preserved brains for as long as 12,000 years.

“Fascinating findings of 2024,” December 17, 2024

That counters our usual assumption that brains don’t get preserved. The end-of-year squib links to an article last March by Carolyn Wilke:

Morton-Hayward and her colleagues searched 400 years of literature for archaeological reports of discolored, shrunken brains. They paired records of 4,405 brains from 213 sources with information about the conditions the specimens were exposed to, including climatic data such as temperature and precipitation. This revealed trends about five mechanisms by which brains can be preserved for hundreds and sometimes thousands of years.

Frozen brainshad the shortest longevity, with most enduring less than 500 years. In temperate peat bogs, brains were found preserved for up to 2,800 years. The mechanism at work there is tanning, which occurs when compounds from sphagnum moss react with free amino groups in decaying tissue. Dehydrated brains, mostly discovered in sweltering deserts, persisted for up to 5,200 years. Some brains in the literature were identified as saponified, a process that transforms triglycerides, a group of fats, into a smelly substance known as grave wax.

“Why some human brains don’t break down” after thousands of years,” March 28, 2024

But the research team also found a little-known fifth process that preserved brains for up to 12000 years. From their open access paper:

It is unclear what accounts for the unknown mechanism of preservation, in which the human brain persists on longer geological time scales (≳12 000 y; versus the maximum age of dehydrated: 8970 y, frozen: 5180 y, saponified: 3900 y and tanned: 2790 y), after other organs have perished. The skull might afford the brain protection from exogenous agents of degradation (e.g. animal scavenging, humidity/aridity, soil pH, etc.), akin to bone marrow shielded within the medullary cavity, the decomposition of which is inhibited where cortical integrity is maintained [37]. However, preserved brains have been discovered in skulls fragmented by both perimortem trauma [38] and taphonomic damage [39]. The persistence of the brain in this unknown type of preservation, irrespective of any protective action of the skull and in varied depositional settings, suggests some intrinsic quality associated with nervous tissue itself that permits long-term preservation.

Morton-Hayward Alexandra L., Anderson Ross P., Saupe Erin E., Larson Greger and Cosmidis Julie G. 2024 Human brains preserve in diverse environments for at least 12 000 years Proc. R. Soc. B.29120232606 http://doi.org/10.1098/rspb.2023.2606

It’s not Jurassic Park but could help researchers solve some ancient human history puzzles down the road.