Jurassic Beer: Which Ancient Organic Materials Survive?

At a summer internship for undergraduates interested in natural history (read: nerd camp!), I spent 10 weeks debating which scientific discipline boasted the highest rate of alcohol consumption at annual conferences. Ichthyologists, naturally, drink like fish, and from personal experience, I know anthropologists can party like it’s the Pleistocene. But if dedication to the beverage earns any points, Dr. Raul Cano of Cal Poly, San Louis Obispo has won the award for paleontologists as a discipline. He succeeded in fermenting beer using 45-million-year old yeast and has partnered with local brewers to create Fossil Fuels Brewing Company, which will begin selling the brew in Northern California. Now, this is a feat verging on miraculous, as the organism really (really!) should have been killed off by the fossilization process. But it also brings up questions of what exactly fossilization is, what we thought it did twenty years ago, and what we now are beginning to realize can survive the process.

Recent news reported that the amazing finding of preserved blood vessels and other soft tissue in fossilized dinosaur bones first reported in 2005 was independently confirmed by another lab. The 68 million-year-old collagen molecules are remarkably similar to those found in modern-day chickens. The claim of un-fossilized material dating to the Cretaceous Epoch ran so counter to accepted knowledge about the fossilization process when it was first announced that many scientists dismissed the report out of hand. In the past four years, however, it has become clear that soft tissue preservation is more widespread than anyone imagined – the problem is just that no one really ever looked for it before!

Bone is made of both organic and inorganic material. The inorganic mineral hydroxyapatite gives bone its strength and rigidity. The organic material, containing proteins such as collagen, provides that stiff skeleton some flexibility, preventing bones from shattering with each movement. The fossilization process is simply the transformation of the organic part of bone into rock (inorganic material). Muscles and organs rarely fossilize because they have so little inorganic material to start with. Bones are easier to fossilize, given that they start already 70% mineralized. Teeth, made of enamel and dentin with very little collagen, are already 95% mineralized, so are the most frequently preserved elements in the fossil record.

Conventional understanding of fossilization held that unless the organic material in bone rapidly turned into rock, it would decay. “Very old” preserved soft-tissue before 2005 had been found in Ice Age megafauna like mammoths, dating back 50,000 years. This material was preserved because it was buried in ice, slowing the decay process. “Subfossil” material such as giant lemurs from Madagascar and the “hobbit” species from Indonesia retains soft tissue because it dates to younger than 20,000 years ago and has not yet had time to fully mineralize. The Tyrannosaurus rex fossil excavated in 2003 was dated to 68 million years ago and was not preserved in ice. However, after one of the femora was broken during transportation, the internal contents were visible. The lab examining the material then took the unorthodox step of dissolving the mineralized part of the bone with a weak acid. I’m confused by this step, since if the fossil were truly entirely mineralized as everyone expected, it would have entirely disappeared. And who does that to T. rex fossils? But in this case, some soft tissue remained after the mineralized portion was removed. And it is from this that the genetic signal of the collagen protein was found to resemble modern-day chickens, initially in 2007 and confirmed last week.

This analysis is not one that a paleoanthropologist would readily perform. Dinosaur fossils, while millions of years older than any human fossil, are far more plentiful. Perhaps as many as 700 species of dinosaur existed during their 160 million year reign, and many of those species lived in fossilization-promoting environments. Even the most species-friendly anthropologists (who belong to a group called the “splitters” due to their fondness for naming multiple species) only designates ~20 hominin fossil species, spanning only the past seven million years. Our ancestors also had the annoying habit of living in tropical rainforests and along ancient coastlines, assuring their remains would be lost to modern scientists forever. The abundance of dinosaur fossils perhaps explains why one brave researcher undertook such a potentially destructive experiment – even if one fossil was dissolved completely, there were plenty of others around. This unorthodox experiment paid off, however, and will hopefully inspire similar investigation in other fossils. After all, if 45-million-year-old yeast can still be brewed into beer, and T. rex proteins can be sequenced after 68 million years, we’re two steps closer to Jurassic Park becoming a reality – but with drunk dinosaurs.

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