Age dating dinosaur bones
Half the DNA in a fossil disappears roughly every 500 years and DNA should become unreadable in 1.5m years. The oldest date to 4m years ago, but the peptide bonds holding a protein’s amino acids together also degrade over time, so it’s unclear if they could survive in 75m year old dinosaur fossils.
Meanwhile, living things – bacteria, protists, fungi, plant roots and nematodes – thrive underground.
Bones, unlike rock, have open spaces for marrow, blood vessels and cells, which now create space for microbes, and carry water and nutrients.
Bone also contains phosphorus needed to make DNA and cell membranes.
Most remarkably, there is the deep biosphere, a vast, subterranean microbial ecosystem starting under our feet and extending into rock kilometres underground. If it does, that creates problems for identifying the original biological material of fossils.
Ancient amino acids show a 1:1 ratio, but the bones were dominated by left-handed molecules, showing recent biological activity. Living things take carbon from atmospheric CO₂, which contains radioactive carbon-14.
Carbon-14 undergoes radioactive decay, with half its atoms disappearing roughly every 6,000 years.
No detectable carbon-14 should survive from 76m years ago, but the bones were full of it.
Either these dinosaurs died a few thousand years ago, or they were contaminated by living things.
Moreover, organic tissues and vessel-like structures extracted from the bones – similar to those identified elsewhere as dinosaur tissues – glow like a Christmas tree when stained with a flourescent dye that binds to DNA.