How We KnowAnswer
Mutation by Natural Dominance: One Mutation or a Hundred?
If 100 bacteria carry the same DNA change, did it arise once or many times? The answer matters when testing Ricardo Maldonado’s hypothesis.
THE QUESTION LIBRARY HOW WE KNOW
Why Can We Read Mammoth DNA but Not Dinosaur DNA?
A frozen mammoth tooth can hold readable DNA. A dinosaur fossil can preserve the shape of a bone for far longer. Here’s why those are different feats.
THE SHORT ANSWER
Cold ground can slow DNA’s breakdown enough for short fragments to survive. Researchers read DNA from Siberian mammoth teeth more than a million years old. The last non-avian dinosaurs lived about 66 million years ago, and no DNA sequence from one has been reliably confirmed. A fossil can preserve the shape of a bone long after the genetic information inside it is gone.
- Cold conditions slowed DNA damage in Siberian mammoth teeth.
- Fossil shape and DNA sequence preserve different kinds of evidence.
- No DNA sequence from a non-avian dinosaur has been reliably confirmed.
About this picture
Original AI-generated illustration for God Plays Dice. It pairs a mammoth molar in frozen ground with a fossilized bone in rock. Neither side depicts an actual specimen.
WHERE THE EVIDENCE STANDS
How sure are we?
- Researchers recovered DNA from Siberian mammoths more than a million years old.The 2021 study read short fragments from three molars; two were more than a million years old.
- Mineralized structures in the Aratasaurus bone preserve the shapes of original red blood cells.The 2026 study proposes this interpretation from microscopy and heme-related chemistry. It did not report a dinosaur DNA sequence.
- A DNA sequence from an extinct non-avian dinosaur has been reliably confirmed.No such sequence has been authenticated.
WHAT WE DON’T KNOW YET
There is no universal age limit for readable DNA. Conditions, fragment length and the ability to rule out contamination all matter.
WHAT WOULD CHANGE THIS ANSWER
Independent laboratories recovering authentic, identifiable DNA from a securely dated non-avian dinosaur specimen would change the evidence.
A mammoth tooth can hold readable genetic letters after a million years. A dinosaur fossil can preserve the shape of a bone for tens of millions of years, long after its DNA has broken down. That’s because keeping a shape and keeping a sequence are two different things.
THE LONG ANSWER
THE LONG ANSWER · ABOUT 3 MINUTES
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Keep asking
How do scientists know how old rocks and fossils are?
Scientists combine the order of rock layers with natural atomic clocks that measure time in years.
New here?
God Plays Dice answers big questions in plain words, with sources and one of six honest labels.
Words worth knowing (3)
- Permafrost
- Ground that stays at or below freezing for at least two consecutive years.
- Genome
- An organism’s full set of genetic instructions.
- Environmental DNA
- Genetic material shed by organisms and recovered from their surroundings, such as sediment or water.
Sources & further reading
(3) · Checked Nov 5, 2026
- Million-year-old DNA sheds light on the genomic history of mammoths ↗Nature · University of East Anglia repositoryOriginal research on DNA recovered from Siberian mammoth molars.
- The half-life of DNA in bone: measuring decay kinetics in 158 dated fossils ↗Proceedings of the Royal Society B · PubMed CentralA measured estimate for one DNA stretch in a specific set of moa bones.
- A 2-million-year-old ecosystem in Greenland uncovered by environmental DNA ↗Nature · University of Cambridge repositoryOriginal research on fragments from an ancient ecosystem preserved in sediment.
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