How We KnowAnswer
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 QUESTION LIBRARY HOW WE KNOW
How much evidence should it take to change your mind?
How to change your confidence with evidence, understand Bayesian thinking, and use Occam’s razor without assuming the simplest story must be true.
THE SHORT ANSWER
There is no fixed amount. Change your confidence when evidence favors one explanation over its alternatives. A clue may justify a small shift; a strong test may justify a larger one. Bayesian thinking helps you make that comparison. Occam’s razor discourages unnecessary assumptions, but cannot guarantee the simplest answer is right.
- Confidence can change gradually.
- Compare evidence under competing explanations.
- Simplicity cannot replace a good fit to observations.
WHAT WE DON’T KNOW YET
There is no agreed starting probability or decision threshold for every everyday claim. Missing alternatives, uncertain observations and assumptions can change the conclusion.
WHAT WOULD CHANGE THIS ANSWER
For a particular belief, a checked observation that fits a competing explanation better, or a failed assumption behind the earlier judgment, would justify revision.
Changing your mind need not mean jumping from “definitely true” to “definitely false.” You can become less certain, prefer a different explanation, or say that you do not know yet. A useful question is: what would I expect to find if this claim were wrong?
Imagine your phone will not charge. A faulty cable and a damaged phone are two possibilities. If it charges with another cable but repeatedly fails with the original under the same conditions, the cable explanation gains support. One failed attempt alone tells you less.
THE LONG ANSWER
THE LONG ANSWER · ABOUT 2 MINUTES
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Keep asking
Why Can We Read Mammoth DNA but Not Dinosaur DNA?
Cold ground can slow DNA’s breakdown enough for short fragments to survive.
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God Plays Dice answers big questions in plain words, with sources and one of six honest labels.
Words worth knowing (2)
- Prior
- A starting probability before considering new evidence.
- Bayesian updating
- Revising probabilities in light of evidence.
Sources & further reading
(3) · Checked Oct 5, 2026
- Bayes’ Theorem ↗Stanford Encyclopedia of PhilosophyOfficial scholarly reference; sections 1–3 support the prior/evidence comparison. Checked October 5, 2026.
- Simplicity ↗Stanford Encyclopedia of PhilosophyOfficial scholarly reference; sections 1–2 and 5 distinguish simplicity from evidential fit and discuss its disputed justification. Checked October 5, 2026.
- Bayesian Epistemology ↗Stanford Encyclopedia of PhilosophyOfficial scholarly reference; sections 1.5,1.8–1.9 explain prior choice, updating disputes and idealization. Checked October 5, 2026.
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CONTINUE THE THREAD
Where this question leads.
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.
How We KnowAnswer
Are the colors in space photos real?
A space image can be faithful to measured light without matching human eyesight. Here is how to read the translation.