Genetic Genealogy Hypothesis Engine

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Genetic Genealogy Hypothesis Engine

Build, compare, test, and document competing explanations in a DNA genealogy case.

ℹ How this works

The Genetic Genealogy Hypothesis Engine helps you investigate a difficult genealogy question by comparing competing explanations against the evidence you have collected.

Instead of asking only “Does this DNA match fit my theory?”, the engine asks: “Which explanation is currently best supported, what evidence contradicts it, and what should I investigate next?”

1
Define the question Start with a specific research question, such as: “Is John Smith my biological grandfather?”
2
Create competing hypotheses Record the main explanation and plausible alternatives instead of testing only one theory.
3
Add your evidence Record DNA matches, segments, triangulation, genealogy, historical records, contextual evidence and contradictions.
4
Evaluate the evidence Consider strength, quality, corroboration, independence and DNA compatibility where applicable.
5
Compare the hypotheses The engine produces an Evidence Support Index showing which explanation currently has the strongest support.
6
Find the next best evidence Look for evidence that can distinguish between competing explanations rather than simply adding more of the same evidence.
7
Document the case Generate a case report and export the research data so your reasoning can be preserved.
!
Evidence is not certainty The engine does not calculate biological probability. Its score is a structured comparison aid.
Why this matters: DNA alone may fit several possible relationships or family paths. A strong genetic genealogy case combines DNA evidence with genealogical research, documentary evidence and active consideration of alternative explanations.
Step 1

What are you trying to establish?

Genetic genealogy cases often involve several explanations that can fit the same DNA evidence. This engine helps you record those explanations, attach evidence to them, identify contradictions, and compare the current level of support.

Important: The Evidence Support Index is a structured research heuristic. It is not a probability, likelihood ratio, or scientific determination of biological relatedness.
Step 2

Case Setup

Define the research question and record circumstances that may affect how DNA evidence should be interpreted.

Potential interpretation complications

Select any conditions that could make apparently strong evidence less independent or harder to interpret.

Step 3

Competing Hypotheses

Add the explanations you want to compare. A strong research process should normally include the main hypothesis and at least one plausible alternative.

Add a hypothesis

Step 4

Evidence

Add evidence one item at a time. Evidence can support a hypothesis, contradict it, or provide neutral contextual information.

Add Evidence

Used only as a rough compatibility signal.
Step 5

Case Analysis

The engine combines evidence strength, quality, corroboration, independence, evidence type, and case complexity. Scores are comparative support indices — not probabilities.

Step 6

Next Best Evidence

The most useful next step is not necessarily "more DNA". The goal is to find evidence that can distinguish between the competing explanations.

Step 7

Case Report

Generate a concise research record that can be saved, printed, or shared with another researcher.

Research note: This tool is designed for evidence organization and hypothesis comparison. Shared-cM ranges are guides rather than hard boundaries, and correlated evidence should not be treated as independent. DNA evidence should be interpreted alongside triangulation, family trees, documentary research, and the possibility of pedigree collapse, endogamy, adoption, or non-paternity events.

DNA Academy - Quick Answers

Simply enter the total centimorgan (cM) value you share with a match (e.g., 876 cM). Our calculator gives you an immediate probability list of relationships. For 876 cM, it might show 60% chance of grandparent, 30% of half-aunt/uncle, etc. This removes the guesswork when you see unfamiliar names in your match list.

Matches over 20 cM are generally considered genealogically useful. Matches under 10 cM are often “identical by chance” (IBC) and not from a recent ancestor. According to the ISOGG, we recommend focusing on matches > 50 cM for building your tree, as these are almost always valid. Test our calculator to see the probabilities.

A segment is a continuous stretch of DNA on a specific chromosome. Your total cM is the sum of all segments you share with a match. For example, you might share 120 cM spread across 4 segments (each on different chromosomes). Our calculator uses the total cM to determine relationship probabilities.

Yes! Our calculator includes half-relationships in its probability list. For example, 1,700 cM might show a 50% chance of grandparent and a 30% chance of half-sibling. The tool uses the latest Shared cM Project data to give you the most accurate probabilities, including half-aunt/uncle and half-first-cousin options. Try our calculator yourself.

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