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FROH — the key metric
FROH is the fraction of your autosomal genome covered by ROH >1.5 Mb. Outbred Europeans: ~0.3%. Romani: 5–8%. The higher the FROH, the more your parents share ancestry.
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Length tells you "when"
Long ROH (>10 Mb) = recent ancestor (within 5 generations). Short ROH (1–5 Mb) = ancient founder event. Formula: generations ≈ 50 ÷ length(Mb).
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Population fingerprint
Each isolated population has a characteristic profile — number, length distribution, and total SROH. This tool checks 8 known population signatures from your raw file.
🟢Europeans (outbred)~0.3%
Baseline for non-isolated European populations. Few short ROH, no long segments, SROH typically under 10 Mb.
FROH 0.2–0.5%nROH <10No long ROH
🏔️Basque~1.2%
Pyrenean and linguistic isolation since the Mesolithic. Ancient and moderate endogamy — many short ROH, no long segments. One of the most genetically distinct European populations.
FROH 0.8–2.2%Short ROHAncient isolation
🇫🇮Finnish~1.5%
Strong Neolithic founder effect, reinforced by multiple settlement waves. Many small ROH, allele frequencies very distinct from other Europeans (Finnish disease heritage).
FROH 1.0–3.0%Founder effectShort-medium ROH
🏝️Sardinian~1.8%
Long-standing island isolation and genetic drift. Preserves strong Neolithic Anatolian ancestry. Numerous short-medium ROH reflecting ancient, not recent, isolation.
FROH 1.2–3.5%Island isolationNeolithic ancestry
✡️Ashkenazi Jewish~2.5%
Founder bottleneck ~700 years ago following expulsion from Central Europe (~5,000–10,000 founders). Many medium ROH (5–15 Mb), reflecting ~30 generations back.
FROH 1.8–4.5%~700 years agoMedium ROH
⭐Druze~3.5%
Closed religious community since the 11th century — no outside marriage for ~40 generations. One of the highest FROH values among Middle Eastern populations.
FROH 2.5–6%Since 11th centuryLong ROH
🌾Mennonite / Amish~4.0%
Founded in the 17th–18th century by ~200–500 Anabaptists, followed by strict endogamy. Similar FROH to Ashkenazi but longer ROH — more recent and smaller founding group.
FROH 2.8–8%~300 years agoMedium-long ROH
🏜️Bedouin / Arab isolated~4.5%
Preferential cousin marriage (ibn amm) widespread in Arab tribal societies. Often very recent endogamy (1–4 generations) producing very long ROH. ROH >20 Mb = 2nd/3rd degree relatives.
FROH 3–12%Recent cousin marriageVery long ROH
🪗Romani~5.5–8%
Founder effect from departure from NW India ~1,000 years ago (estimated 200–1,000 founding individuals). Triple signal: high FROH + long ROH (>8 Mb) + South Asian admixture. Must be cross-referenced with your ancestry report.
FROH 3.5–12%~1000 years agoSouth Asian admixtureLong ROH
🕌Palestinian / Arab Muslim~2.0–4%
Levantine population with centuries of preferential cousin marriage in many communities. ROH profile can resemble Druze or Bedouin patterns without sharing those specific origins.
FROH 1.5–6%Cousin marriageMedium-long ROH
🇮🇹South Italian / Sicilian~1.0–2.2%
Rural village isolation in southern Italy (especially Calabria, Sicily, Basilicata, Abruzzo) for centuries. ROH pattern is distinct from Sardinian — less ancient, more regionally fragmented.
FROH 0.8–2.5%Village isolationShort-medium ROH
🇦🇲Armenian~1.5–3%
South Caucasian population with Neolithic continuity and centuries of community endogamy. Mix of ancient short ROH and moderate medium ROH. Distinct allele frequencies from Middle Eastern neighbours.
FROH 1.2–4.5%Caucasian isolateMixed ancient/recent ROH
🌻Hutterite~5–9%
Extreme founder effect — entire modern community descends from ~400 ancestors (18th c.). Among the highest documented FROH in any Western population. Very long, numerous ROH reflecting both founding bottleneck and ongoing endogamy.
FROH 3–10%~400 foundersLong ROH
