The evolution of the futhark: one source row of 24 runes — two diverging developments (Elder → Younger Futhark 24→16; Elder → Anglo-Saxon futhorc 24→29+)

⚠️ Honesty frame (read first)

This is a summary of the navigational open sources (Wikipedia: "Younger Futhark", "Anglo-Saxon runes", "Runes", "Old English rune poem"). Wikipedia is navigation, not a primary source. All datings, phonetic values, and attributions to specific scholars are flagged and are subject to verification against the primary runological literature (Düwel, Page, Antonsen, Spurkland, Looijenga, and others). Where the source does not confirm or the question is disputed — [unverified]. The rune names in the tables are the late attested rows (the Younger Futhark, the Anglo-Saxon futhorc), NOT the proto-forms of the Elder Futhark (those are reconstructions, see names & reconstruction of the 24 runes).

Summary

The source common-Germanic row is the Elder Futhark, 24 runes (three ættir of 8), taking shape around the 2nd–3rd c. and in use down to the 8th c. From it two independent developments diverge, answering the different phonological tasks of different languages and regions:

1. Scandinavia → Younger Futhark (24 → 16 runes), ~8th–11th c. (with the transition of Proto-Germanic / Proto-Norse into Old Norse). The row shrinks.
2. England / Frisia → Anglo-Saxon futhorc (24 → 28–29, in the Northumbrian form up to 33–34 runes), ~5th–11th c. The row expands to fit the phonology of Old English and Old Frisian.

These are two diverging, not sequential stages: neither "descends from" the other; both are independent descendants of a single 24-rune ancestor. This is precisely why the rune poems reflect these late rows rather than the Elder Futhark directly: the Anglo-Saxon poem (29 stanzas) is the futhorc; the Norwegian and Icelandic poems are the Younger Futhark (16 runes). See the rune poems (Dickins 1915).

The term itself records this divergence: futhark (Elder, by the 1st and 4th runes: f-u-þ-a-r-k) / futhorc (Anglo-Saxon: f-u-þ-o-r-c, the 4th rune shifting ansuz → ōs, /a/ → /o/) / futhork (Younger).

Elder → Younger Futhark (24→16)

When / where / why. The reduction completes by the end of the 8th c. in Scandinavia, on the threshold of the Viking Age, and correlates with the transition of Proto-Norse into Old Norse. The language transition is dated roughly from the 5th c.; the shrinking of the row — the 8th c.; between them several centuries of gradual evolution.

The paradox: there came to be MORE phonemes, but FEWER runes

The key and counterintuitive fact:

• historical-fact The shrinking of the row (24 → 16) happened simultaneously with phonetic changes that increased the number of distinguishable phonemes in spoken language (Proto-Norse → Old Norse). — Wikipedia "Younger Futhark".
• historical-fact The chief change: the distinction of voiced and voiceless consonants ceased to be expressed in writing. One rune came to cover both members of the pair (and often more). — Wikipedia "Younger Futhark".

That is, writing went against phonology: the language was splitting sounds while the row was merging them. The Younger Futhark is a heavily underspecified (phonemically incomplete) system: reading relied on context. This is a direct argument against the notion of runes as an exact "phonetic" record.

How one rune came to denote several sounds

A summary table of the mergers (per Wikipedia "Younger Futhark"; the specific signs are the long-branch forms).

• historical-fact By ætt, the runes lost are: in the 1st ætt — g and w; in the 2nd — æ (ï/eihwaz) and p; in the 3rd — e, ŋ, o, d; the rune j is kept, but with a new sound value. — Wikipedia "Younger Futhark".
• historical-fact The scribal custom avoided carving the same rune twice in a row for one sound; because of this the distinction of long and short vowels was lost in writing. — Wikipedia "Younger Futhark".

Graphic variants (when and why)

The same 16-rune set existed in three writing traditions:

• Long-branch (Danish / "normal"). historical-fact Used above all for monumental inscriptions on stone; full verticals with long branches. — Wikipedia.
• Short-twig (Swedish-Norwegian). historical-fact Nine runes are simplified variants of the long-branch ones; the remaining seven coincide in form. They were in everyday use for private and business messages (often on wood). — Wikipedia.
• Staveless / Hälsinge. historical-fact 10th–12th c.; a further simplification of the Swedish-Norwegian short-twig runes, discarding part of the strokes (including the main staves). They cover the same set of signs as the other Younger Futhark rows. — Wikipedia. [unverified]

Important: these are graphic variants of one row, not different alphabets and not different sound systems. The choice of variant was determined by medium and function (stone-monument vs. wood-everyday), not by language.

The 16 names of the Younger Futhark

The names (per Wikipedia "Younger Futhark"; the meanings are brief glosses, cf. the Norwegian/Icelandic rune poems in the rune poems (Dickins 1915), where the meanings diverge semantically between poems):

fé (wealth) · úr (drizzle/dross — diverges) · þurs (giant) · áss (god) · reið (riding) · kaun (sore/ulcer) · hagall (hail) · nauðr (need) · íss (ice) · ár (harvest/good year) · sól (sun) · Týr (the god Týr) · bjǫrk (birch) · maðr (man) · lǫgr (water) · ýr (yew).

Elder → Anglo-Saxon futhorc (24→29+)

When / where / why. The development is in England and Frisia, ~5th–11th c. Here the row goes in the opposite direction: it expands to fit the changed phonology of Old English / Old Frisian (the Anglo-Frisian group). 24 runes → ~28 in the early form → 29 (the count reflected in the Anglo-Saxon rune poem) → up to 33–34 in the Northumbrian (late) form.

• historical-fact The main phonological driver of the early additions is the Ingvaeonic splitting of the allophones of long and short a: a single rune ansuz ceased to cover the diverged vowels, and separate signs were needed. — Wikipedia "Anglo-Saxon runes".
• historical-fact Part of the later additions are explained as signs for diphthongs characteristic specifically of Old English. — Wikipedia "Runes".

The splitting of *ansuz and the shift of the 4th rune

The most graphic change is the threefold split of the old rune ansuz (ᚨ, /a/, "(pagan) god"):

• historical-fact The early futhorc nearly coincided with the Elder Futhark, except for the split of ᚨ a into three variants: ᚪ āc, ᚫ æsc, and ᚩ ōs. — Wikipedia "Anglo-Saxon runes".
• It is precisely the shift of the 4th rune ansuz (/a/) → ōs (/o/) that gave the row its name: fuþ-o-rc (and not fuþ-a-rk).

The added runes (names and sounds)

The early Anglo-Frisian additions (sound values per Wikipedia "Anglo-Saxon runes",):

The Northumbrian (late) additions —, the meanings of the names partly unknown:

• historical-fact The Anglo-Saxon rune poem counts 29 stanzas (one rune per stanza). — Wikipedia "Old English rune poem". See the rune poems (Dickins 1915).
• historical-fact cweorð, calc, stān, gār are NOT treated in the poem itself — they are present only in the apparatus of Hickes's publication (1705) (at the bottom of the column / on a separate copper plate) and were "hardly in the original of the Cotton manuscript." That is, the Northumbrian runes are a later layer, not part of the 29-rune poem row. — Wikipedia "Old English rune poem".

How some of the old runes changed sound / name

• historical-fact kaunan → ᚳ cen ("torch"): the rune changed both its sound and its name / association. — Wikipedia. (cf. the competing reconstruction kaunan vs. *kenaz in names & reconstruction of the 24 runes, no. 6).
• historical-fact The j-rune (*jēran): in the futhorc it appears in two forms — ᛄ ger and ᛡ īor, both for /j/, with different shapes/names (regional variation). — Wikipedia.
• historical-fact The h-rune: the double-barred ᚻ hægl (continental) is first attested late — 698, on St Cuthbert's coffin; before that — the single-barred variant. — Wikipedia.
• historical-fact The 4th rune: ansuz (/a/, "god") → ōs* ("mouth/speech"), /o/ — a reinterpretation of both the name and the sound (see the split above). — Wikipedia.

Links

• the rune poems (Dickins 1915) — the primary texts of both late rows: the Anglo-Saxon poem (29 futhorc runes) + the Norwegian and Icelandic ones (16 Younger Futhark runes). It is these poems, not the Elder Futhark, that give the attested names; they are the entry point for the reconstruction of the proto-forms. The divergence of meanings between the Norwegian and Icelandic poems (Óss "estuary" vs. "Odin"; Ýr "yew" vs. "bow") is a consequence of the late, divergent development.
• names & reconstruction of the 24 runes — the source 24-rune row and its reconstructed names; the node from which both branches diverge. The disputed runes of the Elder row (no. 6 kaunan/kenaz, no. 13 ī(h)waz, no. 15 algiz) are clarified precisely through comparison with what became of them in the futhorc and the Younger Futhark.