Hence
Episode 001 · sources · Hence Paper

Why are Africa's borders so straight?

Every factual claim in the episode, in the order it is spoken, with the source behind it. Where a number is our own measurement or a source was taken from a standard reference without re-checking, it says so. The episode exists in a short cut (about 41 seconds) and a longer cut (about 62 seconds) that adds three beats.

Last updated: 4 October 2026 · Narration: AI voice · Research and script: human

Claims in the short cut

  1. In 1884, 14 powers met in Berlin.

    Fact
    The Berlin Conference ran from 15 November 1884 to 26 February 1885 with 14 participating states: Austria-Hungary, Belgium, Denmark, France, Germany, Italy, the Netherlands, the Ottoman Empire, Portugal, Russia, Spain, Sweden-Norway, the United Kingdom and the United States.
    Note
    The script says “14 powers”, not “14 European powers”, because the USA and the Ottoman Empire took part.
    Source
    EBSCO Research Starters, “Berlin Conference and the Partition of Africa”, ebsco.com/research-starters/history/berlin-conference-and-partition-africa

  2. Not one African was there.

    Fact
    No African representatives took part in the conference (on screen: “0 African delegates”).
    Source
    Same as above.

  3. They set the rules for carving up Africa.

    Fact
    The conference set rules for claims; its General Act was signed on 26 February 1885. Most straight lines were fixed afterwards, in bilateral European treaties.
    Source
    Same as above.

  4. Treaties from 1885 to 1914 fixed the lines.

    On screen
    Treaty-year markers on the map, as a timeline runs from 1885 to 1914.
    1885
    Lower Congo: Convention between France and the International Association of the Congo, 5 February 1885 (also Portugal and the Association, 14 February 1885). Source: Encyclopaedia Britannica, 11th edition (1911), “Congo Free State”.
    1890
    Namibia–Botswana: Anglo-German Agreement of 1 July 1890. Source: International Court of Justice, Kasikili/Sedudu Island (Botswana/Namibia), judgment of 13 December 1999, icj-cij.org/node/103865
    1891
    Mozambique–Zimbabwe: Anglo-Portuguese Treaty of Lisbon, 11 June 1891. Source: standard reference, not re-verified
    1898
    Nigeria–Niger: Anglo-French (Niger) Convention, Paris, 14 June 1898. Source: en.wikipedia.org/wiki/Anglo-French_Convention_of_1898
    1899
    Egypt–Sudan: Anglo-Egyptian Condominium Agreement, 19 January 1899 (see the 22nd parallel below). The Anglo-French Declaration, London, 1899, is cited from standard references, not re-verified
    1905
    Algeria–Mali/Niger: the boundary between Algeria and French West Africa was agreed on 7 June 1905 and further defined by the Niamey Convention of June 1909. These were internal French colonial lines, not an international treaty, hence the on-screen label “French colonial lines 1905–09”. Sources: en.wikipedia.org/wiki/Algeria–Mali_border, en.wikipedia.org/wiki/Algeria–Niger_border

  5. Egypt and Sudan? The 22nd parallel.

    Fact
    Under the Anglo-Egyptian Condominium Agreement of 19 January 1899, Sudan is the territory south of the 22nd parallel.
    Sources
    en.wikipedia.org/wiki/Egypt–Sudan_border; treaty text: en.wikisource.org/wiki/Sudan_Convention_(1899)

  6. Algeria, Mali, Niger: nearly 1,700 kilometres of ruler-straight border.

    Fact
    753 km (Algeria–Mali) + 942 km (Algeria–Niger) = 1,695 km of straight runs.
    Source
    Our own measurement of the detected straight runs on Natural Earth 1:50m (on screen: “measured · Natural Earth 1:50m”). See map data.

  7. Namibia and Botswana? Two meridians and a parallel.

    Fact
    The boundary follows 20°E, 22°S and 21°E (plus the Caprivi Strip), set by the Anglo-German Agreement of 1 July 1890.
    Source
    The agreement as quoted in International Court of Justice, Kasikili/Sedudu Island (Botswana/Namibia), judgment of 13 December 1999, icj-cij.org/node/103865

  8. About 44% of Africa's borders follow latitude or longitude.

    Fact
    Barbour (1961) classified boundaries in inter-tropical Africa as 44 % astronomical lines (parallels and meridians), 30 % mathematical lines and 26 % physical features.
    Note
    The script says “latitude or longitude”, not “straight lines”: counting all mathematical lines would give 74 %. Paine, Qiu and Ricart-Huguet note that Barbour's base is Hertslet (1909) and estimate that 37 % of borders are straight today. Shown on screen as “≈44 %”.
    Sources
    Barbour, K. M. (1961), “A geographical analysis of boundaries in inter-tropical Africa”, in Essays on African Population; cited in Paine, J., Qiu, X. and Ricart-Huguet, J. (2024), “Endogenous Colonial Borders: Precolonial States and Geography in the Partition of Africa”, American Political Science Review, cambridge.org (APSR)

  9. Drawn in Europe. Lived in Africa.

    Basis
    Summary of the claims above: the rules were set in Berlin and the lines in treaties signed in European capitals such as Paris, London and Lisbon.

Added in the long cut

  1. The ruler even left a gap. Bir Tawil: 2,000 square kilometres that no country claims.

    Fact
    Egypt claims the political line of 1899 (22°N), Sudan the administrative line of 1902. As a result Hala'ib is claimed by both and Bir Tawil by neither. Area 2,060 km²; a quadrilateral with a northern edge of 95 km and a southern edge of 46 km.
    Note
    Wikipedia's wording is “not claimed by any recognised government”. Bir Tawil is not in the Natural Earth data, so the on-screen shape is drawn from the published edge lengths and marked “schematic”.
    Source
    en.wikipedia.org/wiki/Bir_Tawil (citing the 1899 Anglo-Egyptian Agreement and the 1902 administrative boundary)

  2. Egypt and Libya: the 25th meridian, agreed with Italy in 1925.

    Fact
    The Egypt–Libya border follows the 25th meridian east south to the tripoint at Jebel Uweinat. Egypt and Italy signed the treaty on 6 December 1925 (Egypt ratified it in 1932–33; the northern section was delimited in 1926–27 and marked with pillars).
    Sources
    en.wikipedia.org/wiki/Egypt–Libya_border; treaty text at lawsociety.ly, “Agreement concerning the western borders of Egypt, 1925”

  3. Kenya and Tanzania? One straight line, with a kink around Kilimanjaro. Not a royal gift. A deal, 1886.

    Fact
    The Anglo-German Agreement of 1 November 1886 runs the line from the mouth of the Umba river to Lake Jipe, skirting the northern slope of the Kilimanjaro range, to the eastern shore of Lake Victoria at 1°S.
    Myth
    The story that Queen Victoria gave Kilimanjaro to her grandson as a birthday gift has no evidence behind it; in 1886 Wilhelm was not yet emperor (Heinz Schneppen).
    Sources
    German History in Documents and Images, “Anglo-German Agreement of 1886” (germanhistorydocs.org, document 782); Wikipedia, “German East Africa”; on the myth: ntz.info/gen/n01579.html (“Kilimanjaro: Border”, quoting Schneppen)

  4. Libya and Chad? Straight lines from 1955. In 1994 the World Court said: they stand.

    Status
    optional beat Only in the cut if the longer version is used.
    Fact
    The Libya–Chad boundary was defined by the Franco-Libyan Treaty of 10 August 1955: straight lines between 24°E/19°30'N, the Tropic of Cancer/16°E and 15°E/23°N. The International Court of Justice confirmed it on 3 February 1994, by 16 votes to 1.
    Sources
    ICJ, Territorial Dispute (Libyan Arab Jamahiriya/Chad), summary of the judgment of 3 February 1994, icj-cij.org/node/103836; case page icj-cij.org/case/83

Map data and measurements

The map is drawn from Natural Earth 1:50m country data (via the world-atlas package) in a Mercator projection, which keeps parallels and meridians straight. No map tiles are used.

Straight borders are detected in code: for every pair of neighbouring African countries the shared border is walked, and a run counts as straight if its chord-to-path ratio is at least 0.993, its maximum deviation is at most 1.2 % of the chord, no sub-segment turns more than 7° and it is at least 110 km long. At this resolution that gives 64 runs and about 18,500 km, roughly 25 % of internal border length.

Lengths of individual straight runs used in the episode: Algeria–Mali 753 km, Algeria–Niger 942 km, Egypt–Libya 799 km, Kenya–Tanzania 655 km, Libya–Chad 1,051 km.

The 14 flags in the Berlin scene are period flags of 1884, drawn in code; some are simplified (arms and crowns left out).

Corrections

None so far. If you find an error, write to . Corrections are listed here with the date.