Skip to main content

Axis-orientation and knowledge transmission: evidence from the Bantu expansion


This paper empirically examines Jared Diamond’s axis-orientation technology transmission hypothesis in the context of Sub-Saharan African agriculture. Consistent with Diamond (Guns, germs and steel: a short history of everybody for the last 13,000 years. Vintage, 1998), societies in southern Africa whose ancestors migrated directly south from west-central Africa—through the rainforest—engage in different types of agricultural activities than societies whose ancestors migrated east—around the rainforest. In particular, those whose ancestors could consistently keep livestock and produce traditional dry-crops throughout their multigenerational migration journey are more likely to engage in these activities today. The differential preference for wet-crop production by those with a rainforest ancestry led to settlements being established in different types of locations. The data suggests that these initial atypical settlement location preferences led to more geographically and culturally isolated societies. This may have disadvantaged these groups with respect to the adoption of any new agricultural goods or processes.

This is a preview of subscription content, access via your institution.

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5


  1. 1.

    They also have more insular institutions. Meanwhile, an examination of differences in institutions on other dimensions yields no clear patterns, and indeed it is difficult to find any evidence of other possible reasons for the observed low levels of general crop adoption.

  2. 2.

    Only Bantu had settled agriculture at this time, and accordingly could support much larger societies.

  3. 3.

    One concern is that Diamond’s theory may have informed historical population estimates in the generation of the data.

  4. 4.

    The specification was tested as a binary and a continuous variable, and it makes little difference to the direction or precision of the estimates.

  5. 5.

    A histogram of the population per square d.d. is in Fig. 4.

  6. 6.

    The 10th percentile of the population distribution, conditional on any inhabitants is 305 according to the Klein Goldewijk and Stehfest (2017) data.

  7. 7.

    There may be concern about selection on the southern rainforest boundary as well. A similar exercise looking at land characteristics faced by migrants as they potentially exit the rainforest is seen in Table A1, and the results are nearly identical.

  8. 8.

    See Table A2 columns 1 and 2 for regressions that place these variables as outcomes. In each case there appears to be no correlation between the variable and rainforest ancestry.

  9. 9.

    As the table demonstrates, this is true for any of the historical outcomes examined in the paper.

  10. 10.

    Robustness to using both the Klein Goldewijk and Stehfest (2017) data and the McEvedy (1978) data, as well as using different time-periods can be seen in Table A4.

  11. 11.

    Another plausible explanation could be that tastes for particular crops develop. Evidence suggests that societies are willing to take-on substantial costs to produce goods they have developed a taste for (Atkin 2016). The argument against this machanism explaining the observed cropping patterns in the Bantu context is in section D.

  12. 12.

    This is accomplished by taking disaggregated population maps and matching them geographically to the Murdoch ethnic homelands map.

  13. 13.

    Interestingly, southern migrants also adopted institutions that have more insular features than the relatively outward-oriented eastern migrants, despite that other institutional features appear relatively similar (Table A6).

  14. 14.

    For instance, one reason we might expect that livestock was not readopted is that—despite the arguments put forth by the history literatures—there were in fact strong selection effects, and that today those with a rainforest ancestry simply are not physically adept at certain tasks. Alternatively, it may have nothing to do with good-specific skills or abilities. Instead, it could be that nothing is being shared by neighbours, or adopted by these groups.

  15. 15.

    See Table A7 for a summary of crops considered, their origins, and the timing of their introduction to Africa.

  16. 16.

    One remaining concern could be that the locations of production based on ethnic homelands are no longer the locations where people live. To address this, I also match agricultural production to current locations of people in the Afrobarometer. Still, accounting for migration, we find exactly the same patterns in the data (for details see Sect. C).

  17. 17.

    That is, ones that are unprofitable in the rainforest, but profitable outside of it


  1. Ashraf, Q., & Galor, O. (2013a). Genetic diversity and the origins of cultural fragmentation. American Economic Review, 103(3), 528–33.

    Article  Google Scholar 

  2. Ashraf, Q., & Galor, O. (2013b). The “out of africa” hypothesis, human genetic diversity, and comparative economic development. American Economic Review,103(1), 1–46.

  3. Ashraf, Q., Özak, Ö., & Galor, O. (2010). Isolation and development. Journal of the European Economic Association, 8(2–3), 401–412.

    Article  Google Scholar 

  4. Atkin, D. (2016). The caloric costs of culture: Evidence from indian migrants. American Economic Review, 106(4), 1144–1181.

    Article  Google Scholar 

  5. Beusen, A., Doelman, J., Klein Goldewijk, K., & Stehfest, E. (2017). Anthropogenic land use estimates for the holocene; hyde 3.2. Earth System Science Data, 9, 927–953.

    Article  Google Scholar 

  6. Binford, L. R. (1980). Willow smoke and dogs’ tails: hunter-gatherer settlement systems and archaeological site formation. American Antiquity, pp. 4–20.

  7. Blouin, A., & Dyer, J. (2021). How cultures converge: An empirical investigation of trade and linguistic exchange. University of Toronto Working Papers, 691, February.

    Google Scholar 

  8. Colella, F., & Lalive, R. (2019). Seyhun Orcan Sakalli, and Mathias Thoenig. Inference with Arbitrary Clustering.

  9. Comin, D., Easterly, W., & Gong, E. (2010). Was the wealth of nations determined in 1000 bc? American Economic Journal: Macroeconomics, 2(3), 65–97.

    Google Scholar 

  10. Desmet, K., Ortuño-Ortín, I., & Wacziarg, R. (2011). The political economy of linguistic cleavages. Journal of Development Economics

  11. Diamond, J. (1998). Guns, Germs and Steel: a short history of everybody for the last 13,000 years. Vintage.

  12. Dickens, A. (2018). Population relatedness and cross-country idea flows: evidence from book translations. Journal of Economic Growth, 23(4), 367–386.

    Article  Google Scholar 

  13. Dickens, A. (2021). Understanding ethnolinguistic differences: The roles of geography and trade. Unpublished manuscript: Brock University.

  14. Flight, C. (1980). Malcolm guthrie and the reconstruction of bantu prehistory. History in Africa, 7: pp. 81–118. ISSN 03615413.

  15. Giuliano, P., & Nunn, N. Understanding cultural persistence and change. Review of Economic Studies (forthcoming)

  16. Guthrie, M. (1948). The classification of the Bantu languages. Pub. London; New York: for the International African Institute by the Oxford Univ. Press.

    Google Scholar 

  17. Henderson, V., Storeygard, A., & Weil, D. N. (2011). A bright idea for measuring economic growth. American Economic Review, 101(3), 194–199.

    Article  Google Scholar 

  18. Hibbs, D. A., & Olsson, O. (2004). Geography, biogeography, and why some countries are rich and others are poor. Proceedings of the National Academy of Sciences, 101(10), 3715–3720.

    Article  Google Scholar 

  19. International Food Policy Research Institute. Global Spatially-Disaggregated Crop Production Statistics Data for 2010 Version 2.0.

  20. Laitin, D., & Robinson, A. (2011). The continental axis theory revisited.

  21. Laitin, D. D., Moortgat, J., & Robinson, A. L. (2012). Geographic axes and the persistence of cultural diversity. Proceedings of the National Academy of Sciences, 109(26), 10263–10268.

    Article  Google Scholar 

  22. Leff, B., Ramankutty, N., & Foley, J. A. (2004). Geographic distribution of major crops across the world. Global Biochemical Cycles,18(GB1009)

  23. Lewis, P. M. (2009). Ethnologue: Languages of the World. SIL International, Dallas: Texas, sixteenth edition.

    Google Scholar 

  24. McEvedy, C. Atlas of world population history. Penguin, Harmondsworth; New York [etc.], (1978). ISBN 9780140510768.

  25. Michalopoulos, S. (2011). The origins of technolinguistic diversity. Economics Working Papers 0095, Institute for Advanced Study, School of Social Science.

  26. Michalopoulos, S. (2012). The origins of ethnolinguistic diversity. American Economic Review, 102(4), 1508–1539.

    Article  Google Scholar 

  27. Michalopoulos, S., Naghavi, A., & Prarolo, G. (2018a). Trade and geography in the spread of Islam. The Economic Journal, 128(616), 3210–3241.

    Article  Google Scholar 

  28. Michalopoulos, S., Putterman, L., & Weil, D. N. (2018b). The Influence of Ancestral Lifeways on Individual Economic Outcomes in Sub-Saharan Africa. Journal of the European Economic Association, 17 (4): 1186–1231, 09. ISSN 1542-4766.

  29. Moon, Z. K. & Farmer, F. L. (2001). Population density surface: A new approach to an old problem. Society & Natural Resources, 14 (1): 39–49. ISSN 0894-1920.

  30. Morris, M. L., & Byerlee, D. (1993). Narrowing the wheat gap in sub-saharan Africa: a review of consumption and production issues. Economic Development and Cultural Change, 41(4), 737–761.

    Article  Google Scholar 

  31. Murdock, G. P. (1959). Africa: Its peoples and their culture history. New York [u.a.]: McGraw-Hill.

  32. Nunn, N., & Wantchekon, L. (2012). The slave trade and the origins of mistrust in Africa. American Economic Review, 101(7), 3221–52.

    Article  Google Scholar 

  33. Oliver, R. (1966). The problem of the bantu expansion. Journal of African History, 7(3), 361–376.

    Article  Google Scholar 

  34. Olsson, O., & Hibbs Jr, D. A. (2005). Biogeography and long-run economic development. European Economic Review, 49(4), 909–938.

    Article  Google Scholar 

  35. Pavlik, J. B., & Young, A. T. (2019). Did technology transfer more rapidly east-west than north-south? European Economic Review, 119, 216–235.

    Article  Google Scholar 

  36. Plaza, S., Salas, A., Calafell, F., Corte-Real, F., Bertranpetit, J., Carracedo, Á., & Comas, D. (2004). Insights into the western bantu dispersal: MTDNA lineage analysis in angola. Human Genetics, 115(5), 439–447.

    Article  Google Scholar 

  37. Putterman, L., & Weil, D. N. (2010). Post-1500 Population Flows and The Long-Run Determinants of Economic Growth and Inequality*. The Quarterly Journal of Economics, 125 (4): 1627–1682, 11 . ISSN 0033-5533.

  38. Vansina, J. (1990). Paths in the rainforests: Toward a history of political tradition in equatorial Africa. Madison Wis.: University of Wisconsin Press. 9780299125707

Download references

Author information



Corresponding author

Correspondence to Arthur Blouin.

Additional information

Publisher's Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

I would like to thank Oded Galor for very clear and helpful editorial guidance, and two anonymous referees for constructive comments that improved the paper substantially. I am also grateful to Sasha Becker, Loren Brandt, Nick Crafts, Shari Eli, James Fenske, Price Fishback, Oded Galor, Bishnupriya Gupta, Victor Lavy, Rocco Macchiavello, Stelios Michalopoulos, Sharun Mukand, Elias Papaioannou, Tavneet Suri, Anand Swamy, Fabian Waldinger and Chris Woodruff for helpful comments over the life of this project. I also thank seminar and conference participants at EEA, EHS, NEUDC, CEA, Brown University and the University of Warwick. I gratefully acknowledge CAGE financial support.

Supplementary Information

Below is the link to the electronic supplementary material.

Supplementary material 1 (pdf 1381 KB)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Blouin, A. Axis-orientation and knowledge transmission: evidence from the Bantu expansion. J Econ Growth 26, 359–384 (2021).

Download citation


  • Knowledge transmission
  • Axis orientation
  • Isolation
  • Agricultural production