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.
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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.
Only Bantu had settled agriculture at this time, and accordingly could support much larger societies.
One concern is that Diamond’s theory may have informed historical population estimates in the generation of the data.
The specification was tested as a binary and a continuous variable, and it makes little difference to the direction or precision of the estimates.
A histogram of the population per square d.d. is in Fig. 4.
The 10th percentile of the population distribution, conditional on any inhabitants is 305 according to the Klein Goldewijk and Stehfest (2017) data.
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.
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.
As the table demonstrates, this is true for any of the historical outcomes examined in the paper.
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.
This is accomplished by taking disaggregated population maps and matching them geographically to the Murdoch ethnic homelands map.
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).
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.
See Table A7 for a summary of crops considered, their origins, and the timing of their introduction to Africa.
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).
That is, ones that are unprofitable in the rainforest, but profitable outside of it
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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.
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Blouin, A. Axis-orientation and knowledge transmission: evidence from the Bantu expansion. J Econ Growth 26, 359–384 (2021). https://doi.org/10.1007/s10887-021-09196-9
- Knowledge transmission
- Axis orientation
- Agricultural production