Some domesticated plants spread astonishingly far.
Wheat and barley moved across huge portions of Eurasia.
Rice spread from China across much of Asia.
Maize moved far beyond Mesoamerica.
Pearl millet expanded beyond West Africa.
Other crops remained geographically restricted.
Why?
The article highlights two especially important variables:
time and productivity.
Older crops had longer to travel
A crop domesticated several thousand years earlier simply had more opportunities to spread through migration and exchange.
But age is not enough.
Agricultural productivity influences human demography.
Productivity changes population movement
A highly productive crop can support relatively high population densities.
Under lower productivity, communities may reach the effective carrying capacity of a local environment more quickly.
This can encourage group fission.
Some people establish new settlements.
Crops travel with them.
Paradoxically, under certain circumstances a less productive agricultural system might therefore promote faster territorial expansion.
Carrying capacity is not fixed
The paper wisely treats carrying capacity as “notional.”
A landscape does not possess one permanent human carrying capacity.
It changes with:
technology,
labour,
crop choice,
soil management,
climate,
water availability,
and cultivation strategy.
Humans continually modify the ecological ceiling they are approaching.
Some forgotten crops may simply have missed history's transport network
A crop remaining local does not necessarily mean it is agronomically inferior.
Historical circumstances matter.
Enset in Ethiopia, oca in the Andes and browntop millet in India are examples discussed in the paper of crops whose geographical spread remained limited.
Their unrealised agricultural potential may therefore be considerable.
History's winners are not automatically biology's best candidates.
Sometimes they were simply the crops standing nearest the door when human populations began moving.
###################################################################################
Further reading: This post is inspired by and draws on Dorian Q. Fuller, Tim Denham, and Robin Allaby, “Plant domestication and agricultural ecologies,” Current Biology 33, no. 11 (2023): R636–R649, doi:10.1016/j.cub.2023.04.038. Read the original article in Current Biology
For a classic and highly readable perspective on why plant domestication arose in some regions but not others, see Jared Diamond, Chapter 8, “Apples or Indians: Why Did Peoples of Some Regions Fail to Domesticate Plants?”, in Guns, Germs, and Steel: The Fates of Human Societies (W. W. Norton, 1997), pp. 131–156. Read “Apples or Indians” View Guns, Germs, and Steel on Google Books
###################################################################################
No comments:
Post a Comment