SCIENCE science.org 22 APRIL 2022 • VOL 376 ISSUE 6591 359PHOTO: ALEX WILD
By Julio C. Postigo^1 and Joan E. Strassmann^2T
he chicken, potatoes, and chickpeas
on our dinner plates each come from
different places where humans tran-
sitioned from casual to intense rela-
tionships with the animals and plants
that sustain us. These transitions
happened in at least 12 and
probably more than 20 differ-
ent places 4000 to 21,000 years
ago in times of stable and im-
proving climate ( 1 ).
Some insects have been agri-
culturalists for tens of millions
of years longer than humans.
It is therefore possible that we
can learn from their agricultural
practices to both improve our
own and to see what our future
might hold. In June 2019, Ted
Schultz, Richard Gawne, and
Peter Peregrine brought together a team of
experts for the 38th Altenberg Workshop in
Theoretical Biology to consider this possibil-
ity. The Convergent Evolution of Agriculture
in Humans and Insects synthesizes the out-
comes of this event.AGRICULTUREBOOKS et al.
Animal agriculturalists
The researchers present at the workshop
agreed that agriculture is “cultivation on a
large scale in which the farmer has become
obligately dependent on the cultivated species
for nutrition.” Agriculture itself they expected
to be preceded by cultivation and domesti-
cation, where the former simply facilitates
growth and proliferation of the crop, be it
animal or plant, and the latter
requires some form of genetic
change that makes the crop more
suitable for the farmer and less
able to proliferate on its own.
This book discusses many
forms of animal agriculture, but
its focus is on the relationship be-
tween macrotermitine termites
and Termitomyces fungi more
than 24 million years ago and
the relationship between attine
ants and their fungi more than
55 million years ago. In each of
these cases, domestication of the fungus arose
only once and caused their hosts to proliferate,
making them dominant in their ecosystems.
Perhaps the most interesting message
from observing animal rearing of both crops
and animals is that the crops are nearly al-
ways clonal. This is true for higher termites
and leaf-cutting ants, for damselfish that
prune their algae gardens, for ambrosia bee-
tles seeding their wood tunnels with fungi,
and for ant queens that take their matingflight with a single mealy bug gently held in
their mandibles. Clonality eradicates within-
crop evolutionary conflict. Such conflict re-
duces productivity, causing plants to invest
more in stems to overtop neighboring plants
than in seeds, for example.
The role of clonality or high relatedness
among crop plants is something R. Ford
Denison explores in depth in chapter 3.
While clonality may solve within-crop con-
flict, it introduces another problem: A sin-
gle clone will be much more easily defeated
by diseases and competitors, although this
is less of a problem if individual farmers
tend different clones. Other chapters look
at the morphological consequences of ag-
riculture for both humans (Menéndez and
Buck, chapter 12) and their crops (Gawne
and McKenna, chapter 13), emphasizing the
complexity of trade-offs.
There are many organisms that depend
on symbionts for nutrition. The fungus in a
lichen symbiosis depends on the algae or the
dinoflagellate it entraps. Coral polyps are
animals that depend on plant zooxanthellae
for nutrition ( 2 ). These symbioses between
animals or fungi and plants or dinoflagellates
involve the cultivation, domestication, and
ultimately mutual dependence between two
different organisms. These crops are also of-
ten clonal for the same reasons as agricultural
crops. What, then, constitutes agriculture?
Perhaps the difference between these
symbioses and those relationships we call ag-
riculture lies only in that agriculture requires
deliberate action and behavior and the other
symbioses arise from processes that occur at
the physiological or cellular level. But is this
really a meaningful difference? If ants and
termites cultivated plants rather than fungi,
they would not have to perform the behavior
of bringing in food, because plants and dino-
flagellates grab their carbon from the air.
Termites and attine ants have transformed
their ecosystems. But we have taken these
transformations even farther, sowing single
crops on thousands of acres of the planet.
Indeed, there is very little space left for hu-
man agricultural expansion ( 3 ). Perhaps if
we paid more attention to how insects farm,
we might learn more about reducing compe-
tition between domesticated plants and ani-
mals, thereby increasing yield and reducing
the need for more land. jREFERENCES AND NOTES- P. H. Kavanagh et al., Nat. Hum. Behav. 2 , 478 (2018).
- A. E. Douglas, The Symbiotic Habit (Princeton Univ.
Press, 2010). - Y. M. Bar-On, R. Phillips, R. Milo, Proc. Natl. Acad. Sci.
U.S.A. 115 , 6506 (2018).
10.1126/science.abq2570
The tropical ant species Cyphomyrmex
rimosus farms yeast.The Convergent
Evolution of Agriculture
in Humans and Insects
Ted R. Schultz, Richard Gawne,
Peter N. Peregrine, Eds.
MIT Press, 2022. 338 pp.The reviewers are at the^1 Department of Geography,
Indiana University Bloomington, Bloomington, IN 47405,
USA; and^2 Department of Biology, Washington University in
St. Louis, St. Louis, MO 63130, USA. Email: [email protected];
[email protected]There is much to learn from the farming practices of ants,
termites, and other insects