192 | Nature | Vol 581 | 14 May 2020
Article
indicating that plant cultivation in the Neotropics started in shrub savan-
nahs as well as seasonal tropical forest environments^4. It does not come as
a surprise that phytoliths derived from plants that produce underground
storage organs—including Manihot, Calathea and other Marantaceae,
Heliconia, Cyperaceae and Phenakospermum—constitute an important part
of the total phytolith assemblages from the forest islands of the Llanos de
Moxos. These plants are abundant in savannahs and produce carbohydrate-
rich foods that, with the exception of some varieties of manioc^26 , are easy to
process and cook. Today, they are consumed by indigenous groups^19 and
they probably provided a considerable part of the calories consumed by
the first inhabitants of the Llanos de Moxos. The large herbivores and fish
available in the savannahs^12 ,^13 would have complemented a mixed economy.
The fertile forest islands were probably the home gardens in which these
crops were cultivated. Our data are consistent with the hypothesis that
plants that produce underground storage organs were a fundamental
part of the diet of human populations as they colonized new territories^27 ,^28.
Implications for biodiversity
Our results show that inland savannahs were a key region for the early
occupation of the Neotropics, and that these savannahs began to be
transformed by the arrival of very early human settlers. Anthropic forest
islands are entirely artificial, and do not take advantage of pre-existing
landscape features. Their formation is not only an incidental effect
of food-waste dumping, but can also be seen as an active process of
niche construction^29. These accumulative middens constituted fertility
hotspots amid poor savannah soils, because (i) they were loci for the
accumulation of nutrients that came from gathering activities in the
surrounding savannah and (ii) they remained above the water level
during the wet season^12. It is only after 4,000 years bp, when the old
and infertile soils of the south of the Llanos de Moxos were covered
with fertile alluvium deposited by the Río Grande, that agriculture in
the savannahs was facilitated^30. Overall, the early-to-mid-Holocene4,826–4,103
5,475–4,4376,163–5,243
6,256–5,5156,923–6,321
7,443–6,6017,839–7,020
8,095–7,547
8,150–7,9558,270–8,025
8,354–8,1758,826–8,1926,707–5,826
7,350–6,9458,530–7,965
9,212–8,6656,306–6,186
5,288–4,965
10,284–10,19610,546–10,231
13,918–10,307
496–328
2,701–2,0942,465–2,327
4,785–4,424
4,965–4,840
5,295–4,5835,857–5,595
6,730–5,472
6,409–6,0256,443–6,380
6,659–6,3996,953–6,322
6,984–6,6957,145–6,730
7,239–6,945
7,552–6,9517,486–7,325
7,828–7,6807,954–7,718
8,696–8,413
8,985–8,6498,999–8,717
9,560–9,4389,671–9,537
10,155–9,63210,186–9,766Cal. yrBP20–300–10
30–4040–50
90–10060–70
110–115130–140
150–160
170–180190–200
200–210210–220
220–230230–24029–340–10
39–4448–54
69–7480–84
108–113140–145
160–164
0–10
20–3030–40
40–5050–60
80–90
110–12090–100
80–90
100–110120–130
150–160
40–50
160–17090–100
90–95
170
110–120^65
200–210
80–90 100
130–140 170
190–20060–70
250–260
230–24085–90
92–97 190
270
145–150 220
182–18795–100
270–280 150
140
90–10030–40
110–120
160–170Depth (cm below surface)(^569521)
530
FIN 12 423
(^502536)
(^527574)
519
(^569421)
(^570535)
(^526430)
FIN14
FIN 5 433
FIN 15^434
FIN 3^429
FIN 8
(^575493)
433
(^569565)
(^560565)
Sites
Isla del Tesoro
La Chacra
San Pablo
Isla Manechi
02040
BambusoideaeOryza
sp., seed
- 0612
Cyperaceaecf.
Calathea
sp., root
0612
Heliconia
sp.^
Heliconia
sp., root*
0612
Marantaceae
036
Marantaceae, rhizome/seed
Z. mays
, cob
024
Cucurbita
sp., rind
Manihot
012
Celtis
sp., fruit/seed*
036
Arecoideae, hat-shaped
04080
Total palms
04080
Total arboreal
Poaceae Herbs Cultigens
Fig. 2 | Diagram showing the percentage of the most relevant phytolith
groups from anthropic forest islands. Dots indicate presence ≤ 1% (for more
details, see Extended Data Fig. 2, Extended Data Table 1). Asterisks denote
nondomesticated edible plants that are used as food resources today^35.
Phytolith percentages are based on a minimum of 200 diagnostic phytoliths
counted per slide.