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Cannabis in Asia: its center of origin and early cultivation, based on a synthesis of subfossil pollen and archaeobotanical studies

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Biogeographers assign the Cannabis centre of origin to “Central Asia”, mostly based on wild-type plant distribution data. We sought greater precision by adding new data: 155 fossil pollen studies (FPSs) in Asia. Many FPSs assign pollen of either Cannabis or Humulus (C–H) to collective names (e.g. Cannabis/Humulus or Cannabaceae). To dissect these aggregate data, we used ecological proxies. C–H pollen in a steppe assemblage (with Poaceae, Artemisia, Chenopodiaceae) was identified as wild-type Cannabis. C–H pollen in a forest assemblage (Alnus, Salix, Quercus, Robinia, Juglans) was identified as Humulus. C–H pollen curves that upsurged alongside crop pollen were identified as cultivated hemp. Subfossil seeds (fruits) at archaeological sites also served as evidence of cultivation. All sites were mapped using geographic information system software. The oldest C–H pollen consistent with Cannabis dated to 19.6 ago (Ma), in northwestern China. However, Cannabis and Humulus diverged 27.8 Ma, estimated by a molecular clock analysis. We bridged the temporal gap between the divergence date and the oldest pollen by mapping the earliest appearance of Artemisia. These data converge on the northeastern Tibetan Plateau, which we deduce as the Cannabis centre of origin, in the general vicinity of Qinghai Lake. This co-localizes with the first steppe community that evolved in Asia. From there, Cannabis first dispersed west (Europe by 6 Ma) then east (eastern China by 1.2 Ma). Cannabis pollen in India appeared by 32.6 thousand years (ka) ago. The earliest archaeological evidence was found in Japan, 10,000 bce, followed by China.
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Vol.:(0123456789)
1 3
Vegetation History and Archaeobotany
https://doi.org/10.1007/s00334-019-00731-8
REVIEW
Cannabis inAsia: its center oforigin andearly cultivation, based
onasynthesis ofsubfossil pollen andarchaeobotanical studies
JohnM.McPartland1,2· WilliamHegman3· TengwenLong4
Received: 20 December 2018 / Accepted: 6 May 2019
© Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract
Biogeographers assign the Cannabis centre of origin to “Central Asia”, mostly based on wild-type plant distribution data.
We sought greater precision by adding new data: 155 fossil pollen studies (FPSs) in Asia. Many FPSs assign pollen of either
Cannabis or Humulus (CH) to collective names (e.g. Cannabis/Humulus or Cannabaceae). To dissect these aggregate data,
we used ecological proxies. CH pollen in a steppe assemblage (with Poaceae, Artemisia, Chenopodiaceae) was identified as
wild-type Cannabis. CH pollen in a forest assemblage (Alnus, Salix, Quercus, Robinia, Juglans) was identified as Humulus.
CH pollen curves that upsurged alongside crop pollen were identified as cultivated hemp. Subfossil seeds (fruits) at archaeo-
logical sites also served as evidence of cultivation. All sites were mapped using geographic information system software.
The oldest CH pollen consistent with Cannabis dated to 19.6 ago (Ma), in northwestern China. However, Cannabis and
Humulus diverged 27.8Ma, estimated by a molecular clock analysis. We bridged the temporal gap between the divergence
date and the oldest pollen by mapping the earliest appearance of Artemisia. These data converge on the northeastern Tibetan
Plateau, which we deduce as the Cannabis centre of origin, in the general vicinity of Qinghai Lake. This co-localizes with the
first steppe community that evolved in Asia. From there, Cannabis first dispersed west (Europe by 6Ma) then east (eastern
China by 1.2Ma). Cannabis pollen in India appeared by 32.6 thousand years (ka) ago. The earliest archaeological evidence
was found in Japan, 10,000 bce, followed by China.
Keywords Cannabis sativa· Humulus lupulus· Cannabaceae· Biogeography· Centre of origin· GIS
Introduction
Cannabis holds significance in human history and life today
as a triple-use crop. First, its fruits (seeds) provide valuable
protein and essential fatty acids. Archaeological evidence in
a food context dates back to 10,000 bp, in Japan (Kobayashi
etal. 2008). Its bast cells supply fibres, for cordage and tex-
tiles. Carbonized hemp fibres, found with silk and spinning
wheels, date to 5,600 bp, in Henan Province, China (Zhang
and Gao 1999). Its flowering tops produce cannabinoids,
which have been used for medicinal, shamanic, and recrea-
tional purposes. Archaeological evidence of drug use dates
to 2,700 bp, in Xinjiang region (Russo etal. 2008; Jiang
etal. 2016).
Despite a voluminous literature emerging in the last three
decades, the classification of Cannabis and its centre of ori-
gin remains under debate. A single species concept (Small
and Cronquist 1976) has support from measures of popula-
tion differentiation, such as FST (Sawler etal. 2015; Lynch
etal. 2016) and barcode gaps (McPartland 2018). Other bot-
anists recognize several Cannabis species (Hillig and Mahl-
berg 2004; Clarke and Merlin 2013). Hypotheses regarding
the Cannabis centre of origin began with Ibn Wahshīyah in
930 ce. He proposed that šāhdānaj was brought to Babylon
from India or perhaps China (Hämeen-Anttila 2006). De
Communicated by F. Bittmann.
Electronic supplementary material The online version of this
article (https ://doi.org/10.1007/s0033 4-019-00731 -8) contains
supplementary material, which is available to authorized users.
* John M. McPartland
mcpruitt@myfairpoint.net
1 University ofVermont, Burlington, VT05405, USA
2 GW Pharmaceuticals, Sovereign House, Histon,
CambridgeCB249BZ, UK
3 Department ofGeography, Middlebury College, Middlebury,
VT05753, USA
4 School ofGeographical Sciences, University ofNottingham
Ningbo China, Ningbo315100, China
Vegetation History and Archaeobotany
1 3
Candolle (1883) offered Central Asia as the centre of origin
of C. sativa. His biogeographical theories were based upon
the distribution of wild-type plants, as well as linguistic,
historical, archaeological, and fossil data.
Print fossils (i.e. impressions of leaves or fruits in rocks)
of Cannabis are limited to only two collections: Friedrich
(1883a, b) found fossil leaves in Germany that he named
Cannabis oligocaenica. His species epithet indicates the
Oligocene epoch, 33.923.03 million years (Ma) ago.
Palamarev (1982) identified a fossil seed (fruit) as “Can-
nabis sp.” in Bulgaria. He dated the find to the late Miocene
(“Pontian age”, 7.35.3Ma). Dorofeev (1969) reported a
fossil seed, “Cannabis sp.”, from the Miocene in Siberia.
He subsequently re-identified the fossil as an extinct species,
Humulus irtyshensis (Dorofeev 1982). Humulus and Can-
nabis are sister genera, forming a phylogenetic clade within
the family Cannabaceae.
Contrary to the paucity of print fossils, hundreds of fossil
pollen studies (FPSs) have identified subfossil Cannabis pol-
len. Fröman (1939) first used pollen analysis to reconstruct
the history of Cannabis. Following analytical refinements
by Fries (1958), dozens of papers have been published.
This culminated with the elaborate meta-analysis by Dör-
fler (1990), followed by our own meta-analyses (Long etal.
2017; McPartland etal. 2018).
Cannabis pollen is often straightforward to recognize
(Mercuri etal. 2002), however, morphological similari-
ties between Cannabis and Humulus pollen grains have
prompted palynologists to use collective labels, e.g. Canna-
bis/Humulus or Cannabaceae. Significant labelling bias also
arises: Chinese FPS palynologists assign Cannabis pollen to
Humulus” (Li 1974), and northern European palynologists
often assign Humulus pollen to “Cannabis” (Wilson 1975).
Parsing Cannabis from Humulus may be more difficult
in Asia than in Europe. Five studies of Asian Cannabis (C.
sativa ssp. indica) indicate that pollen grain diameter is
smaller than that of European hemp (C. sativa ssp. sativa),
so the size of Asian Cannabis pollen falls within the range
of Humulus (literature in McPartland etal. 2018).
FPSs resorting to collective labels (hereafter abbreviated
CH pollen) have thwarted the study of Cannabis. Clarke
and Merlin (2013) reviewed dozens of Asian FPSs, and they
were flummoxed by FPSs that lumped data as CH pollen.
Long etal. (2017) synthesized 46 FPSs in their pan-Eurasian
study. They resolved the CH dilemma by limiting FPSs
to studies that explicitly identified pollen as Cannabis—a
strategy that excluded a lot of CH data.
McPartland et al. (2018) used ecological proxies,
instead of grain morphology, to differentiate CH pollen
as either Cannabis or Humulus pollen. Cannabis flourishes
in steppe—an open, treeless habitat. European phytosoci-
ologists and other field botanists report wild-type C. sativa
cohabitating with Poaceae, Artemisia, and Chenopodiaceae
(hereafter abbreviated PAC). Thus CH pollen in a steppe
assemblage (with PAC pollen) was identified as wild-type
Cannabis. Conversely, Humulus lupulus, a perennial herba-
ceous scandent, requires trees to climb. European phytosoci-
ologists and other field botanists report H. lupulus associat-
ing with Alnus, Populus, and Salix spp. (abbreviated ASP).
Thus CH pollen in a mesophytic forest assemblage (with
ASP pollen) was identified as Humulus.
Palynologists have noted correlations between Cannna-
bis and PAC, and between Humulus and ASP, and extended
these associations into the past. For supporting palynologi-
cal and phytosociological literature, see McPartland etal.
(2018). In this study, we aim to further develop this method,
focusing in particular on the Asia context. The ecological
proxies method will be applied to a multilingual collection
of Asian FPSs, to reconstruct the evolutionary and human-
related history of Cannabis in Asia.
Methods
FPS search strategy anddata analysis
We collated an FPS database using several internet search
engines (European Pollen Database, Web of Science, Google
Scholar) using keywords and Boolean operators: Asia AND
(palynology OR pollen) AND (Cannabis OR Humulus OR
Cannabaceae). This was repeated with Chinese characters
when searching Chinese-based references. Additional FPSs
were obtained through citation tracking—references in
retrieved publications were searched for antecedent sources,
and these were retrieved. To map pollen in space and time,
retrieved publications had to meet three inclusion criteria:
(1) precise geographical coordinates, (2) accurate chronol-
ogy, (3) a minimal threshold amount of pollen grains.
1. Precise geographical coordinates were localized to
within a hundredth degree of latitude and longitude.
Some studies did not provide geographical coordinates.
We obtained coordinates of those sites via Google Earth,
which uses World Geodetic System of 1984 (WGS84)
datum. Several FPSs were conducted at deep-water sites,
which explains sites located in seas and oceans. Geogra-
phers have debated the border between eastern Europe
and western Asia. We included three studies on the edge:
a deep-water site in the Black Sea off the coast of Tur-
key, a site in Georgia, and a cis-Ural site in Russia.
2. Accurate chronology necessitated restricting data to
FPSs with absolute dating, such as radiocarbon (14C),
optically stimulated luminescence (OSL), or magne-
tostratigraphical methods. We excluded studies that
assigned “relative dates” within sediments cores (i.e.
Vegetation History and Archaeobotany
1 3
dates inferred by changes in vegetation, such as the start
of the Holocene).
3. Palynologists debate the minimal amount of pollen
required to determine the local presence of a plant spe-
cies at a study site (versus pollen at a study site that
arrived via long distance transport). Bottema et al.
(2003) specifically mentioned CH pollen in the “prob-
lem of long-distance transport”. Several FPSs located
in south-western Asia had three or fewer CH pollen
grains. These rare grains likely blew in from Europe.
The Etesian winds blow from the Balkans (harbouring
endemic Cannabis) into Israel, Palestine, Lebanon, and
Egypt (Zecchetto and De Blasio 2007). For a retrieved
publication to be included in our study, CH pollen had
to appear in a minimum of five separate strata within
a stratigraphic core (for details see McPartland etal.
2018).
Ecological proxies intheAsia context
In Central and East Asia, Cannabis seems to have a stronger
alliance with Artemisia, less so with Poaceae and Chenopo-
diaceae. We took a closer look at Artemisia, to better pin-
point the Cannabis centre of origin. Artemisia and Cannabis
share parallel evolutionary patterns: In phylogenetic stud-
ies, Artemisia nests within the Antemideae subfamily (Zhao
etal. 2010), and Cannabis nests within the Cannabaceae
family (Yang etal. 2013). Artemisia evolved in Central/East
Asia during the late Eocene, ca. 3633.9Ma, out of the
worldwide Antemideae (Miao etal. 2011). Cannabis also
evolved in Central/East Asia, ca. 27.8Ma, out of the world-
wide Cannabaceae (McPartland 2018).
Artemisia and Cannabis are wind-pollinated and dioe-
cious. Both genera exhibit phenotypic plasticity, with adap-
tive phenotypes that respond to environmental changes,
enabling them to colonize new geographic locations. A
meta-analysis of FPSs in Europe showed that Cannabis and
Artemisia were fellow travellers; their geographic ranges
expanded and contracted in unison during, respectively,
glacial periods and warmer periods (McPartland etal. 2018).
Humulus pollen, in Central and East Asia, correlates with
ASP pollen, as well as Quercus, Betula, Juglans, Camellia,
and Robinia (abbreviated ASP +). Analysing Humulus pol-
len in East Asia is complicated by two additional species, H.
yunnanensis and H. japonicus (= H. scandans). H. yunnan-
ensis is a tree-climbing species limited to Yunnan province
(Zhou and Bartholomew 2003). It is a rare and endangered
plant (Hu and Wu 1992). No phytosociological studies have
been published that include H. yunnanensis.
H. japonicus is native to Japan, Korea, and eastern China
(Zhou and Bartholomew 2003), the Russian Far East (Maxi-
movich 1859), Vietnam and Laos (Pételot 1954). Phytosoci-
ological and field studies report H. japonicus in communities
dominated by trees—specifically Alnus (Lee etal. 1976; Kim
etal. 2010; Jeong etal. 2012; Lee etal. 2013), Salix (Kolbek
and Karolímek 2008; Kim etal. 2010; Oh etal. 2010; Jeong
etal. 2012; Lee etal. 2013), Quercus (Lee etal. 1976; Kol-
bek and Karolímek 2008; Kim etal. 2010; Oh etal. 2010),
Robinia (Lee etal. 1976; Kolbek and Karolímek 2008; Kim
etal. 2010; Jeong etal. 2012; Lee etal. 2013; Lee and Ahn
2014), and Camellia (Lee etal. 1976; Kim etal. 2010; Lee
and Ahn 2014; Eom and Kim 2017).
However, H. japonicus sometimes colonizes habitats
that overlap with those of Cannabis. These include ruderal
(Kolbek and Sádlo 1996; Oh etal. 2008) and riverside com-
munities (Jung and Kim 1998). Some riverside communi-
ties include Poaceae, Artemisia, or Chenopodiaceae in the
ground layer (Song and Song 1996; Jarolímek and Kolbek
2006; Balogh and Dancza 2008; Andrek etal. 2010). One
phytosociological study reports H. japonicus co-localizing
with C. sativa—a ruderal community in Korea (Kolbek
and Sádlo 1996). Maximovich (1859) reported H. japoni-
cus growing with C. sativa in the Amur region of the Rus-
sian Far East, and Clarke and Merlin (2013) photographed
feral hemp and H. japonicus growing together in Shandong
Province.
Despite these intermittent associations with herbaceous
plants, Asian palaeobotanists characterize Humulus as a
drought-intolerant climber of trees (Ni etal. 2010). They
treat Humulus pollen as a botanical marker of deciduous
broadleaved forests (Zhou etal. 2007), or tropical evergreen
forests (Lee and Liew 2010).
The ratio of non-arboreal pollen (NAP, pollen from
grasses, forbs, and sedges) and arboreal pollen (AP, tree pol-
len) serves as an indicator of landscape openness. NAP and
AP percentages are oppositional—when one goes down, the
other goes up. Similarly, palynologist have shown that Alnus
and PAC demonstrate oppositional characters (literature in
McPartland etal. 2018).
CH pollen can be identified as that of cultivated hemp
when its pollen count surges or becomes a continuous curve
in synchrony with pollen from other crop plants. This met-
ric was first adopted by Fries (1958) and used in ten other
palynological studies. Other crop plants include Avena
(oats), Hordeum (barley), Secale (rye), Triticum (wheat),
and Cerealia-type (undifferentiated cereal pollen).
The presence of Cannabis pollen in very high percentages
indicates a former hemp-retting site. Retting is a technical
term for rotting, a process that separates fibres from the rest
of the stalk. Soaking hemp stalks in water encourages bac-
terial growth and retting. When flowering male plants are
soaked in a retting-pond, large quantities of pollen settle
into pond sediments. Cannabis pollen 15% of TLP (total
land pollen) is usually considered evidence of hemp retting,
and percentages up to 97% have been reported (literature in
McPartland etal. 2018).
Vegetation History and Archaeobotany
1 3
Pollen algorithm
To differentiate CH pollen, the algorithm by McPartland
etal. (2018) was adjusted to account for Asian conditions.
We identified CH pollen as that of cultivated Canna-
bis when it appeared de novo along with crop pollen, or
increased at least twofold over earlier pre-Neolithic counts.
Several FPSs in South Asia report Cerealia pollen, attrib-
uted to agriculture, in ancient strata that clearly predate
archaeological evidence of grain cultivation (e.g. 12,000
bp, Quamar and Bera 2017). In these FPSs we looked for
twofold increases and continuous curves of CH pollen in
the presence of Cerealia pollen.
To differentiate CH pollen in pre-agricultural strata,
we used ecological proxies. When CH occurred in
a pollen assemblage where the NAP-to-AP ratio 2
(i.e. 66/33%), dominated by steppe vegetation (PAC), we
identified it as wild-type Cannabis. When CH occurred
in a pollen assemblage where the NAP/AP ratio 0.5
(i.e. 33/66%), in the presence of ASP+, we identified it
as Humulus. In some ambiguous FPSs, pollen counts of
PAC and ASP + rise and fall in near-synchrony, and the
NAP/AP ratio approaches 1:1 (i.e. 50/50%). At these sites,
we classified CH pollen as unresolved C/H.
Archaeobotanical evidence
We also included botanical evidence from archaeological
sites. Previous studies have collated archaeological reports
of hemp seeds, phytoliths, stalk fragments, fibre, cord-
age, or textiles, and pottery impressions of those materi-
als (Clarke and Merlin 2013; Long etal. 2017). McPart-
land and Hegman (2018) stratified the relative robustness
or validity of these materials. Microscopically-analysed
seeds, phytoliths, and stem fragments were considered the
most robust evidence. Fibre, cordage, and textiles were
problematic. For example, Song etal. (2017) unearthed
a few plant fibres identified as hemp, C. sativa, at a site
occupied by Palaeolithic hunter-gatherers that dates to
28.5ka. This could be the oldest hemp fibre ever found,
but their photomicrograph of a “hemp” fibre is by no
means convincing. Song etal. (2017) report plentiful flax
fibres at their site. McPartland and Hegman (2018) detail
the difficulties in differentiating hemp from flax fibre.
Regarding pottery impressions, identifying the plant spe-
cies that made the cord impression is even more difficult.
At least 14 plant species were utilized for pottery cord
impressions in Neolithic China (Kuhn 1988). In this cur-
rent study, we limited archaeological findings to micro-
scopic analyses of seeds, phytoliths, and stem fragments.
GIS mapping andbinning strategy
Latitude and longitude (referencing WGS84 datum) of each
FPS was plotted, using geographic information system (GIS)
software, ArcGISPro 2.2. The FPS sites were plotted on
three maps, corresponding to three binned time slices. Each
FPS site was notated with a symbol indicating pollen inter-
pretation—either wild-type Cannabis, Humulus, cultivated
Cannabis, or unresolved CH pollen. Archaeological sites
with hemp seeds or phytoliths were notated with another
symbol.
Stratigraphical data were binned intothree time
slices
Bin 1. This period includes the Oligocene (33.923.03Ma),
Miocene (23.035.3Ma), Pliocene (5.32.58Ma), and
Pleistocene (2.58Ma11.6 ka) epochs. The symbols for
these sites are sized according to the age of the pollen. A
weighted centroid for Cannabis pollen data was also calcu-
lated (weighted by geographical location and age).
Bin 2. Early- to Mid-Holocene, 11.55.0ka, a period of
improved climate, re-emerging forests, and the Mid-Holo-
cene Climatic Optimum. This period includes the onset of
agriculture in Asia and the earliest archaeobotanical evi-
dence of Cannabis usage.
Bin 3. Late-Holocene, 4.50ka, a period of profound
anthropogenic impact on landscapes, and the earliest
recorded Asian history.
Extrapolating intotheOligocene
McPartland (2018) constructed a maximum likelihood phy-
logenetic tree (PAUP* version 4.0b10) of 11 Rosales gen-
era, using rbcL + trnL-trnF sequences, and a nonparametric
variable rate-smoothing algorithm (r8s version 1.70), cali-
brated with four fossil date intervals (Boehmeria 60–34Ma,
Morus 56–34Ma, Celtis 65–56Ma, Humulus 28–16Ma).
The molecular clock estimated that Cannabis and Humu-
lus evolved (diverged) 27.8Ma. This date is bracketed by
other estimates: 87.3Ma (Boutain 2014), 24.8Ma (Wu etal.
2018), and 18.2Ma (Zhang etal. 2018b). Most of these
estimates predate the oldest Cannabis fossil pollen found in
this study (19.6Ma). Molecular-based divergence dates are
expected to predate fossil evidence, because fossil records
are fragmentary and incomplete (Parham etal. 2012). To
deduce the location of Cannabis during the temporal “miss-
ing link” between the molecular divergence date and the
oldest fossil pollen, we used two sets of indirect data.
Bosboom etal. (2011) mapped an “aridification zone”
arising in Central Asia at the Eocene–Oligocene bound-
ary, 34Ma. Orogenic changes at that time—the rise of the
Tibetan Plateau and the retreat of the Tarim Sea—forced
Vegetation History and Archaeobotany
1 3
concomitant changes in climate, resulting in the evolution
of steppe vegetation. China’s first steppe communities origi-
nated at the Eocene–Oligocene boundary (Sun etal. 2014),
and continued to develop through the Oligocene and Mio-
cene (Wang 1996), spanning the temporal missing link. We
transferred a best approximation of the palaeogeographic
map by Bosboom and colleagues onto a modern map of
Asia.
Secondly, we applied a previously reconstructed history
of Artemisia in Asia. Miao etal. (2011) tracked the spa-
tiotemporal appearance of Artemisia pollen, beginning at
the Eocene–Oligocene boundary, in a meta-analysis of 122
FPSs. As a proxy for the distribution of Cannabis prior to
our oldest pollen, we mapped their distribution of Artemi-
sia pollen, in six binned time slices used by Miao and col-
leagues: late Eocene (38–34Ma), latest Eocene (34Ma),
early Oligocene (34–28Ma), Oligocene (34–23Ma), early
Miocene (23–20Ma), and mid-Miocene (14Ma).
Results
The search strategy identified 173 FPSs that included CH
pollen or archaeological studies with seeds, phytoliths, or
stem fragments. Seven studies did not meet our inclusion
criteria, and another 11 studies reported duplicate data. The
remaining 155 studies were tabulated, each with a citation
number, study location, details regarding application of the
algorithm, and duplicate reports (ESM Table1). Excluded
studies were also tabulated, with exclusion criteria (ESM
Table2).
Bin 1 (19.6Ma11.6ka, Fig.1). The oldest CH pollen
consistent with Cannabis dated to 19.6Ma (early Miocene).
The site is located in Ningxia, China, on the border between
the Tibetan Plateau and the Loess Plateau. For scholars
interested in the original publication, see ESM Table1,
citation #1. During the Pliocene, Cannabis pollen occurs
in Northwest China (Ningxia, 2.6Ma, ESM Table1, #2).
During the first half of the Pleistocene (i.e. the Gelasian
and Calabrian ages, 2.58Ma-781ka), Cannabis pollen is
located in Bashkorostan, Russia (1.5Ma #156), Hebei Prov-
ince (1.2Ma #3), and the Russian Altai (787ka, #4).
During the latter half of the Pleistocene, Cannabis pollen
appears in four of six Chinese regions: Northwest China
(Shaanxi, 342ka, #5; Gansu, 145ka, #6; Shaanxi, 50ka, #8;
Shaanxi, 25ka, #12; Tibet, 20ka, #13; Xinjiang, 14.5ka,
#20; Gansu, 12ka, #28). North China (Inner Mongolia,
35ka, #9). Northeast China (Liaoning, 16Ma, #16; Jilin,
13ka, #24). East China (Shanxi, 15ka, #19). FPSs in two
remaining provinces, South Central and Southwest China,
have Humulus pollen but no Cannabis pollen.
FPSs from latter half of the Pleistocene show sites with
Cannabis pollen elsewhere in East Asia (Korea, 32ka, ESM
Table1 #10); as well as Kazakhstan (130ka, #152), South-
west Asia (Turkey, 111ka, #7; Black Sea near Turkey, 17ka,
#152; Caspian Sea near Iran, 14ka, #23; Georgia, 13ka,
#154; Syria, 11.9ka, #30); South Asia (India, 32.6ka, #11;
Sri Lanka, 18ka, #14; India, 12.8–11.9ka, #25, #26, #27,
#29); and Central Siberia (Altai, 16–15ka, #15, #17, #18).
One FPS in Bin 1 (ESM Table1, #9) conflicted with our
algorithm’s designation of a retting-site (Cannabis pol-
len 15% of TLP). That study reported CH pollen reaching
Fig. 1 Bin 1 (19.6Ma–11.6ka).
Age-weighted geographical
centroid for Cannabis data is
marked by a star. Background
base map by Natural Earth, free
open-source map data, https ://
www.natur alear thdat a.com
Vegetation History and Archaeobotany
1 3
61%, but it was clearly not a retting-site, because it occurred
34ka, long before agriculture began. The short-lived CH
pollen spike was superseded by Artemisia reaching 80% of
TLP, another unusual finding.
Bin 2 (11.55ka, Fig.2). During the early Holocene,
CH pollen consistent with wild-type Cannabis occurs
across Asia, from the Syrian and Anatolian steppes in the
west to the Liaoning plains in the east, and from the Altai
steppe in the north to the Central Highlands of India in the
south, even the Horton Plains of Sri Lanka. No CH pollen
consistent with cultivated Cannabis is detected in Bin 2.
However, several archaeological sites with Cannabis arti-
facts fall into Bin 2. The oldest sites are in Japan (Chiba,
10,000 b p, ESM Table1 #142) and China (Henan, 7,850
bp, #132). Somewhat younger artifacts are found in Japan
(Fukui, 7,200 bp, #144; Aomori, 5,900–4,300 bp, #146), and
in China (Hunan, 6,400–5,300 bp, #104; Gansu, 5,000 bp,
#109; and Inner Mongolia 5,000 bp, #134).
Bin 3 (4.50ka, Fig.3) During the late Holocene, CH
pollen consistent with wild-type Cannabis occurs across the
same range as Bin 2, excepting the loss of the Sri Lankan
site. Pollen consistent with cultivated Cannabis appears at 35
sites. At 11 of those sites, Humulus in a forested environment
gave way to land clearance and Cannabis cultivation, result-
ing in two symbols at the same sitewithin this time slice.
The oldest sites with pollen suggestingcultivated Canna-
bisare located in the lower Yangtze River basin, dating to
5,330 bp (#125) and 5,000 bp (a retting-site, with 15% TLP,
#130). In Northwest China, cultivated Cannabis is located in
Xinjiang (3,720 bp, #20; 2,600 bp, #129) and Qinghai (3,000
bp, #97). In East China, it appears in Shanxi (2,800 bp, #19).
Outside of China, pollen consistent with cultivated Cannabis
appears in Russia (3,700 bp, #155), Turkey (3,200 bp, #45;
2,300 bp, #153), Korea (3,150 bp, a retting-site, with 25% TLP,
#139), and India (2,500 bp, a retting-site, with 28% TLP, #71).
The oldest archaeological sites within this time slice are
located in Gansu (5,000–4,700 bp, #108, #110), Qinghai
(4,200–3,500 bp, #115, #116), Inner Mongolia (3,900–3,400
bp, #133), Shandong (3,600–3,000 bp, #124), and Xinjiang
(2,800–2,500 bp, #135, #136). Outside of China, relatively
old sites are found in central Korea (4,590–4,240 bp, #138),
the Ganges River basin in India (4,600–3,200 bp, #62–65),
Japan (3,500–3,000 bp, #147, #148), Nepal (2,400 bp, #76),
and the Russian Far East (2,500 bp, #79).
Extrapolating intotheOligocene
Next we deduced the location of Cannabis during the tem-
poral “missing link” between its divergence date (27.8Ma)
and oldest pollen (19.6Ma), using two sets of indirect data.
Bosboom etal. (2011) mapped an aridification zone aris-
ing at the Eocene–Oligocene boundary. The periphery of
their zone is demarcated by the central Tarim Basin, south-
ern Mongolia, and southeast of the Xining Basin. A best
approximation of this palaeogeographic zone was transferred
to a modern map in Fig.4. The oldest CH pollen consist-
ent with Cannabis (site #1) is located at the south-eastern
perimeter of the aridification zone (Fig.4).
Artemisia pollen during the late Eocene, Oligocene,
and early/mid Miocene, based on data from Miao etal.
(2011) is also mapped in Fig.4. The age-weighted centroid
for these data is located within Bosboom’s aridification
Fig. 2 Bin 2 (11.5–5ka). Back-
ground base map by Natural
Earth, free open-source map
data, https ://www.natur alear
thdat a.com/
Vegetation History and Archaeobotany
1 3
zone. The Artemisia centroid, at 38.621°N, 102.205°E, is
located 60km north of the Cannabis centroid shown in
Fig.1 (38.186°N, 101.910°E). This amazing proximity
is somewhat spurious, because the data set of Artemisia
and Cannabis pollen somewhat reflects the distribution
of palynologists, and accessibility to related strata, rather
than a theoretically complete distribution of pollen.
Discussion
The use of ecological proxies is an inferential method of
differentiating Cannabis and Humulus pollen (McPartland
etal. 2018). It offers a way to dissect Cannabis/Humulus
and other collective names assigned by palynologists, due
Fig. 3 Bin 3 (4.5–0ka). Back-
ground base map by Natural
Earth, free open-source map
data, https ://www.natur alear
thdat a.com/
Fig. 4 Black ellipse: aridifica-
tion zone arising at the Eocene–
Oligocene boundary (Bosboom
etal. 2011) transferred to a
modern map. Age-weighted
geographical centroid for
Artemisia data is marked by a
star. Background base map by
Natural Earth, free open-source
map data, https ://www.natur
alear thdat a.com/
Vegetation History and Archaeobotany
1 3
to the morphological similarities between Cannabis and
Humulus pollen. However, the method is inherently proba-
bilistic. The method also assumes that climatic require-
ments of modern Cannabis, Humulus, PAC, and ASP + can
be extrapolated to past populations—the nearest living
relative method (Mosbrugger and Utescher 1997).
Cannabis pollen has an age-weighted geographical cen-
troid located in the north-eastern Tibetan Plateau (Fig.1).
However, the evolution of Cannabis predates these data. We
applied Miao’s Artemisia data as a proxy for the location
of Cannabis during this temporal “missing link”. The age-
weighted geographical centroid for Artemisia pollen is also
located in the north-eastern Tibetan Plateau (Fig.4). Both
centroids fall within Bosboom’s aridification zone. The old-
est Cannabis pollen lies at the zone’s periphery. Thus, we
deduce the centre of origin of Cannabis, along with that
of Artemisia, as the north-eastern Tibetan Plateau, in the
general vicinity of Qinghai Lake.
Cannabis expanded westward from its centre of origin.
CH pollen consistent with Cannabis appeared in central
Russia (the cis-Ural region; ESM Table1, #156) by 1.5Ma.
Further west, a fossil seed (fruit) assigned to Cannabis in
Bulgaria dated to 7.3–5.3Ma (Palamarev 1982). Cannabis
expanded eastward from its centre of origin. By the end of
the Pleistocene, all regions of China except South Central
and Southwest China showed evidence of Cannabis.
FPSs in South Asia merit special attention: Humulus is
not native to India; H. lupulus was introduced as a culti-
gen by British colonists in the 1840s (Hooker 1890; Bakshi
and Atal 1985; Khuroo etal. 2007). The introduction of
non-native Humulus was also reported in Pakistan (Steward
1971), Nepal (Sood and Thakur 2015), and Burma (Kress
etal. 2003). Floras of Bangladesh and Thailand omit Humu-
lus (Khan and Halim 1990; Santisuk and Balslev 2015).
The absence of Humulus in South India provided a “beta
test” of our algorithm—all CH pollen in South Asia should
appear in pollen assemblages with a NAP/AP ratio 2, con-
sistent with Cannabis. In fact, several sites showed NAP/AP
ratios approaching 1:1 (ESM Table1, #42, #57, #59, #66,
#67). The CH pollen at these sites may be due to long-
distance transport, or represent small steppe communities
surrounded by forests. One South Asian study found CH
pollen in an assemblage with a NAP/AP ratio 0.5 (#71).
The CH percentage surged to 28%, in the presence of crop
pollen (Cerealia, Fagopyrum), which the algorithm identi-
fied as a hemp retting-site, as did the original authors.
South Asian studies that recorded “Cannabis” in pol-
len assemblages with high AP values may have misiden-
tified Celtis tree pollen. Notably, few South Asian FPSs
included Celtis (family Cannabaceae) in their pollen
diagrams. Three Celtis species are distributed in South
Asia, C. australis, C. tetrandra, and C. wightii (Watt
1889; Hooker 1890). Celtis pollen grains resemble those
of Cannabis—they are circular to elliptic, triporate with
circular pores surrounded by an annulus, a thin exine, and
smooth to verrucate surfaces. They have grain diameters
whose sizes fall into the range of Cannabis and Humulus
(see notes in ESM Table1, #60).
Whether Cannabis is native to South Asia, versus an
introduced species, is a long-standing debate (Watt 1889;
Hooker 1890). Experts still argue whether Himalayan Can-
nabis is indigenous (Zhou and Bartholomew 2003) or a natu-
ralized alien (Khuroo etal. 2007). We found pollen con-
sistent with Cannabis appearing in India by 32.6ka, which
suggests an indigenous species.
Cannabis in South Asia by 32.6ka begs the question of
when it actually arrived. Early floristic exchanges between
India and Asia were shaped by plate tectonics. As the Indian
plate migrated towards the Asian plate, it made a “glanc-
ing contact” with Sumatra 57Ma, followed by Burma, and
then a “hard collision” with Tibet 35Ma (Ali and Aitchison
2008). The glancing contact between continents resulted in
floristic exchanges during the Eocene (Bande 1992; Morley
and Dick 2003). The extant flora of India is often termed
Indo-Malayan. Cannabis arriving via Southeast Asia, during
the Eocene, seems unlikely. Southeast Asian FPSs are bereft
of CH pollen, and the Indo-Malayan exchange occurred
before Cannabis evolved.
The migrating Indian plate initiated uplift of the Tibet
plateau ca. 4035Ma, which was the primary cause of Bos-
boom’s aridification zone. The Tibet uplift, followed by the
Pamir uplift (35Ma) created a dispersal barrier between
Central Asia and India. Perhaps the biogeographical dis-
persal patterns of related plants, which we discuss below,
might reveal how Cannabis hurdled the dispersal barrier
into South Asia.
In contrast to the north-eastern Tibetan Plateau as the
centre of origin of Cannabis, Zhang etal. (2018b) offered
“low latitude” China as the centre of origin. Their estimate
was based on genetic variation in cpDNA sequences of 52
extant Cannabis accessions. Spatial analysis of molecular
variance (SAMOVA) determined the optimal number of
haplogroups to divide the accessions; the data best fit K = 3.
Phylogenetic tree topology placed the “L” (low latitude) hap-
logroup basal to the other haplogroups, whose accessions
came from Tibet (n = 7) and Yunnan (6), as well as Inner
Mongolia (3), Gansu (1), Guangxi (1), and Shandong (1).
Tibet and Yunnan embrace the south-eastern fringe of the
Tibetan Plateau, so our estimation of the Cannabis centre of
origin differs little from that of Zhang etal. (2018b).
The south-eastern fringe of the Tibetan Plateau, how-
ever, was the last sector uplifted, ca. 8Ma (Xing and Ree
2017). Prior to that, low altitude China was warmer and
wetter than today, and covered by subtropical broad-leaved
forests (Sun etal. 2011; Huang etal. 2016). We suggest
this ecosystem would not have driven the evolution of a
Vegetation History and Archaeobotany
1 3
steppe plant like Cannabis, according to the nearest living
relative method (Mosbrugger and Utescher 1997).
The south-eastern fringe of the Tibetan Plateau is
called the Henduan Mountains. Clarke and Merlin (2013)
proposed a Pleistocene glacial refugium in the Henduan
Mountains. Congruent with this, Zhang and colleagues
estimated a Cannabis crown date (divergence of the three
haplogroups) of 2.24Ma—the early Pleistocene. Given
this scenario, the “L” haplogroup should have expressed
the greatest π (nucleotide diversity). Instead, greatest π
was expressed by the “M” haplogroup, whose accessions
primarily came from Xinjiang (n = 5) and Tibet/Qing-
hai (n = 4). Disparity between stem age and crown age is
exampled by Ginkgo biloba, with uncertain range dynam-
ics arising from cpDNA sequences of extant relictual
populations (Hohmann etal. 2018).
Turning to cultivated Cannabis, the oldest pollen signal
identified by our methods dated to 5,330 bp (ESM Table1,
#125). At some sites dominated by AP pollen, we may
have misidentified pollen signals of Cannabis cultivation
as Humulus pollen. Pollen-based detection of early agri-
culture in densely forested sites often shares this conun-
drum (e.g. Tarasov etal. 2018).
Archaeological findings (seeds) predate 5,330 bp. Per-
haps the seeds were collected from wild-type Cannabis. A
Jōmon Culture site yielded the oldest seeds (ESM Table1
#142). The seeds were found with other edible nuts and
fruits, indicating food use. The Jōmon people made pot-
tery but did not farm—their economy was based on wild
resources and nut harvesting (Bleed and Matsui 2010).
Contrary to this wild-type hypothesis, however, photomi-
crographs of the Jōmon seeds do not show wild-type traits,
suggesting they were not only cultivated, but domesticated.
Serviceable fibre is not easily extracted from wild-
type growth, which branches excessively. Densely sown
crops, with minimal branching, yield the best fibre. The
clearest palynological signal of fibre use comes from
FPSs with Cannabis pollen 15% of TLP, indicative of a
retting-site. The oldest retting-site, dating to 5,000 bp, is
located in the Yangtze River delta (ESM Table1, #130).
The pollen identification is problematic, yet the authors
discuss hemp-retting as the source of their pollen surge,
as do other authors (TableS1, #71). Older non-palyno-
logical evidence—carbonized hemp fibres (excluded in
this study)—dates to 5,600 bp, in Henan (Zhang and Gao
1999). Intact rope and cloth dates to 5,000 bp, in the Yang-
tze River delta (Zhou 1980).
Archaeological evidence of ceremonial or drug use
dates to 2,700 bp, in Xinjiang (ESM Table1, #135, #136).
This interpretation is secured by the presence of processed
leaves and female flowering tops, stored in a leather bas-
ket, wooden bowl, or earthenware pot.
Cannabaceae biogeography
The geographic ranges of related species may help locate an
organism’s centre of origin (Crisci etal. 2003). The Humu-
lus centre of diversity lies in southwest China: H. lupulus
occurs in Sichuan; H. japonicus occurs in Sichuan, Yunnan,
Chongqing, Guangxi, and Guizhou; H. yunnanensis is lim-
ited to Yunnan (Zhou and Bartholomew 2003). Small (1978)
divided H. lupulus into five varieties, which collectively cir-
cumnutate the Northern Hemisphere at temperate latitudes.
Gray (1859) noted the Humulus connection between East
Asia and North America, foretelling the Bering land bridge
theory.
Pteroceltis tatarinowii, the only extant species of that
genus, is a tall canopy tree limited to China and Mongolia.
A phylogeographical reconstruction of 28 extant populations
identified southern China as the species’s centre of origin (Li
etal. 2012). However, fossils indicate that Pteroceltis is a
relictual lineage that once had a wider geographic range, and
similar to that of H. lupulus. Fossils of Pteroceltis tertiaria
were found in Germany, and fossils of Pteroceltis knowltonii
were found in the USA (Manchester etal. 2009).
Celtis is the largest genus in the Cannabaceae, with about
70 species, and 13 grow in China. Celtis also has the larg-
est native range in the Cannabaceae, spanning temperate
as well as tropical latitudes. In the Northern Hemisphere,
Gray (1859) included Celtis in his proto-Bering land bridge
theory. In the Southern Hemisphere, Celtis occurs in South
America, Africa, and Australia (Stevens 2008). The oldest
Celtis fossils (of C. aspera, 64–56Ma) have been found in
the Russian Far East and the western USA (Manchester etal.
2002). This hints at an East Asian origin for the genus.
Trema and Parasponia are sometimes synonymized; a
molecular study found both Trema and Parasponia para-
phyletic, with no clear basal lineages (Yesson etal. 2004).
Twelve Trema species grow in subtropical and tropical
regions, in southern China, India, Southeast Asia, Africa,
and Central America. China is the Trema centre of diversity,
with eight species growing there. Parasponia species do not
occupy continental Asia; they are found in Indonesia, Papua
New Guinea, Philippines, northern Australia, and some Mel-
anesian and Polynesian islands.
Aphananthe species occur in China, Japan, Korea, India,
Sri Lanka, Southeast Asia (including Philippines and Papua
New Guinea), Mexico, Madagascar, and Australia. Fossils
indicate a wider distribution, with finds in western Siberia,
Germany, and the USA (Yang etal. 2017). Phylogenetic
studies place Aphananthe basal to the rest of the Canna-
baceae, hence it is the oldest genus (Yang etal. 2013; Zhang
etal. 2018a). A fossil from Germany, Aphananthe cretacea,
dates to 66–72.1Ma (Knobloch and Mai 1986).
Yang etal. (2017) reconstructed the biogeography of
Aphananthe using DNA sequences and other molecular
Vegetation History and Archaeobotany
1 3
methods. They identified East Asia as the ancestral area
of extant Aphananthe species. Dispersal took Aphananthe
across the Bering land bridge into North America around
19.1Ma, and into South Asia by 18.1Ma. A route from East
Asia to South Asia was not delineated. A. cuspidata occupies
contiguous areas spanning East Asia and South Asia—Yun-
nan, Burma, and India—so that is the likely route.
In summary, most Cannabaceae genera have origins in
East Asia. The ancestral distribution of Cannabis resembles
that of H. lupulus, except Cannabis dispersed to South Asia,
and H. lupulus crossed the Bering land bridge. We propose
that the progenitor of Cannabis dispersed from East Asia to
the north-eastern Tibetan Plateau, where it underwent para-
patric speciation in Bosboom’s aridification zone, amidst
Asia’s first steppe community.
Cannabis dispersed from the Tibetan Plateau, first to
the west (Russia and Europe) and then to the east (China).
By the end of the Pleistocene, Cannabis spread through-
out Asia, except for Southeast Asia. Thus, wild-type Can-
nabis was available for people across Eurasia to bring into
cultivation and domesticate. Several sites in south-eastern
Europe, mostly associated with the Yamnaya Culture, sug-
gest autochthonous domestication in Europe (Clarke and
Merlin 2013; Long etal. 2017; McPartland and Hegman
2018). Vavilov (1926) would have agreed, “it is probable
that the cultivation of hemp arose simultaneously and inde-
pendently in several places”.
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... 8,9 The putative center of origin of the genus Cannabis has been widely speculated in Central Asia. 10,11 Based on subfossil pollen and archaeobotanical studies, McPartland et al. 11 deduced the northeast of the Tibetan plateau in the vicinity of Qinghai Lake as the center of origin for Cannabis, over 19.6 Ma. Furthermore, molecular studies of DNA chloroplast-specific regions estimated that Cannabis has diverged from its relative, Humulus between 27.8 Ma (Oligocene) 12 (mid-Miocene). ...
... 8,9 The putative center of origin of the genus Cannabis has been widely speculated in Central Asia. 10,11 Based on subfossil pollen and archaeobotanical studies, McPartland et al. 11 deduced the northeast of the Tibetan plateau in the vicinity of Qinghai Lake as the center of origin for Cannabis, over 19.6 Ma. Furthermore, molecular studies of DNA chloroplast-specific regions estimated that Cannabis has diverged from its relative, Humulus between 27.8 Ma (Oligocene) 12 (mid-Miocene). ...
... 13 The Cannabis spread from the Tibetan plateau, first to the west (Russia and Europe by 6 Ma), then to the east (eastern China by 1.2 Ma), and by the end of Pleistocene to the rest of Asia (except the southeast). 11 The evidence for human's use of Cannabis came from archeological sites of China, Japan, and Europe since the Neolithic period, 14,15 but the earliest human use as a food source may date back to 10,000 BP in Japan. 11,16,17 Evidence in the form of cord-impressed ceramics of Cannabis use as fiber plant is possibly as early as 1200 years ago. ...
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Background: Cannabis has been cultivated and used for centuries in the north Moroccan Rif (local name is kif). However, its history is poorly known and the date of its first introduction and dispersal in Morocco is still difficult to be precise. Aim: The purpose of the present work is to review the literature on the origin, history, and cultivation of Cannabis in Morocco, as well as data on the morphological, genetic, and phytochemical characteristics of local cultivated varieties. Discussion: Considering the importance of preserving the fragile environment of the Rif and the future development of the Moroccan medical Cannabis market, which will require authentication of the raw material, the use of local strains which are well adapted to the particular environment of the Rif is highly recommended. However, there is no document that summarizes and clarifies the nomenclature and the characteristics of local Moroccan Cannabis. In addition, the recent adoption by Rif growers of improved hybrid cultivars is obliterating the traits and peculiarities of Moroccan Cannabis through genetic introgression. Conclusion: Summarizing and discussing the data from the literature on the characteristics of local Moroccan Cannabis varieties may be useful for their identification and the localization of the areas of the Rif region where their cultivation is still practiced.
... Cannabis is considered to be monotypic (occurs as a single species), but arguments for its polytypic nature also exist [2]. The origin point of Cannabis is believed to be in Asia, with some evidence pointing to Central Asia [3], while other evidence points to the lower latitudes of the Asian continent [4] as the likely point of origin. However, it was in East Asia where humans first domesticated Cannabis more than 12,000 years ago [5]. ...
... Several locations within the Central Asia region have been proposed to be the likely origin points of Cannabis [38]. Specifically, a study on the Cannabis subfossil pollen deduced that the plant originated in the Qinghai Lake area of Northeastern Tibet [3]. Being the biodiversity center of both Cannabis and Humulus [39], the Central Asia region is considered as the most likely origin point of the two plants. ...
... This implies that true wild-type Cannabis, through which true ancestry could be traced, does not exist [5,38]. Second, the fossilized pollen grains of Cannabis are indistinguishable from those of Humulus lupulus [3,40], making it difficult to correctly identify and use fossilized pollen grains to ascertain ancestry of the two species. ...
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Cannabis sativa L. is an illegal plant in many countries. The worldwide criminalization of the plant has for many years limited its research. Consequently, understanding the full scope of its benefits and harm became limited too. However, in recent years the world has witnessed an increased pace in legalization and decriminalization of C. sativa. This has prompted an increase in scientific studies on various aspects of the plant’s growth, development, and use. This review brings together the historical and current information about the plant’s relationship with mankind. We highlight the important aspects of C. sativa classification and identification, carefully analyzing the supporting arguments for both monotypic (single species) and polytypic (multiple species) perspectives. The review also identifies recent studies on suitable conditions and methods for C. sativa propagation as well as highlighting the diverse uses of the plant. Specifically, we describe the beneficial and harmful effects of the prominent phytocannabinoids and provide status of the studies on heterologous synthesis of phytocannabinoids in different biological systems. With a historical view on C. sativa legality, the review also provides an up-to-date worldwide standpoint on its regulation. Finally, we present a summary of the studies on genome editing and suggest areas for future research.
... The macrofossil record of Cannabis is relatively scarce and consists of only a few leaf and fruit/seed impressions with ages ranging between the Oligocene and the late Miocene (McPartland et al., 2019). However, microfossils, specifically pollen, are abundant and widespread and have commonly been utilized to reliably reconstruct the history of Cannabis. ...
... In spite of this, they favoured the mid-Oligocene age for the origin of Cannabis on the NE Tibetan Plateau (Fig. 4), assuming that, as demonstrated by the presence of Artemisia and other steppe elements, the region was covered by this type of vegetation, which would have been particularly well suited for the development of Cannabis. A previous study using Bayesian calibration estimated the divergence between Cannabis and Humulus to have occurred 21 Ma (Zerega et al., 2005), which is closer to the age (19.6 Ma) of the first fossil pollen evidence mentioned above (McPartland et al., 2019). ...
... According to pollen and seed fossil records, Cannabis would have experienced some expansion from its centre of origin to Europe and East Asia before the onset of human evolution (Fig. 4). The suggested dispersal agents are water (hydrochory) and animals (zoochory) (McPartland, 2018;McPartland et al., 2019). The first expansions occurred to the west (eastern Europe) and the east (north-eastern China) during the Miocene-Pliocene. ...
Preprint
Cannabis is among the oldest human domesticates and has been subjected to intensive artificial (human-mediated) selection throughout history to create a wide array of varieties and biotypes for diverse uses, including fibre, food, biofuel, medicine and drugs. This paper briefly reviews the available literature on the taxonomy, evolutionary origin and domestication of this plant, as well as its worldwide dispersal, in both its wild and cultivated forms. Emphasis is placed on Europe and especially on the Iberian Peninsula. Today, it is accepted that Cannabis is a monospecific genus with two subspecies, C. sativa subsp. sativa and C. sativa subsp. indica, originating in Europe and Asia, respectively, by allopatric differentiation after geographic isolation fostered by Pleistocene glacial-interglacial cycles. Palynological and phylogeographic evidence situates the Cannabis ancestor on the NE Tibetan Plateau during the mid-Oligocene. The timing and place of domestication is still a matter of debate between contrasting views that defend single or multiple Neolithic domestication centres situated in different parts of the Eurasian supercontinent, notably central/southeastern China and the Caucasus region. Recent meta-analyses have suggested that wild Cannabis may have already been spread across Europe in the Pleistocene, and its domestication could have occurred during the European Copper/Bronze ages. According to the available reviews and meta-analyses, pre-anthropic dispersal of Cannabis into the Iberian Peninsula seems to have occurred only in postglacial times, and the earlier signs of cultivation date to the Early Medieval Ages. However, the palynological and archaeological evidence used to date is insufficient for a sound assessment, and the development of thorough Iberian databases to address further meta-analysis is essential for more robust conclusions. Some clues are provided for these achievements to be fulfilled.
... The macrofossil record of Cannabis is relatively scarce and consists of only a few leaf and fruit/seed impressions with ages ranging between the Oligocene and the late Miocene (McPartland et al. 2019). However, microfossils, specifically pollen, are abundant and widespread and have commonly been utilized to reliably reconstruct the history of Cannabis. ...
... According to pollen and seed fossil records, Cannabis would have experienced some expansion from its center of origin to Europe and East Asia before the onset of human evolution (Fig. 4). The suggested dispersal agents are water (hydrochory) and animals (zoochory) (McPartland 2018;McPartland et al. 2019). The first expansions occurred to the west (eastern Europe) and the east (NE China) during the Miocene-Pliocene. ...
... Indeed, when flowering male hemp plants are soaked in a retting pond to separate the fibers from the stalk, large quantities of pollen settle into pond sediments. In these situations, the percentages of Cannabis pollen in sediments may reach 80-90% of the total, but percentages over 15% or 25% have been considered sufficient to infer hemp retting (Peglar 1993;Mercuri et al. 2002;Demske et al. 2016;McPartland et al. 2019). The anemophylous pollen of Cannabis may be transported long distances; therefore, the finding of a few grains or their scattered occurrence throughout a stratigraphic section is not necessarily evidence for the local presence of the parent plant. ...
Preprint
Cannabis is among the oldest human domesticates and has been subjected to intensive artificial (human-mediated) selection through history, to create a wide array of varieties and biotypes for a diversity or uses, including fiber, food, biofuel, medicine and drugs, among others. This paper briefly reviews the available literature on the taxonomy, the evolutionary origin and the domestication of this plant, as well as its worldwide dispersal, either in its wild and cultivated forms. Emphasis is placed on Europe and especially on the Iberian Peninsula, which is the main target of this study. Today it is accepted that Cannabis is a monospecific genus with two subspecies, C. sativa subsp. sativa and C. sativa subsp. indica, originated in Europe and Asia, respectively, by allopatric differentiation after geographical isolation fostered by Pleistocene glacial-interglacial cycles. Palynological and phylogeographical evidence situate the Cannabis ancestor in the NE Tibetan Plateau during the Oligocene (ca. 28 Ma). The timing and place of domestication is still a matter of debate between contrasting views that defend single or multiple domestication centers, situated in different parts of the Eurasian supercontinent, notably central/southeastern China and the Caucasus region. Recent meta-analyses suggest that wild Cannabis may have been spread across Europe already in the Pleistocene (ca. 1 Ma), and its domestication could have been occurred during the European Copper/Bronze ages (7-5 kyr BP). According to the available reviews and meta-analyses, pre-anthropic dispersal of Cannabis into the Iberian Peninsula seems to have been occurred only in post-glacial times (18.5-15 kyr BP) and the earlier signs of cultivation date to the Early Medieval Ages (ca. 600 CE). However, the palynological and archaeological evidence used to date is insufficient for a sound assessment and the development of thorough Iberian databases to address further meta-analysis are essential for more robust conclusions. Some clues are provided for these achievements to be fulfilled.
... Scientific studies consider that cannabis was originally from Asia and that, from there, it was domesticated and disseminated around the world due to its versatility in terms of adaptation to the climate and in terms of potential uses [3,4]. It is important to understand whether the exponential growth of medical cannabis production in several Western countries that have already legalized its use and production is sustainable given that in many of these countries the plant is not endemic. ...
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Introduction: Cannabis has recently gained a medical status in several countries in the world. Its production for medical purposes should be analysed based on the three pillars of sustainability, taking into account the country in which it is located. Methods: literary research was conducted through scientific databases and grey literature, such as institutional websites. Results: Studies from the United States of America and Australia on the socioeconomic and environmental impacts of medical cannabis production were consulted, showing that this crop can be socially and economically beneficial in the place where it is executed but, in environmental terms, there is still a long way to go to understand the impacts on the consumption of energy, water, pesticides, fertilizers and waste waters compliance. Conclusions: The introduction of new non-autochthonous species should be accompanied by studies assessing their impact on the production site. The production of medical cannabis has been increasing and it is imperative to study its impacts in order to be able to implement measures to mitigate potential negative effects.
... Originally from Asia, C. sativa grows vigorously outdoors in a variety of latitudes and climates around the world (Long et al., 2017;McPartland et al., 2018McPartland et al., , 2019. However, in countries where the plant is a controlled substance, C. sativa growers are often restricted to indoor cultivation for a variety of reasons including: climatic conditions may not suitable for all-year, outdoor growing (e.g., Canada), regulations that restrict outdoor cultivation (e.g., Greece, New Zealand, United Kingdom), or a combination of these reasons (Misuse of Drugs (Amendments) (Cannabis Licence Fees) (England, Wales and Scotland) Regulations, 2018; Brown and Blackburn, 1987; Misuse of Drugs (Medicinal Cannabis) Amendment Bill, 2018; Folina et al., 2019). ...
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Cannabis sativa L. is an annual, short-day plant, such that long-day lighting promotes vegetative growth while short-day lighting induces flowering. To date, there has been no substantial investigation on how the switch between these photoperiods influences yield of C. sativa despite the tight correlation that plant size and floral biomass have with the timing of photoperiod switches in indoor growing facilities worldwide. Moreover, there are only casual predictions around how the timing of the photoperiodic switch may affect the production of secondary metabolites, like cannabinoids. Here we use a meta-analytic approach to determine when growers should switch photoperiods to optimize C. sativa floral biomass and cannabinoid content. To this end, we searched through ISI Web of Science for peer-reviewed publications of C. sativa that reported experimental photoperiod durations and results containing cannabinoid concentrations and/or floral biomass, then from 26 studies, we estimated the relationship between photoperiod and yield using quantile regression. Floral biomass was maximized when the long daylength photoperiod was minimized (i.e., 14 days), while THC and CBD potency was maximized under long day length photoperiod for ~42 and 49–50 days, respectively. Our work reveals a yield trade-off in C. sativa between cannabinoid concentration and floral biomass where more time spent under long-day lighting maximizes cannabinoid content and less time spent under long-day lighting maximizes floral biomass. Growers should carefully consider the length of long-day lighting exposure as it can be used as a tool to maximize desired yield outcomes.
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The reconstruction of human impact is pivotal in palaeoecological studies, as humans are among the most important drivers of Holocene vegetation and ecosystem change. Nevertheless, separating the anthropogenic footprint on vegetation dynamics from the impact of climate and other environmental factors (disturbances such as fire, erosion, floods, landslides, avalanches, volcanic eruptions) is a challenging and still largely open issue. For this purpose, palynologists mostly rely on cultural indicator pollen types and related indices that consist of sums or ratios of these pollen types. However, the high environmental and biogeographical specificity of cultural indicator plants hinders the application of the currently available indices to wide geographical settings. Furthermore, the achievable taxonomic resolution of cultural indicator pollen types may hamper their indicative capacity. In this study, we propose the agricultural land use probability (LUP) index, a novel approach to quantify human impact intensity on European ecosystems based on cultural indicator pollen types. From the ‘classic’ cultural indicators, we construct the LUP index by selecting those with the best indicator capacity based on bioindication criteria. We first train the LUP index using twenty palynological sequences along a broad environmental gradient, spanning from treeless alpine to subtropical mediterranean evergreen plant communities. We then validate the LUP index using independent pollen datasets and archaeological proxies. Finally, we discuss the suitability of the selected pollen types and the potential of the LUP index for quantifying Holocene human impact in Europe, concluding that careful application of the LUP index may significantly contribute to refining pollen-based land-use reconstructions.
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Cannabis is among the oldest human domesticates and has been subjected to intensive artificial (human-mediated) selection throughout history to create a wide array of varieties and biotypes for diverse uses, including fiber, food, biofuel, medicine and drugs. This paper briefly reviews the available literature on the taxonomy, evolutionary origin and domestication of this plant, as well as its worldwide dispersal, in both its wild and cultivated forms. Emphasis is placed on Europe and especially on the Iberian Peninsula. Today, it is accepted that Cannabis is a monospecific genus with two subspecies, C. sativa subsp. sativa and C. sativa subsp. indica, originating in Europe and Asia, respectively, by allopatric differentiation after geographic isolation fostered by Pleistocene glacial-interglacial cycles. Palynological and phylogeographic evidence situates the Cannabis ancestor on the NE Tibetan Plateau during the mid-Oligocene. The timing and place of domestication is still a matter of debate between contrasting views that defend single or multiple Neolithic domestication centers situated in different parts of the Eurasian supercontinent, notably central/southeastern China and the Caucasus region. Recent meta-analyses have suggested that wild Cannabis may have already been spread across Europe in the Pleistocene, and its domestication could have occurred during the European Copper/Bronze ages. According to the available reviews and meta-analyses, pre-anthropic dispersal of Cannabis into the Iberian Peninsula seems to have occurred only in postglacial times, and the earlier signs of cultivation date to the Early Medieval Ages. However, the palynological and archaeological evidence used to date is insufficient for a sound assessment, and the development of thorough Iberian databases to address further meta-analysis is essential for more robust conclusions. Some clues are provided for these achievements to be fulfilled.
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Cannabis: Evolution and Ethnobotany is a comprehensive, interdisciplinary exploration of the natural origins and early evolution of this famous plant, highlighting its historic role in the development of human societies. Cannabis has long been prized for the strong and durable fiber in its stalks, its edible and oil-rich seeds, and the psychoactive and medicinal compounds produced by its female flowers. The culturally valuable and often irreplaceable goods derived from cannabis deeply influenced the commercial, medical, ritual, and religious practices of cultures throughout the ages, and human desire for these commodities directed the evolution of the plant toward its contemporary varieties. As interest in cannabis grows and public debate over its many uses rises, this book will help us understand why humanity continues to rely on this plant and adapts it to suit our needs.
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Cannabis is one of the most important industrial crops distributed worldwide. However, the phylogeographic structure and domestication knowledge of this crop remains poorly understood. In this study, sequence variations of five chloroplast DNA (cpDNA) regions were investigated to address these questions. For the 645 individuals from 52 Cannabis accessions sampled (25 wild populations and 27 domesticated populations or cultivars), three haplogroups (Haplogroup H, M, L) were identified and these lineages exhibited distinct high-middle-low latitudinal gradients distribution pattern. This pattern can most likely be explained as a consequence of climatic heterogeneity and geographical isolation. Therefore, we examined the correlations between genetic distances and geographical distances, and tested whether the climatic factors are correlated with the cpDNA haplogroup frequencies of populations. The “isolation-by-distance” models were detected for the phylogeographic structure, and the day-length was found to be the most important factor (among 20 BioClim factors) that influenced the population structures. Considering the distinctive phylogeographic structures and no reproductive isolation among members of these lineages, we recommend that Cannabis be recognized as a monotypic genus typified by Cannabis sativa L., containing three subspecies: subsp. sativa, subsp. Indica, and subsp. ruderalis. Within each haplogroup which possesses a relatively independent distribution region, the wild and domesticated populations shared the most common haplotypes, indicating that there are multiregional origins for the domesticated crop. Contrast to the prevalent Central-Asia-Origin hypothesis of C. saltiva, molecular evidence reveals for the first time that the low latitude haplogroup (Haplogroup L) is the earliest divergent lineage, implying that Cannabis is probably originated in low latitude region. © 2018 Zhang, Chen, Guo, Trindade, Salentijn, Guo, Guo, Xu and Yang.
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Dispersal is a fundamental ecological process, yet demonstrating the occurrence and importance of long‐distance dispersal (LDD) remains difficult, having rarely been examined for widespread, non‐coastal plants. To address this issue, we integrated phylogenetic, molecular dating, biogeographical, ecological, seed biology and oceanographic data for the inland Urticaceae. We found that Urticaceae originated in Eurasia c. 69 Ma, followed by ≥ 92 LDD events between landmasses. Under experimental conditions, seeds of many Urticaceae floated for > 220 days, and remained viable after 10 months in seawater, long enough for most detected LDD events, according to oceanographic current modelling. Ecological traits analyses indicated that preferences for disturbed habitats might facilitate LDD. Nearly half of all LDD events involved dioecious taxa, so population establishment in dioecious Urticaceae requires multiple seeds, or occasional selfing. Our work shows that seawater LDD played an important role in shaping the geographical distributions of Urticaceae, providing empirical evidence for Darwin's transoceanic dispersal hypothesis.
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Dispersal is a fundamental ecological process, yet demonstrating the occurrence and importance of long‐distance dispersal (LDD) remains difficult, having rarely been examined for widespread, non‐coastal plants. To address this issue, we integrated phylogenetic, molecular dating, biogeographical, ecological, seed biology and oceanographic data for the inland Urticaceae. We found that Urticaceae originated in Eurasia c. 69 Ma, followed by ≥ 92 LDD events between landmasses. Under experimental conditions, seeds of many Urticaceae floated for > 220 days, and remained viable after 10 months in seawater, long enough for most detected LDD events, according to oceanographic current modelling. Ecological traits analyses indicated that preferences for disturbed habitats might facilitate LDD. Nearly half of all LDD events involved dioecious taxa, so population establishment in dioecious Urticaceae requires multiple seeds, or occasional selfing. Our work shows that seawater LDD played an important role in shaping the geographical distributions of Urticaceae, providing empirical evidence for Darwin's transoceanic dispersal hypothesis.