2006 Seed Size Increase as a Marker of Domestication in Squash

Introduction
Among the most basic questions surrounding the origin of
any plant or animal domesticate are the identity of its wild
ancestor and the temporal, spatial, and cultural context of
its initial domestication. Inherent in these questions of where
and when a domesticate first emerged is the issue of whether
the domestication was a single isolated development, or if
multiple independent domestications of a species occurred
at different times in different places. The geographical extent
and degree of internal partitioning of the range of a wild
ancestor obviously is an important factor in whether single
or multiple domestications take place. A single origin, for
example, has long been proposed for a number of the Near
Eastern cereals whose wild ancestors had quite restricted and
internally unpartitioned geographical ranges (Zohary 1996).
Contrary to Lentz’s recent proposition (Lentz et al. 2001: 375),
such single origins for some cereal domesticates should
not be considered as evidence that plant domestication in
general involves single domestication events followed by
diffusion. Multiple domestications are always a possibility
where wild plant or animal progenitor populations extend
across a broad and varied geographical range.
In the Americas, Cucurbita pepo squash (pumpkins, acorn,
and summer varieties), is, along with Chenopodium (Chapter 4),
one of the best-documented species to have been domesticated
more than once from wild ancestor populations having
a broad geographical range. More than 10 different taxa
of wild Cucurbita gourds have overlapping geographical
distributions that today extend from northern South America
up into the mid-latitude eastern United States (Nee 1990). A
half-dozen domesticated squashes were developed out of
these wild Cucurbita taxa (i.e., C. maxima, C. moschata,
C. ficafolia, C. argyrosperma, C. equadorensis, C. pepo: Robinson
and Decker-Walters 1997; Piperno and Stothert 2003; Sanjur
et al. 2002, 2004). Among these, Cucurbita pepo was independently
domesticated twice—first in south central Mexico about
10,000 years ago and then again, on the basis of currently
available archaeological evidence, in the mid-latitude eastern
woodlands of North America by about 5,000 years ago (Smith
1997, 2000, 2002). In both Mexico and the eastern United
States, this independent domestication of C. pepo squash is
indicated by clear changes in the morphology of C. pepo
C HAPTER 3
Seed Size Increase as a Marker of Domestication in Squash
(Cucurbita pepo)
BRUCE D. SMITH
recovered from human habitation layers in archaeological
sites. These morphological changes distinguish the early
domesticated crop plants from all of their related wild taxa,
including their direct wild ancestors, and they have also
been linked to a specific set of causative human behaviors—
the deliberate and sustained planting of stored seed stock.
Morphological Markers of Domestication
In the 1960s and 1970s, Harlan, de Wet, and Price published
a series of articles that outlined a clear set of morphological
criteria for distinguishing between wild and domesticated
seed plants based on changes in reproductive propagules
resulting from the storage, planting, and harvesting of seed
stock over a number of years (Harlan and de Wet 1965;
Harlan et al. 1973; de Wet and Harlan 1975). These morphological
changes, which reflect responses by the now managed
plants to new sets of selective pressures, both in the seedbed
and at harvest, are automatic and independent of any
deliberate or directed selection on the part of humans; they
have collectively been termed “the adaptive syndrome
of domestication” (Chapter 1, 2; Smith 1998, 2002). Those
plants with seeds tightly clustered and tightly held at the
terminal ends of their stalks, for example, would have a
selective advantage at harvest in that they would be more
likely to be seen and successfully collected and thus to
contribute to next year’s planting. Similarly, seeds that sprout
quickly because of reduced germination dormancy (thinner
seed coat—see Chapter 4) and that grow rapidly (greater
stored start-up energy, larger seed) in seedbeds would have
a selective advantage in terms of competing for sunlight and
surviving to be harvested.
Unfortunately, most of the morphological changes in seed
plants identified by Harlan and others as resulting from
deliberate human planting and harvesting are difficult to
document in archaeobotanical assemblages. One of the most
obvious, and most archaeologically visible, of these changes
that mark initial domestication is an increase in seed size in
response to seedbed selective pressures.
In order to use seed size as a criterion for differentiating
between the seeds of wild and domesticated C. pepo squash,
a comprehensive standard, or baseline, of comparison of seed
measurements for wild Cucurbita taxa is needed. Figures 3.1
SEED SIZE INCREASE OF SQUASH 25

10
8
6
4
Phillips Spring
a
2
0
6 7 8 9 10 11 12 13 14
10
8
6
4
Page-Ladson
b
2
0
6 7 8 9 10 11 12 13 14
20
15
10
5
C. pep ssp. ovifera var. ozarkana
c 0
6 7 8 9 10 11 12 13 14
10
8
6
4
C. pepo ssp. ovifera var. texana
d
2
0
6 7 8 9 10 11 12 13 14
10
8
6
4
C. fraterna
e
2
0
6 7 8 9 10 11 12 13 14
Seed Length (mm)
FIGURE 3.1 The size of Cucurbita pepo seeds from
archaeological and paleontological sites in North America
compared to three taxa of modern wild C. pepo gourds.
(a) Phillip Spring (n = 45, mean = 10.5); (b) Page-Ladson
(n = 35, mean = 9.9); (c) C. pepo ssp. ovifera var. ozarkana
(n = 100, mean = 9.2); (d) C. pepo ssp. ovifera var. texana
(n = 42, mean = 8.9); (e) C. pepo ssp. ovifera var. fraterna
(n = 13, mean = 7.9).
and 3.2 provide such a general wild Cucurbita gourd seed
profile. More than 700 seeds from 63 separate accessions,
representing 12 modern species, subspecies, or varieties of
wild Cucurbita gourds were measured. With the exception
of C. pedatifolia and C. galeottii, all known North American
(Mexican and U.S.) wild Cucurbita species are represented in
Figures 3.1 and 3.2 (see Nee 1990: 58). In addition to the 12
modern taxa included in Figures 3.1 and 3.2, seed length
information is also presented for the Page-Ladson seed
assemblage (Figure 3.1b), a collection of late Pleistocene seeds
of a wild Cucurbita gourd recovered from American Mastodon
(Mammut americanum) dung deposits in north Florida
(Newsom et al. 1993). Of the more than 700 modern seeds
measured, the smallest was 7.0 mm long (Figures 3.1c and e,
Figure 3.2g), while the largest was 11.9 mm in length
(Figure 3.2b). The largest seeds in 10 of the 13 different taxa
exceeded 10 mm in length, but none were larger than 12 mm
long (only 6 of the 717 seeds were longer than 11 mm and
only 1 measured more than 11.5 mm in length). These
maximum-length values provide a strong basis for defining
the upper size-range ceiling for seeds of North American
wild Cucurbita gourds at 11–12 mm in length.
At the species level of comparison, the three C. pepo taxa
listed in Figure 3.1c–e (C. pepo ssp. ovifera var. ozarkana,
C. pepo ssp. ovifera var. texana, C. pepo ssp. fraterna) provide
26 ARCHAEOLOGY AND PLANT DOMESTICATION
10
8
6
4
2
a 0
10
8
6
4
2
b 0
10
8
6
4
2
c 0
10
8
6
4
2
d 0
10
8
6
4
2
e 0
f
10
8
6
4
2
0
Level D
Level C
Level B
6 7 8 9 10 11 12 13 14
6 7 8 9 10 11 12 13 14
C. okeechobeenis
C. martinezii
6 7 8 9 10 11 12 13 14
C. gracilior
C. cordata
Guilá Naquitz
C. palmata
C. okeechobeensis
C. martinezii
C. gracilior
C. cordata
6 7 8 9 10 11 12 13 14
C. argyrosperma ssp. sororia
6 7 8 9 10 11 12 13 14
C. lundelliana
6 7 8 9 10 11 12 13 14
10
8
6
4
C. foetidissima
C. digitata
C. foetidissima
C. digitata
2
g 0
6 7 8 9 10 11 12 13 14
Seed Length (mm)
FIGURE 3.2 The size of Cucurbita pepo seeds from Guilá
Naquitz compared to six taxa of modern wild Cucurbita
gourds. (a) Guilá Naquitz, Levels B, C, and D (n = 15);
(b) C. palmata (n = 75, mean = 10.2); (c) C. okeechobeensis
(n = 20, mean = 9.9) and C. martinezii (n = 46, mean = 9.9);
(d) C. gracilior (n = 10, mean = 10.7) and C. cordata (n = 10,
mean = 9.5); (e) C. argyrosperma ssp. sororia (n = 75,
mean = 9.7); (f) C. lundelliana (n = 50, mean = 9.0);
(g) C. foetidissima (n = 55, mean = 8.7) and C. digitata
(n = 20, mean = 8.8).
a smaller, taxonomically tighter, reference class, with their
upper limit for seed length (ca. 11 mm) representing a more
closely drawn wild/domesticated boundary line than the
12-mm seed length ceiling derived from the 13-taxa
reference class. These three modern taxa of wild, or “freeliving,”
Cucurbita gourds actually represent an even tighter,
more focused reference class in that recent genetic research
(Sanjur et al. 2002, 2004) has identified them as not
only closely related to each other, but also as a group
representing the present-day descendants of the wild
progenitor populations of Cucurbita gourds that gave rise to
the “eastern” lineage of domesticated squash (C. pepo. ssp.
ovifera) about 5,000 years ago. A previous study (Decker-
Walters et al. 1993) had identified one of these three—the
wild Ozark gourd (C. pepo ssp. ovifera var. ozarkana)—as
the progenitor of the C. pepo ssp. ovifera domesticate

Huitzo
Etla
ETLA SUBVALLEY
Zaachila
Rio Aloyac
Zimatlan
Oaxaca
Ocollán
LOCATION OF VALLEY OF OAXACA
Abasolo
Tlacolula
Rio Salado
ZAACHILA-ZIMATLAN SUBVALLEY
FIGURE 3.3 The location of Guilá Naquitz Cave in the
Valley of Oaxaca (after Flannery 1986: Figure 3.1).
lineage, but the progenitor pool and the geographical range
within which domestication occurred has now been
expanded. Unfortunately, present-day populations of the
wild ancestor of the Mexican domesticated C. pepo squash
lineage have yet to be located. Since the seeds of modern
cultivars of the “eastern” lineage of C. pepo are smaller than
those of the Mexican lineage, this size difference could also
have existed, some scholars have suggested, in the wild
ancestor populations (Robinson and Decker-Walters 1997: 7).
As a result, although 11 mm represents a good minimum
length boundary for identifying domesticated C. pepo seeds
in eastern United States archaeological contexts, the larger
reference class value of 12 mm provides a more prudent
minimum seed-length boundary for the designation of domesticated
C. pepo in Mexico, at least until the wild progenitor
of the Mexican C. pepo lineage has been identified.
Given these minimum seed-length values of 11 mm and
12 mm for establishing the initial appearance of domesticated
C. pepo squash in the eastern United States and Mexico, we
can turn to consideration of the archaeological sites and
human habitation layers that have yielded the oldest seeds
exceeding these seed-length thresholds.
The Cucurbita pepo Seed and Peduncle
Assemblage of Guilá Naquitz Cave
TLACOLULA SUBVALLEY
Guilá Naquitz
Mitla
0 5 10
km
Situated in a small tributary canyon of the Rio Mitla in the
Valley of Oaxaca (Figure 3.3), Guilá Naquitz Cave was
excavated by Kent Flannery in 1966 (Flannery 1986). The
small 8- by 10-m cave opening at the base of the canyon wall
was found to contain a 20-cm-thick habitation layer (Zone
A) dating to AD 620–740, and below this, a number of much
+
N
FIGURE 3.4 Cucurbita pepo seeds from Guilá Naquitz Cave
yielding AMS dates in the Early Archaic. (a) seed from Square
C11, Zone B2 (INAH 5) measuring 12.5 mm in length and
yielding an AMS radiocarbon date of 6475 cal. BC; (b) seed
from Square E9, Zone C (INAH 14) measuring 13.8 mm in
length and yielding an AMS radiocarbon date of 7975 cal
BC; (c) seed from Square E11, Zone B1 (INAH 23) measuring
13.2 mm in length and yielding an AMS radiocarbon date of
8025 cal. BC; (d) Seed from Square C11, Zone B1, measuring
12.1 mm in length and yielding an AMS radiocarbon date of
6265 cal. BC (Table 3.1).
earlier habitation layers (Zones B, C, D, E) resulting from a
series of intermittent short-term seasonal occupations by
small family groups that dated between about 8,000 and
10,500 years ago.
These early occupation layers at Guilá Naquitz Cave (Zones
B1, B2, B3, C, D) yielded more than 250 Cucurbita rind
fragments, a half-dozen fruit stems or peduncles, and
17 seeds that were assigned to the genus Cucurbita by Thomas
Whitaker and Hugh Cutler (Whitaker and Cutler 1971, 1986).
In their initial analysis of the Guilá Naquitz Cucurbita
assemblage, Whitaker and Cutler did not have the benefit
of being able to determine the age of seeds directly through
accelerator mass spectrometer (AMS) small sample radiocarbon
14 dating; in addition, clear standards for establishing
the domesticated status of archaeological squash specimens
had not yet been fully formulated.
The Guilá Naquitz Cucurbita seeds reanalyzed in 1996–1997
were all identified as C. pepo, based on a number of distinctive
morphological characteristics (e.g., uniform color, prominent
marginal ridge, short margin hairs, naked margin [see
Figure 3.4]; Smith 1997, 2000). Nine of these seeds fell below
SEED SIZE INCREASE OF SQUASH 27

TABLE 3.1
Direct Accelerator Mass Spectrometer Radiocarbon Dates on Early Cucurbita pepo Seeds in the Americas:
Guilá Naquitz and Phillips Spring
Seed
Length Laboratory Site and Dendrocalibrated
(mm) Sample Location Conventional Age a Age b
10.8 ß47293 Phillips Spring Unit K2 4440 ± 75 5025 ± 75
(ISM#1502)
11.4 ß91404 Guilá Naquitz C11/B1 7720 ± 60 8430 ± 60
12.0 ß91406 Guilá Naquitz C11/B1 7610 ± 60 8375 ± 60
12.1 ß91405 Guilá Naquitz C11/B1 7690 ± 50 8415 ± 50
12.5 ß100763 Guilá Naquitz C11/B2 7710 ± 50 8425 ± 50
13.2 ß100766 Guilá Naquitz E11/B1 8990 ± 60 9975 ± 60
13.8 ß100764 Guilá Naquitz E9/C 8910 ± 50 9925 ± 50
a In radiocarbon years before present.
b Intercept in calendar years before present.
the 12-mm seed-length boundary line for distinguishing
between the seeds of wild and domesticated C. pepo (compare
Figure 3.2a with Figure 3.1c–e and Figure 3.2b–g), indicating
the continuing use of wild Cucurbita gourds throughout the
early occupations of the cave. In contrast, six seeds fell at or
above the 12-mm dividing line, indicating the cultivation of
domesticated C. pepo plants by the early inhabitants of Guilá
Naquitz. The fruit stems, or peduncles, and fruit end rind
fragments having peduncle scars, recovered from the early
occupation levels at Guilá Naquitz provide further evidence
that the inhabitants of this cave both harvested wild Cucurbita
gourds and cultivated domesticated C. pepo squash. Ten
of the peduncle scars and peduncles conformed to the wild
gourd morphotype in terms of form and size (maximum
basal diameter 13 mm and roughly circular outline). A
second group of seven peduncles and peduncle scars, in
contrast, were considerably larger than the wild morphotype
profile (maximum basal diameter 14.7–23.6 mm), and
all had a distinctive angular pentagonal outline at the point
of attachment to the fruit. A characteristic 10-ridge lobing
pattern also identifies them as C. pepo (Smith 1997).
While the recovery of C. pepo seeds that are substantially
larger than those produced by wild Cucurbita gourds in the
early habitation layers of the cave provides good evidence
for the adaptive syndrome of domestication—an automatic
adaptive response by squash plants to new seed bed selective
pressures associated with deliberate and sustained planting—
the size increase in peduncles reflects deliberate human
selection for larger fruits. Such evidence of intentional
selection for desired characteristics follows more than a thousand
years after an increase in seed size indicates deliberate
planting and initial domestication.
A total of 40 radiocarbon dates have been obtained on plant
remains from Guilá Naquitz Cave (Smith 2000; Piperno
and Flannery 2001), including four direct AMS dates on
C. pepo peduncles and six direct AMS dates on C. pepo seeds
(Table 3.1). The five directly dated C. pepo seeds that fall
28 ARCHAEOLOGY AND PLANT DOMESTICATION
above the 12-mm maximum length for the wild morphotype
reference class, and which can be considered as representing
domesticated plants, are all more than 8,400 years old, with
the two oldest of the dated seeds indicating that the familysized
groups that were seasonally occupying Guilá Naquitz
were cultivating a large-seeded C. pepo squash as early as
10,000 years ago. In contrast, the first peduncles to fall above
the 13-mm upper boundary for wild morphotype Cucurbita
gourds do not appear until 8,400 years ago, and they show
a subsequent steady size increase over time (Figure 3.5).
The C. pepo Seed and Peduncle Assemblage
from the Phillips Spring Site
Located adjacent to an artesian spring on a terrace of the
Pomme de Terre River in west central Missouri (Figure 3.6),
the water-saturated habitation layers of the Phillips Spring
site yielded abundant and well-preserved plant remains when
excavated in the 1970s (Kay et al. 1980), including uncarbonized
rind fragments, seeds, and fruit stems assignable to
the genus Cucurbita. The earliest habitation zone at Phillips
Spring, Unit K2, sealed beneath a large rock-lined hearth,
yielded three standard radiocarbon dates (4310 ± 70, 4222 ±
57, 4240 ± 80 BP radiocarbon years), along with approximately
125 whole seeds and fragments identified as C. pepo
(Kay et al. 1980: 814; King 1980: 218, 1985: 81). When
initially analyzed, 62 of the C. pepo seeds from Unit K2 (the
“squash and gourd zone”) provided both length and width
measurements. They ranged in length from 8.3 to 12.2 mm,
with a mean length of 10.5 mm (King 1985: 82). Fifteen
years later, reanalysis of the Phillips Spring K2 Cucurbita
assemblage produced the same results, even though length
and width measurements could be obtained on only 45 seeds
(Figure 3.1a; Smith 2000: 54). Assignment of the Unit K2
Cucurbita seeds to C. pepo was also confirmed (based on
marginal ridge and hair morphology), as was the temporal
placement of the “squash and gourd zone.” A direct AMS

FIGURE 3.5 Increase in the size of peduncles of
domesticated Cucurbita pepo in preceramic habitation zones
of Guilá Naquitz Cave between ca. 6500 and 5800 BC
(see Smith 2000: 40).
radiocarbon date of 4440 ± 75 BP radiocarbon years (5025
calibrated calendar years BP) was obtained on one of the Unit
K2 seeds (Table 3.1; Smith 2000: 58).
Generally accepted as representing an early stage of domesticated
C. pepo in the eastern United States, the Unit K2
Phillips Spring seed assemblage has a mean length value
larger than all but one of the 13 wild Cucurbita gourd
reference taxa listed in Figures 3.1 and 3.2. Significantly,
although only two Phillips Spring seeds met or exceeded
the 12.0-mm domestication boundary employed for the
Guilá Naquitz assemblage, 12 of the 45 Unit K2 C. pepo
seeds measured for the present study exceeded the 11.0-mm
wild seed length ceiling proposed for the eastern United
States, providing strong evidence for deliberate planting,
an adaptive response to seedbed selective pressure, and
the independent domestication of C. pepo ssp. ovifera in the
eastern United States.
The four fruit-end fragment peduncle scars in the Unit K2
Cucurbita assemblage, in contrast, show no indication of
morphological changes beyond the parameters of the wild
morphotype gourd profile. They compare closely to the
wild Ozark gourd (C. pepo ssp. ovifera var. ozarkana) in both
diameter and circular outline, and they appear to be from
small globular fruits. As is the case in the developmental
sequence for the Mexican lineage of domesticated C. pepo,
a wide range of changes in fruit morphology indicative
of deliberate and sustained human selection also appears
in the 2,000-year span following the 5000 BP Unit K2
Phillips Spring assemblage and its evidence for initial domestication
of C. pepo in the eastern United States. These changes
Osage
Missouri
River
Warsaw
Pomme
FIGURE 3.6 The location of the Phillips Spring archaeological
site in south central Missouri.
include a diversification of fruit forms, surface lobing
and warting, and an increase in both fruit size and rind
thickness (Cowan 1997: 73).
Discussion—Future Research Directions
Fristoe
Boney Spring
Rodgers Shelter
Wheatland
N 0 5 km
Phillips Spring
This chapter marshals archaeological evidence in support
of the proposition that pepo squash (Cucurbita pepo) was
independently domesticated twice in the Americas: the
pumpkin lineage (Cucurbita pepo ssp. pepo in Mexico by
10,000 years ago, and the acorn–summer squash lineage
(Cucurbita pepo ssp. ovifera) in the eastern United States by
5,000 years ago. For each of these separate domestication
processes, the supporting arguments rest on an observed
morphological change—an increase in the size of pepo squash
seeds recovered from an archaeological context beyond what
has been documented in modern reference class taxa of
wild Cucurbita gourds. It is important to keep in mind that,
while the evidence compiled to date and presented here
constitutes a good beginning—an initial general spatial and
temporal outline of domestication in this species—there is
SEED SIZE INCREASE OF SQUASH 29
Terre
River
Blackwell Cave
Hermitage

still considerable room for strengthening the supporting
arguments, and for expanding the context and scope of
consideration of C. pepo domestication.
The most obvious way in which these supporting
arguments can be strengthened is through enlarging the
modern reference class of seed size measurements, thereby
ensuring that the full range of taxonomic and geographical
variation in seed size for all of the present-day wild taxa
of Cucurbita gourds is encompassed. This is particularly
true for the three modern wild taxa that have the greatest
genetic similarity to the eastern acorn–summer squash
lineage. While two of the three taxa that compose the C. pepo
ssp. ovifera wild progenitor gourd complex—the Ozark and
Texas wild gourds (C. pepo ssp. ovifera varieties texana and
ozarkana)—have been studied to some extent throughout
their geographical range, and have yielded reasonably large
and representative samples of seeds for modern comparison
collections, the third (C. pepo ssp. ovifera var. fraterna)
is still relatively poorly documented in terms of both seed
size and natural habitat. Based on the apparent strong
selective pressures controlling seed and fruit size in all of
the present-day taxa of wild morphotype Cucurbita gourds,
however, any expansion of modern reference class seed size
values beyond that already documented would not be
expected.
Of even more importance, in terms of strengthening
our modern reference class of wild Cucurbita taxa, will be
to identify in Mexico, if they are still extant, modern descendant
populations of the wild progenitor of the Mexican
pumpkin lineage of domesticated pepo squash. If such
modern populations of the wild gourd that gave rise to
Cucurbita pepo ssp. pepo more than 10,000 years ago still
survive somewhere in Mexico, they have not yet been located
and documented, in spite of fairly substantial field survey
coverage for wild Cucurbita taxa.
At the same time, it will be just as important to expand the
reference class of ancient collections of wild Cucurbita taxa
recovered from human contexts and from natural deposits
(e.g., Page-Ladson, Figure 3.1b) over broad spatial and
temporal ranges. It is important to be able to document
that the same strong selective pressures operating to control
seed size in modern wild Cucurbita gourds were also present
in the past, and that wild gourds in the early Holocene
did not produce seeds that were larger than their present-day
descendant populations. This ancient reference class of
Cucurbita represents an important aspect of any supporting
argument for domestication. A claim of domesticated
status for squash seeds recovered from an archaeological
context based on seed size increase is considerably strengthened
if the candidate for early domesticate seeds can be
shown not only to be larger than those produced by modern
wild taxa, but also to be larger than seeds produced by
presumably wild gourd taxa of the past. The ideal supporting
argument in this regard would be a rich and well-documented
deep-time-depth regional archaeobotanical record of
30 ARCHAEOLOGY AND PLANT DOMESTICATION
human use of a small-seeded wild Cucurbita gourd, leading
up to the appearance of a larger seeded (domesticated) form
inthe archaeological sequence. Supporting evidence of this
kind does exist to some extent in both Mexico (Figure 3.2)
and eastern North America (Figure 3.1) in the form of small
squash seeds, likely from wild taxa, occasionally being
recovered from scattered archaeological contexts that predate
the appearance of large seeds from early domesticates. This
reference class, however, needs to be substantially improved
in terms of both overall seed count and temporal and
spatial coverage.
Another obvious area of future research regarding the early
history of domesticated pepo squash in the Americas will
involve tracing the timing of introduction of the Mexican
pumpkin lineage of pepo squash into eastern North America
from the Southwest, and the subsequent manner in which
it was variously added into the existing indigenous food
production economies of different regions of the East. There
has been considerable recent research on the initial introduction
of other crop plants from Mexico, including other species
of squash (e.g., Fritz 1994), and it should be possible to
distinguish in the archaeological record between the indigenous
acorn–summer squash lineage (C. pepo ssp. ovifera) and
the introduced Mexican pumpkin lineage (C. pepo ssp. pepo)
on the basis of genetic profiles as well as seed, fruit, and
peduncle morphology.
Finally, at the same time that there is considerable room for
strengthening and expanding the supporting arguments
for when and where domestication of this important crop
plant took place, there is also a great deal to be learned regarding
the role of this species in the low-level food production
economies of the human societies that first domesticated it
in Mexico and the eastern United States so long ago, and
the extent to which it represented a significant change, or if
it initially at least was just a modest supplement to an
otherwise stable and relatively secure way of life.
References
Cowan, C. W. 1997. Evolutionary changes associated with the
domestication of Cucurbita pepo: Evidence from eastern
Kentucky. In People, plants, and landscapes, K. Gremillion (ed.),
pp. 63–85. Tuscaloosa: University of Alabama Press.
Decker-Walters, D., T. Walters, C. W. Cowan, and B. D. Smith.
1993. Isozyme characterization of wild populations of Cucurbita
pepo. Journal of Ethnobiology 13: 55–72.
de Wet, J. M. J. and J. R. Harlan. 1975. Weeds and domesticates:
Evolution in the man-made habitat. Economic Botany 29:
99–107.
Flannery, K. 1986. Guilá Naquitz. Archaic foraging and early
agriculture in Oaxaca, Mexico. New York: Academic Press.
Fritz, G. 1994. Precolumbian Cucurbita argyrosperma ssp.
argyrosperma in the western woodlands of eastern North
America. Economic Botany 48: 280–292.
Harlan, J. and J. M. J. deWet. 1965. Some thoughts on weeds.
Economic Botany 18: 16–22.

Harlan, J. J., M. J. deWet, and E. G. Price. 1973. Comparative
evolution of cereals. Evolution 27: 311–325.
Kay, M., F. B. King, and C. K. Robinson. 1980. Cucurbits from
Phillips Spring: New evidence and interpretation. American
Antiquity 45: 806–822.
King, F. B. 1980. Plant remains from Phillips Spring, a multicomponent
site in the western Ozark highland of Missouri. Plains
Anthropologist 25: 217–227.
———. 1985. Early cultivated Cucurbits in eastern North America.
In Prehistoric Food Production in North America, R. I. Ford (ed.),
pp. 73–98. Ann Arbor, Mich.: Museum of Anthropology,
University of Michigan, Anthropological Papers No. 75.
Lentz, D. W., M. E. D. Pohl, K. O. Pope, and A. R. Wyatt. 2001.
Prehistoric sunflower (Helianthus annuus L.) domestication in
Mexico. Economic Botany 55: 370–376.
Nee, M. 1990. The domestication of Cucurbita (Cucurbitaceae).
Economic Botany 44 (supplement): 56–69.
Newsom, L., S. D. Webb, and J. S. Dunbar. 1993. History and
geographic distribution of Cucurbita pepo gourds in Florida.
Journal of Ethnobiology 13: 75–79.
Piperno, D. and K. Flannery. 2001. The earliest archaeological
maize (Zea mays L.) from highland Mexico: New accelerator
mass spectrometry dates and their implications. Proceedings of
the National Academy of Sciences 98: 1324–1326.
Piperno, D. and K. Stothert. 2003. Phytolith evidence for Early
Holocene Cucurbita domestication in southwest Ecuador.
Science 299: 1054–1057.
Robinson, R. W. and D. Decker-Walters. 1997. Cucurbits. New York:
CAB International.
Sanjur, O., D. Piperno, T. Andres, and L. Wessel-Beaver. 2002.
Phylogenetic relationships among domesticated and wild
species of Cucurbita inferred from a mitochondrial gene:
Implications for crop plant evolution and areas of origin.
Proceedings of the National Academy of Sciences, USA 99: 535–540.
———. 2004. Using molecular markers to study plant domestication:
The case of Cucurbita. In Biomolecular archaeology:
Genetic approaches to the past. D. M. Reed (ed.), pp. 128–
150. Occasional Paper No. 32 of the Center for Archaeological
Investigations, Southern Illinois University, Carbondale.
Carbondale, Ill.: CAI, Southern Illinois University, Carbondale.
Smith, B. D. 1997. The initial domestication of Cucurbita
pepo in the Americas 10,000 years ago. Science 276: 932–934.
———. 1998. The emergence of agriculture. New York: W.H.
Freeman.
———. 2000. Guilá Naquitz revisited. In Cultural evolution:
Contemporary viewpoints, G. Feinman and L. Manzanilla (eds.),
pp. 15–59. New York: Kluwer Academic/Plenum Publishers.
———. 2002. Rivers of change (paperback edition). Washington,
D.C.: Smithsonian Institution Press.
Whitaker, T. and H. Cutler. 1971. Prehistoric cucurbits from the
Valley of Oaxaca. Economic Botany 25: 123–127.
———. 1986. Cucurbits from preceramic levels at Guilá Naquitz.
In Guilá Naquitz: Archaic foraging and early agriculture in Oaxaca,
Mexico, K. Flannery (ed.), pp. 275–279. New York: Academic Press.
Zohary, D. 1996. The founder crops of southwest Asian agriculture.
In The origins and spread of agriculture and pastoralism in
Eurasia, D. Harris (ed.), pp. 142–158. Washington, D.C.:
Smithsonian Institution Press.
SEED SIZE INCREASE OF SQUASH 31