The Solutrean Atlantic Hypothesis: A View from the Ocean
Kieran Westley1,2,* and Justin Dix3
Abstract - One current hypothesis for the Pleistocene peopling of the Americas invokes a dispersal by European huntergatherers
along a biologically productive “corridor” situated on the edge of the sea-ice that fi lled the Atlantic Ocean during
the Last Glacial Maximum (LGM). In this paper, we assert that critical paleoceanographic data underpinning this hypothesis
has not yet been examined in suffi cient detail. To this end, we present data which show that the corridor may not have
existed, and that, if it did, its suitability as a migration route is highly questionable. In addition to demonstrating that the
hypothesized migration was unlikely, this highlights the importance of integrating paleoceanographic and archaeological
data in studies of paleo-coastal societies.
1Department of Geography, Memorial University, St. John’s, Newfoundland A1B 3X9, Canada. 2Archaeology Unit, Department
of Anthropology and Archaeology, Memorial University, St. John’s, Newfoundland A1C 5S7, Canada. 3School of
Ocean and Earth Sciences, University of Southampton, National Oceanography Centre, European Way, Southampton SO14
3ZH, UK. *Corresponding author - kwestley@mun.ca.
Introduction
The timing of the initial colonization of the
Americas is one of the great unsolved questions
of prehistoric archaeology. For much of the last
half-century, the orthodox view was dominated by
proponents of the “Clovis-fi rst” argument. According
to this theory, the fi rst colonists were Siberian
hunter-gatherers who travelled to Alaska across the
Bering Sea continental shelf, which at the time was
exposed by lowered sea-levels. From here, they
dispersed south through an ice-free corridor dividing
the Laurentide and Cordilleran ice sheets which
covered most of landscape above ≈50°N, before
spreading rapidly across North America (Fig. 1).
Their presence was manifest by a distinctive toolkit
of fl uted lithic points (the eponymous Clovis point)
found across the continent and originally radiocarbon-
dated to between 11.5–10.9 (14C) ka BP (Fiedel
1999) and recently refi ned to 11.05–10.8 (14C) ka BP
(Waters and Stafford 2007). In calendar years, this
equates to a maximum age span of 13.11–12.66 or
13.25–12.8 cal ka BP, depending on whether a dendrochronological
or coral-based calibration is used
(Waters and Stafford 2007).
However, this argument was undermined by the
presence of archaeological sites scattered across
the Americas that predated Clovis. Although many
were demonstrated to be the product of contaminated
radiocarbon dates, stratigraphic mixing, or
naturally rather than anthropogenically produced
artifacts, there remained several sites that resisted
critique (Fiedel 2000). Notable examples include
the Monte Verde (Chile, dated to 12.5–12 [14C] ka
BP), Meadowcroft (Pennyslvania, USA, 19–13 [14C]
ka BP), and Cactus Hill (Virginia, USA, dated to
16.9–15 [14C] ka BP) sites (Dillehay 1997, Feathers
et al. 2006, Fiedel 1992). More recently, Waters and
Stafford’s (2007) redating of Clovis suggests that the
temporal gap between Clovis and the youngest welldated
sites in South America was a minimum of 200
to a maximum of 350 calendar years, a timeframe
within which it is improbable that humans could
enter North America, adapt to a wide range of environments
and undertake a single migration of 14,000
km to populate South America. In short, the current
evidence provides a strong indication that the Clovis
people were not the fi rst occupants of the Americas.
The presence of a pre-Clovis population in turn
requires consideration of their migration route into
the Americas. In this instance, the ice-free corridor
hypothesis proves to be problematic. Firstly, it
contains relatively little archaeological evidence.
Moreover, what evidence there is postdates, or coincides
with Clovis (Waguespack 2007). Secondly,
it is still an open question whether it was capable
of supporting past humans (Waguespack 2007).
For example, Arnold (2002) has suggested that the
corridor’s lack of datable organic material predating
11 (14C) ka BP implies it was devoid of habitable
environments. Thirdly, better dating has constrained
its opening between 13–12.5 (14C) ka BP (Dyke et
al. 2003), implying it was not a pathway available
for a pre-Clovis dispersal given the age of the dated
sites. In short, an alternative route into the Americas
is required.
The most widely discussed alternative is a
coastal route from Beringia down the Pacific Northwest
coast of North America (Fig. 1). This theory
was first proposed by Knut Fladmark (1979) over
twenty years ago, but was not seriously considered
until the last decade due to the supposition that the
relevant evidence had been eroded or submerged
by rising sea-levels. According to this hypothesis,
migrants circumvented the Cordilleran ice sheet by
using boats to hop between unglaciated sections of
the coastline. Recent work has supported it by identifying
such unglaciated refugia on the continental
shelf off British Columbia and southern Alaska
2008 Journal of the North Atlantic 1:85–98
86 Journal of the North Atlantic Volume 1
(Heaton et al. 1996, Hetherington et al. 2003, Mandryk
et al. 2001).
Another alternative, proposed by Bruce Bradley
and Dennis Stanford (2004) comes from the other
direction. They propose a migration across the Atlantic
by European hunter-gatherers, using boats to
follow the extensive pack ice that fi lled the North
Atlantic at the height of the last ice age, the Last
Glacial Maximum (LGM) (Fig. 1). Along the way,
they were sustained by the rich marine resources,
particularly marine mammals such as harp seals
that are argued to have congregated along the edge
of the ice, hence the description of the route as an
“ice-edge corridor.” Their view is based primarily on
lithic technology, more specifi cally the suggestion
that Siberian sites do not have a lithic technology
that resembles a Clovis precursor, and that greater
technological similarities can be found between
lithic assemblages from France and Spain (the Solutrean
technocomplex; dated to ≈25–18 cal ka BP)
and Clovis. They also believe artifacts from three
pre-Clovis sites in eastern North America (Meadowcroft,
Cactus Hill, and Page-Larson) are transitional
between the Solutrean and Clovis, thus fi lling the
time gap between them, while also pointing out that
the earliest Clovis dates come from the southeast of
North America, rather than the northwest, as might
be expected given an Asian origin.
This view has been heavily critiqued on a number
of fronts including: a lack of evidence for a signifi -
cant marine adaptation in the Solutrean; similarities
between European and North American tool types
being more apparent than real; and the 5000-year
time gap between the Solutrean and Clovis (Straus
2000, Straus et al. 2005). Similarly, any rebuttals
have been based primarily around issues of lithic
technology (Bradley and Stanford 2006).
One aspect that has not been examined in as much
detail, by both proponents and opponents of the hypothesis,
is the “ice-edge” corridor itself, a factor
that one would presume to be critical to the success
or failure of the hypothesized dispersal. Bradley
and Stanford’s descriptions of Solutrean marine
or ice-based settlement and resource procurement
systems are, as they freely admit (2004:470), informed
speculation. Meanwhile, Straus et al. (2005:
517) recognized the need to test these descriptions
with paleo-environmental data, but stopped short
of doing so on the basis that “This is not a matter
to be left to archaeologists.” However, ignoring the
paleo-environmental record provides a somewhat
imbalanced view of the past. Even without resorting
to environmental determinism, it should be clear that
the human activities operate within broad practical
boundaries set by the environment. Indeed, the need
for an understanding of paleo-environment is well
established in prehistoric archaeology in relation
to terrestrial sites (e.g., Bell and Walker 2005, Van
Andel and Davies 2003). It therefore begs the question
why the same should not be true of the marine
environment, especially considering how critical it
is to the proposed dispersal. Consequently, the aim
of this paper is to test the Solutrean hypothesis by
primarily using relevant paleo-environmental and
paleoceanographic data.
This inquiry can be framed by two broad questions:
1. Did an ice-edge corridor actually exist at
the period in question?
2. If so, was it actually amenable to migration
and dispersal?
The remainder of this paper will address these two
questions by both reviewing North Atlantic paleoceanography
and the implications of this for the
Figure 1. Competing hypotheses for routes taken by hunter-gatherers during the initial colonization of the Americas. Ice
sheet limits and sea-levels are those of the Last Glacial Maximum (c.18–24 cal ka BP). Note that the ice-free corridor was
only opened after the LGM (c. 16 cal ka BP). European and North American ice limits from Carr et al. (2006) and Dyke et
al. (2003) respectively. The paleo-shoreline has been placed at -120 m and represents the LGM glacio-eustatic sea-level fall
(Peltier and Fairbanks 2006). This depiction is therefore a fi rst-order approximation, with areas in close proximity to the ice
sheets experiencing different patterns of sea-level change (see Lambeck and Chappell 2001 for more information).
2008 K. Westley and J. Dix 87
proposed dispersal. A specifi c focus will be placed
on the conditions in the Bay of Biscay, as this borders
the Solutrean heartland of southern France and
the Iberian Peninsula and was therefore the most
likely location for the development of a Solutrean
maritime adaptation, if one occurred.
The North Atlantic at the LGM
The proposed Solutrean migration took place
during the height of the last glacial period; an
interval commonly referred to as the Last Glacial
Maximum (LGM) and dated to between 18 and 24 cal
ka BP as defi ned by the EPILOG project (Mix et al.
2001). During this time, high and mid-latitude conditions
were much colder and drier than at present,
characterized by the expansion of ice sheets, polar
desert, and steppe tundra on land, and low sea surface
temperatures (SSTs) and greater sea-ice extents at sea
(Kutzbach et al. 1998, Ray and Adams 2001).
For many years, reconstructions of North Atlantic
paleoceanography during this interval were
based on the pioneering CLIMAP (Climate Long
Range Investigation, Mapping, and Prediction) project
(CLIMAP Project Members 1976, 1981). This
work, undertaken in the 1970s, provided quantitative
reconstructions of LGM terrestrial and marine
climate, based on proxy records. According to this,
LGM SSTs in the North Atlantic dropped dramatically
relative to the present day. For example, at
50°N, they fell 12 °C below present (CLIMAP
Project Members 1976). The temperature drop was
particularly dramatic on the Northwest European
margin as the warm North Atlantic Drift (NAD) current,
which presently keeps seasonal temperatures
above the latitudinal average, was defl ected south.
Consequently, the southern boundary of the polar
front (the transition zone between cold subpolar and
warm subtropical waters) was located at ≈37–43°N,
approximately the same latitude as the Portuguese
and North Spanish coasts (Ruddiman and McIntyre
1981). As a consequence of these lowered temperatures,
the distribution of sea-ice was more extensive
and believed to cover much of the North Atlantic,
reaching as far south as the French Atlantic coast
during the winter (CLIMAP Project Members 1981).
It is this ice that Bradley and Stanford (2004) regard
as the critical link in their hypothesis of trans-Atlantic
migration.
In recent years, new data and more advanced
scientifi c techniques have superseded some of the
conclusions of CLIMAP. With respect to North
Atlantic paleoceanography, important examples are
the GLAMAP (Glacial Atlantic Ocean Mapping:
Pfl aumann et al. 2003) and MARGO (Multi-proxy
Approach for the Reconstruction of the Glacial
Ocean surface; Kucera et al. 2005) projects, both
of which re-assessed LGM SSTs and sea-ice cover
using new and more refi ned techniques of proxy
reconstruction, as well as better constraints on the
timing of paleoceanographic changes. One key
aspect of the MARGO project was its use of multiple
proxies to measure paleoceanographic change.
These ranged from measurements of chemical
changes in the bodies of marine micro-organisms
(a refl ection of climate-induced chemical changes in
ocean water) to biological transfer functions which
measure change on the basis that particular communities
of micro-organism species can only live
within particular environmental ranges. Although
the different proxies provided varying quantitative
estimates of paleo-SSTs (see review in De Vernal et
al. 2006), they are consistent in two areas. Firstly,
they show that the LGM North Atlantic was warmer,
and secondly that LGM sea-ice was less extensive
and much more seasonal than previously estimated
by CLIMAP.
The results of the MARGO Project based on
biological transfer functions for two proxies—dinocysts
and planktonic foraminifera—are displayed
in Figure 2. While there are quantitative differences
between the two (for example, compare Figs. 2a and
2c), the overall pattern they reconstruct is consistent.
More specifi cally, winter sea-ice extended down to
≈45–50°N at maximum. During summer, the NW
European margin was seasonally ice free almost to
80°N, with rare excursions down to ≈60–65°N and
quasi-permanent ice restricted to the northeast Canadian
and east Greenland coasts (Figs. 2e and f). The
dinocyst reconstructions also provide a quantitative
estimate of ice duration, namely that winter ice only
persisted for 1–3 months each year across most of
the North Atlantic (Fig. 2f). Further important features
to note are a broad ice-free channel inferred
for the central Atlantic and that the Bay of Biscay,
on average, experienced winter sea-ice for less than
one month per year (De Vernal et al. 2005, De Vernal
et al. 2006, Sarnthein et al. 2003). In short, the
remarkable seasonality of the LGM North Atlantic
contrasts with the oft-assumed concept of a perennially
ice covered ocean.
The improved time resolution of recent deep-sea
records has also allowed greater insight into the pattern
of paleoceanographic change over time. In this
instance, the majority of the evidence shows that the
coldest conditions in the North Atlantic did not occur
during the LGM as previously believed, but during
two rapid events on either side of it; Heinrich Events
1 and 2, dated to ≈17 and 24 cal ka BP respectively
(Hemming 2004). During these brief (500 ± 250
years) intervals, SSTs fell drastically and the North
Atlantic was fi lled by ice. However, this did not take
the form of a continuous sheet of sea-ice, but was
comprised of massive discharges of icebergs from
88 Journal of the North Atlantic Volume 1
the North American and European ice sheets reaching
as far south as 40°N. The most detailed evidence
of these events comes from off the Portuguese coast
where favourable conditions permit the formation of
long high-resolution deep-sea records. For example,
cores from this area have LGM SSTs of 13–17°C
compared to lows of 5–10°C for Heinrich Events
and also contain layers of ice-rafted debris (IRD)
deposited by the fl eet of melting icebergs (De Abreu
et al. 2003, Pailler and Bard 2002).
Similar patterns prevailed in the Bay of Biscay.
Here, a high-resolution record (core MD 95-2002;
Figure 2. Quantitative reconstructions of LGM North Atlantic paleoceanography based on two different proxies: dinocysts
and planktonic foraminifera. Data from De Vernal et al. (2004) and Weinelt (2004) (See also De Vernal et al. 2006, Kucera
et al. 2005). a) Summer SSTs from planktonic foraminifera. b) Winter SSTs from planktonic foraminifera. c) Summer SSTs
from dinocysts. d) Winter SSTs from dinocysts. e) Sea-ice extents from planktonic foraminifera: triangles show core sites
with evidence of summer and winter ice. Heavy black line represents the extent of perennial ice, and dashed line is the
maximum extent of winter ice (based on Sarnthein et al. 2003). f) Sea-ice extents from dinocysts: triangles show core sites
with evidence of the duration of ice in months per year. Heavy black line represents the extent of perennial ice, and dashed
line is the maximum extent of winter ice (based on De Vernal et al. 2006).
2008 K. Westley and J. Dix 89
see Fig. 2c for core location) covers the LGM
and post-LGM period and clearly demonstrates
millennial-scale changes in ocean conditions
(Fig. 3). This pattern is revealed firstly by the
presence of IRD, which reaches maximum values
during Heinrich Events 1 and 2, but drops dramatically
during the intervening period—the LGM. A
second proxy is the presence of the planktonic
foraminifera Neogloboquadrina pachyderma(s),
a subpolar species which presently inhabits North
Atlantic waters above 65°N. High concentrations of
N.pachyderma(s) are therefore a clear sign of cold
conditions and in this instance coincide with Heinrich
Events 1 and 2 and the GS-1 stadial identified
in the Greenland ice cores. Importantly, the interval
between Heinrich Events 1 and 2 was characterized
by lower quantities of N.pachyderma(s), and can
be divided into an initial cold period followed by
a period of fluctuating, often warmer, temperatures
brought about by the increased advection of warm
North Atlantic Drift water into the Bay. A third
proxy is the dinocyst Algidasphaeridium minutum,
a species that tends to be associated with sea-ice. It
is noteworthy that its highest concentrations occur
before and after the LGM, substantiating the results
described earlier and in Figure 2 (Eynaud 1999,
Zaragosi et al. 2001).
Another important record from the Bay of Biscay
is core SU8147 (see Fig. 2c for core location).
Though it lacks a published radiocarbon timescale
and is of lower resolution, it can be correlated to the
MD95-2002 timescale by virtue of similar changes
in faunal composition (Westley 2006). Importantly,
this core provides quantifi cation of the paleoceanographic
changes described above. Noteworthy features
are that LGM conditions were subarctic, though
not low enough to form perennial sea-ice: February
temperatures are believed to have ranged between
1–4 °C (±2 °C), with sea-ice cover of between 1–2
months per year at most. Conversely, during Heinrich
1, winter SSTs reached as low as 0–1 °C while
sea-ice cover potentially reached up to 6 months per
year. In summary, a variety of evidence from the
North Atlantic indicates that LGM conditions were
not as cold and icy as previously believed. Instead
these circumstances were prevalent during the short
stadial events on either side of it.
Implications for the Trans-Atlantic Crossing:
Existence of the Ice-Edge Corridor
Before assessing the implications of the previous
section for the hypothesized migration, it is necessary
to constrain the chronology of the Solutrean
accurately so as to compare it with the paleoceanographic
evidence. This analysis will be done by
calibrating radiocarbon dates from Solutrean sites
and plotting them alongside paleoceanographic
evidence calibrated on the same timescale (Fig. 4).
This comparison clearly shows that Solutrean sites
correlate for the most part with Heinrich Event 2 and
the LGM. The fi rst question to consider is whether
suffi cient ice actually existed across the Atlantic to
form a migration corridor during the time period
encompassed by the Solutrean.
The revised views of North Atlantic paleoceanography
do indeed show that sea-ice was more
extensive at the LGM relative to the present. However,
they also show that the actual duration of ice
cover was much less and the differences between
summer and winter ice extents were much greater
than previously believed. The actual duration for
which the coasts of eastern North America and NW
Europe were connected was probably very small—
of the order of 1–3 months per year (Fig. 2). Potential
migrants therefore had a very restricted time
window within which to cross the ocean. Moreover,
in the Bay of Biscay, extensive winter ice probably
only have existed for less than a month, and possibly
up to a maximum of two months per year. Focusing
specifi cally on harp seals, regarded by Bradley and
Stanford (2004) as a particularly important resource
(“A Solutrean hunter must have been awe-struck
when he watched for the fi rst time a pristine seal
colony stretching for as far as he could see, basking
on an ice fl oe as it drifted towards the shore.”
[2004:470]), the most southerly modern extremes
of harp seal congregations on ice are located in the
waters of the Gulf of St. Lawrence and off northeast
Newfoundland (Renouf and Bell 2006). These areas
presently have ice cover 2–4 months per year (De
Vernal and Hillaire-Marcel 2000). These facts lead
one to question whether an intensively ice-based
marine mammal hunting subsistence strategy could
actually have developed in the Bay of Biscay, given
its lower ice concentrations.
Admittedly, the Solutrean does overlap to a
small degree with Heinrich Event 1 (more specifically,
the Heinrich 1 precursor rather than the
maxima of the ice-rafting event) and completely
with Heinrich Event 2, during which ice extents
increased considerably. Nonetheless, even if it were
argued that the hypothesized dispersal took place
during these events, there is still the obstacle that
the Atlantic sea-ice was composed of discontinuous
icebergs rather than a largely continuous and flat
mass of ice, a platform less suited to the aggregation
of dense concentrations of marine mammals.
In addition, these were drifting south and east with
the dominant wind and ocean currents, as shown
by the presence of North European and Canadian
IRD in the Bay of Biscay (Zaragosi et al. 2001),
directly opposite to the proposed migration. Furthermore,
if dispersal occurred at Heinrich 2, this
90 Journal of the North Atlantic Volume 1
would increase the time gap between Clovis and the
Solutrean to more than 10,000 years, weakening the
idea that the two were connected.
The greater seasonality of the LGM North
Atlantic also requires us to consider the ice-edge
corridor as a dynamic entity, rapidly altering its geography
every year. Bradley and Stanford’s (2004)
view assumes a synchronous northward retreat of
the ice edge so as to maintain a viable “bridge”
or “corridor.” They suggest that Solutrean hunters
progressively moved further from the Bay of
Biscay during phases of climate warming as the
ice retreated north in pursuit of ice-edge dwelling
seals until they inadvertently reached the other
2008 K. Westley and J. Dix 91
side of the bridge. An obstacle to this route would
have been the ice-free channel in the central North
Atlantic identified by Sarnthein et al. (2003) and
shown in Figure 2e. If this channel expanded during
the initial phases of the seasonal ice melt, it would
effectively split the ice-edge corridor. While the exact
pattern of seasonal ice melt is still uncertain, the
presence of short-duration (i.e., 0–1 month/yr) ice
in the vicinity of the channel (Fig. 2f) could be taken
as substantiating evidence. This scenario would
then necessitate an open-water crossing to reach the
other side, and if the Solutrean hunters were in fact
tracking the ice edge, then northward movement up
the European margin would be more likely.
The speed of seasonal ice melt is also critical
if one takes into account the time required to traverse
the LGM North Atlantic. Since there is little
information in the Solutrean Atlantic Hypothesis
on the types of boat used, the speed of the proposed
migration, or the proportions of time spent on the
water versus the ice, we must turn to computer
simulations of LGM boat journeys developed by
Figure 3 (opposite page). Late Pleistocene paleoceanographic conditions in the Bay of Biscay based on cores MD95-2002
and SU8147. MD95-2002 has a well-constrained radiocarbon-based chronology (Eynaud et al. 2007, Zaragosi et al. 2001),
which in this instance has been calibrated using the CalPal Hulu 2007 curve and the CalPal program (Weninger and Jöris
2008, Weninger et al. 2007). SU8147 lacks a published radiocarbon timescale, but can be correlated with MD95-2002 on the
basis of synchronous changes in microfossil communities. The pattern of paleoceanographic change allows the period to be
divided into specifi c climatic intervals. In this case, the LGM—between 24–18 cal ka BP—can be divided into two phases:
an initial cold phase (IC) and a subsequent warmer and fl uctuating phase during which pulses of warm North Atlantic Drift
water entered the Bay (NAD Pulses). H2 and H1 refer to Heinrich Events 1 and 2, respectively, when temperatures fell
and iceberg incursion was common. H1p refers to the Heinrich 1 precursor—the interval during which iceberg rafting was
initiated. GI-1 and GS-1 are respectively interstadial and stadial periods that are also visible in the Greenland ice cores.
Grey bars highlight the coldest intervals. SU8147 SST and sea-ice reconstructions show the maximum, minimum, and most
probable values as determined by the original investigators (Turon et al. 1995). MD95-2002 provides qualitative indications
of change: IRD concentrations rise when icebergs are present, and A. minutum and N. pachyderma(s) inhabit sea-ice and
subpolar environments, respectively (data courtesy of F.Eynaud).
Figure 4. Relative probability distribution of radiocarbon dates from Solutrean sites plotted against the MD95-2002 paleoceanographic
record. Both datasets calibrated using the CalPal Hulu 2007 curve and the CalPal program (Weninger and
Jöris 2008, Weninger et al. 2007). Solutrean dates were obtained from the S2AGES database of radiocarbon dates (Gamble
et al. 2005) provided courtesy of W. Davies and C. Gamble. This database contains a means of auditing dates in order to
exclude poor or inaccurate dates. In this Figure, an unaudited sample has been used so as to obtain the widest possible
chronological limits. Hence, the outlying dates such as in the Holocene and GS-1 are “bad” dates, resulting from issues such
as sample contamination (Pettitt et al. 2003). The unaudited data provide a Solutrean duration between 26 and 18 cal ka BP,
whilst the use of audited dates refi nes the time period to between 25 and 18 cal ka BP (based on 17 dates from 5 sites).
92 Journal of the North Atlantic Volume 1
evenly throughout the year rather than having intense
seasonal blooms. A more important factor may
have been the increased spring and summer insolation
brought about by the orbital patterns of the time
(Loutre et al. 2004), which would have enhanced
productivity, but only during seasons when the ice
was melting or absent.
Secondly, the issue of LGM productivity is a
complex one with some studies suggesting greater
or equal productivity compared to the Holocene, and
others indicating that it was lower (Villanueva et al.
2001). The differences arise because of sample location—
i.e., productivity is not uniformly distributed
across the world—and the fact that different proxies
provide varying estimates. Therefore, while overall
LGM productivity levels seem to have been higher
than present as evidenced by reduced carbon dioxide
levels (which are at least partially the result of
greater uptake of CO2 due to increased phytoplankton
productivity; Abrantes 2000), there are questions
over where these productivity spikes were located.
Consequently, Bradley and Stanford (2004) are
correct in identifying that the strong atmospheric
circulation of the LGM resulted in enhanced upwelling
and marine productivity in the Atlantic (Abrantes
2000, Pailler and Bard 2002). What they fail to mention
is that intense coastal upwelling systems are
restricted to certain areas, specifi cally those in which
shore-parallel winds move ocean water such that cold,
nutrient-rich deep water is upwelled from beneath the
main current body (Pickard and Emery 1990). On the
European margin, the Portuguese coast rather than
the Bay of Biscay experiences such systems, and in
fact represents the northernmost limit of the North
Atlantic upwelling system both now and during the
LGM (Vautravers and Shackleton 2006). Unlike the
Portuguese margin where northerly winds generate
the upwelling, the Bay of Biscay was dominated by
westerly winds at the LGM (Kageyama et al. 2006),
even further reducing the possibility of a strong upwelling
system developing here.
Looking at the other mechanisms, it is true that
loess mobilization was more prevalent during cold,
dry glacial periods (Lowe and Walker 1997), and
may have played a role in enhancing productivity.
However, the role of icebergs is more questionable.
Although IRD deposition does increase mineral input
into the oceans, a number of studies have correlated
episodes of iceberg rafting or increased
sea-ice extent during the Pleistocene with decreased
productivity (e.g., Auffret et al. 1996, Pailler and
Bard 2002). Firstly, the ice reduces the amount of
light available for phytoplankton photosynthesis, in
turn reducing primary productivity at the base of the
food chain. Secondly, melting icebergs create a cold,
low salinity “lid” on the surface of the ocean. This
enhanced stratifi cation inhibits the mixing of nutrients
between different water layers, further reducing
Montenegro et al. (2006). These estimate travel
times of 95 to 220 days (assuming a journey from
Iberia to North America), and are a function of
boat speed and the fact that dominant mid- to highlatitude
winds in the North Atlantic are westerly
(i.e., opposed to the proposed direction of travel)
and were strengthened during the LGM. Although
these models are by necessity simplifications
of reality, they do provide a first approximation of
the time duration involved, which even at the lowest
estimate, is 1.5–3 times greater than the amount
of time for which seasonal ice was present in the
central and northeastern Atlantic. The implication
is that by the time a group of hunters had reached
the Central Atlantic, the connection to the Americas
may already have been broken.
Implications for the Trans-Atlantic Crossing:
Nature of the Ice-Edge Corridor
From the previous section, it is clear that only
short intervals coinciding with the Solutrean were
characterized by large expanses of ice. Nonetheless,
even if it is assumed that this constituted suffi cient
ice to allow a crossing, or that it took place during
Heinrich Events 1 or 2, there is an additional aspect
to consider: whether the ice-edge corridor was
actually amenable to migration. This revolves heavily
around questions of productivity. Did suffi cient
marine resources exist to allow the development of
a Solutrean maritime adaptation, attract it across the
ocean, and then sustain it along the way?
Bradley and Stanford (2004:469) assert this was
indeed the case, describing both the Bay of Biscay
and ice-edge corridor as “a region with intense biological
productivity, providing a major food source
for much of the marine food chain.” Their suggestion
is based on three lines of evidence:
1. Enhanced photosynthesis of Arctic and
sub-Arctic species of plankton caused by
their shift to lower latitudes.
2. Increased LGM productivity resulting from
the erosion of “seabed ooze” from exposed
continental shelves, increased loess deposition
and upwelling of intermediate
waters caused by more vigorous atmospheric
circulation, and increased mineral
input derived from ice rafted minerals.
3. The ice-edge is a region of intense biological
productivity.
In fact, each of these mechanisms is less straightforward
than described above and includes several
features that weaken the hypothesis. Taking the fi rst
of the lines of evidence, the shift of Arctic and
sub-Arctic plankton to lower latitudes may not
necessarily have increased photosynthesis per se.
It may have been more a case of spreading it more
2008 K. Westley and J. Dix 93
ments, resources either cluster at the ice edge or in
polynyas (open water spaces) (e.g., Henshaw 2003).
What is less clear is whether this high productivity
should be considered in a relative sense—i.e., the
ice edges were more productive than the surrounding
ice itself, but were they more productive than
coastlines and inland areas? Additionally, whether
or not this level of productivity was maintained
across the Atlantic is another matter, largely due to
the fact that the ocean is not a uniform environment.
Simply put, the ice corridor had to cross the open
ocean, an environment that tends to be characterized
by lower productivity than coastal areas and
continental shelves, on account of increased water
depths inhibiting the suspension of seabed nutrients
by waves and tides and the increased distance to
coastal nutrient sources (e.g., rivers). Admittedly,
the North Atlantic is characterized by a band of high
productivity created by a spring/summer plankton
bloom that is presently situated between 45–55°N.
Nevertheless, we should note the fact that this
bloom would have been initiated during or after
the ice melt (especially considering the duration of
LGM ice extents described in section 2) and may
also have shifted over time. Villanueva et al. (2001),
for example, suggest that band had moved south to
37°N during the period in question, in other words
away from the hypothesized ice-edge. Together with
the evidence for reduced areas of productive shallow
shelf at times of low sea-level (see above), this
strongly suggests that all but the very beginning and
end of the hypothesized dispersal took place over
low productivity deep water. In short, an assumption
of a much more spatio-temporally dynamic system
of productivity is no less valid than one of constant
high productivity. Therefore, even if its starting
point was characterized by a highly productive ecosystem,
it is an open question whether the rest of the
route was characterized by a corridor of similarly
productive ecosystems. Without this incentive, it is
more likely that sea-ice based hunters stayed in productive
coastal waters rather than venturing across
the less productive deep ocean.
Aside from issues of productivity, there is a fi nal
crucial point to examine in our consideration of the
hypothetical dispersal route: its end point. In this
case, the question is, once across the Atlantic bridge,
what landscape would the migrants have faced and
would it have induced them to stay or even return
on successive voyages? After all, the colonization of
the Americas and direct link between Clovis and the
Solutrean would have required an incoming population
to stay and expand. Assuming the dispersal
followed the ice-edge, the landing point on North
America was the perennial ice which existed off the
eastern Canadian coast—more specifi cally off Newfoundland
and Labrador—coincidentally the parts
productivity. It should be noted that this mechanism
seems to have been particularly apparent during
Heinrich Event 1 in the 40–50°N latitudinal band
(i.e., the same latitude as the Bay of Biscay; Nave
et al. 2007). Thirdly, mineral input requires the icebergs
to melt so as to release the IRD they carry and
consequently increased productivity (if not offset by
the aforementioned mechanisms) only occurred at
certain times of the year, creating a highly seasonal
system rather than overall heightened productivity
levels. In short, the times of greatest ice, when a seaice
based adaptation might be expected to develop,
seem to have been some of the least productive.
The role of eroded seabed ooze during sea-level
lowstands is a similarly questionable mechanism,
since the delivery of sediment eroded from land is
a feature that enhances coastal productivity during
both low- and highstands. Why this process is
regarded as being of greater importance during the
LGM is unclear. If the crucial factor is taken to be
the erosion of “seabed ooze” rather than terrestrial
sediment, then it is worth considering the fact that
it was more common for shelves to be exposed than
submerged during the last glacial. Thus, maximum
shelf inundation and deposition of “seabed ooze” occurred
during Marine Isotope Stage 5e (≈125 cal ka
BP). Subsequently, global sea-levels fell, staying below
-40m for most of the next 100,000 years. From
50 cal ka BP on, sea-levels oscillated around the -80
to -90m mark before falling to the LGM lowstand of
≈120m by 27–26 cal ka BP (Peltier and Fairbanks
2006, Siddall et al. 2003). This pattern suggests that
by the time of the Solutrean, much of the deposited
ooze may have already been eroded out and replaced
on the subaerial shelf by terrestrial sediment. Moreover,
there is an additional complication concerning
the role of continental shelves in generating productivity—
namely the fact that they are the most productive
parts of the marine ecosystem. Their shallow
depth allows sunlight to reach the seabed, promoting
the growth of productive marine plant communities,
and also permitting waves and currents to suspend
nutrients from the seabed and transport them to the
photosynthetic zone. They also play an important
role as nurseries for a number of pelagic species
(Mann 2000). It might therefore be expected that the
reduction of shallow subtidal shelf areas by sea-level
fall led to decreased productivity, or at the very least
offset some of the other hypothesized productivityincreasing
mechanisms put forward by the Solutrean
Atlantic Hypothesis.
Finally, regarding the third argument for high
productivity, there is no doubt that the ice-edge is
a productive environment. After all, areas under ice
are light limited and hence experience reduced primary
productivity levels (see above and Smetacek
and Nicol 2005). Consequently, in Arctic environ94
Journal of the North Atlantic Volume 1
However, both events were characterized
by low marine productivity, which in turn
argues against a marine-based migration.
Moreover, a migration during Heinrich 2
increases the time gap between Solutrean
and Clovis assemblages to 10,000 years,
while the Solutrean overlap with Heinrich
1 is minimal, i.e., very few Solutrean sites
actually date to 17–18 cal ka BP.
3. The pattern of LGM ice cover raises the
possibility that the annual ice melt pattern
may not have been synchronous across the
North Atlantic. More specifi cally, an icefree
channel in the central Atlantic may
have expanded, splitting the ice-edge. If
Solutrean hunters were indeed following
it, they were more likely to move north
than west across the Atlantic.
4. Dominant wind and current patterns
were against the direction of dispersal.
Although overcoming them was not impossible
(i.e., by paddling or sailing), it
would have increased the journey times
making it less likely that any migrants
would have reached the central Atlantic
while the ice-edge there was intact.
5. Consistently high marine and ice-edge
productivity should be regarded as a possibility
not as a given. There is no doubt
that marine resources existed in the Bay of
Biscay and all along the exposed Atlantic
margin. However, the main contention is
that evidence for the level of productivity
advocated by Bradley and Stanford
(2004), particularly in deep ocean waters
that characterized the vast majority of the
hypothesized dispersal route, is simply not
there. The well-documented dynamism of
Late Pleistocene climate in conjunction
with the sensitivity of a sea-ice based
ecosystem is more likely to have resulted
in much more variable productivity levels
across both space and time. Although this
can be argued to have been a driver for
movement (i.e., migration in response
to movement of prey), it can equally be
regarded as a barrier (i.e., areas of low
productivity inhibit dispersal).
6. Any migrants that made it across the
hypothetical ice-edge corridor were confronted
by a very different landscape to
the one they had left, specifi cally one
dominated by a continental ice sheet. This
environment was a harsh and potentially
unproductive landscape (certainly for the
areas of exposed land), and we question
whether there would have been any desire
to stay.
of North America closest to Europe, as Bradley and
Stanford (2006) point out. During the LGM, the vast
majority of this area was covered by the Laurentide
ice sheet with the exception of fringing areas of icefree
continental shelf exposed by glacial forebulge
uplift and lowered glacio-eustatic sea-levels, such
as the Grand Banks southeast of Newfoundland
(Fig. 1; Shaw et al. 2002). These however were
spatially quite restricted as the ice sheet extended
out to the shelf edge across most of eastern Canada.
By 21 cal ka BP, it had begun to break up, and it
was not until ≈19–17 cal ka BP (i.e., the end of the
Solutrean) that areas of shelf were ice-free (Shaw et
al. 2006). Indeed, Shaw (2005) explicitly points out
that this view contrasts with the image of emergent
shelves depicted by Bradley and Stanford (2004:
Fig. 4). Moreover, during and immediately after
deglaciation, exposed shelves may have been isostatically
depressed by the former weight of ice,
and therefore initially fl ooded as the ice retreated.
At this time, the mainland (i.e., presently terrestrial
areas) was also still under ice and unavailable for
settlement by incoming populations. Effectively,
any migrants would have either been restricted to
small isolated areas of exposed low-lying shelf. Further,
the environment of these exposed shelf areas
is also uncertain. Were they glacial refugia, such as
have been found on the Pacifi c Northwest coast, or
did their low topography make them areas of polar
desert swept by intensely cold winds coming off the
Laurentide ice, and susceptible to the glacio-eustatic
rise in sea-level that was beginning at that time (Peltier
and Fairbanks 2006)? Either way they presented
a quite different landscape from the Bay of Biscay
where hundreds of kilometres of open unglaciated
terrain with both coastal and inland resources were
readily available.
Synthesis and Conclusion
The information above reveals a number of obstacles
to the hypothesized migration, specifi cally
concerning the mechanism of dispersal: movement
along the edge of the sea-ice in the North Atlantic.
These can be summarized as follows:
1. There was less sea-ice at the LGM than
commonly believed, with large zones
of the North Atlantic and, in particular,
the Bay of Biscay experiencing less than
1–2 months of sea-ice per year on average.
Thus, we question whether suffi cient ice
existed to permit the development of an
intensively ice-based subsistence strategy
or to allow hunters to travel all the way
across the Atlantic within a single year.
2. The greatest ice extents of the Late Pleistocene
took place at Heinrich Events 1 and 2.
2008 K. Westley and J. Dix 95
To conclude, it is clear from the paleoceanographic
and paleo-environmental data that the LGM North
Atlantic does not fi t the descriptions provided by the
proponents of the Solutrean Atlantic Hypothesis. Although
ice use and sea mammal hunting may have
been important in other contexts, in this instance, the
conditions militate against an ice-edge-following,
maritime-adapted European population reaching the
Americas. The approach and data described in this
paper are relevant not only in the specifi c case, but
also on a wider scale. For paleo-coastal societies, the
nature of the offshore environment is as important
as the onshore; hence, knowledge of the state of the
oceans is critical to our archaeological understanding.
This fact is particularly signifi cant given that
archaeological work has been consistently pushing
the onset of coastal/marine resource use back into
the Pleistocene (e.g., Marean et al. 2007), a period
characterized by ever-increasing quantities and resolution
of paleo-environmental data that show an array
of environmental changes, often of large magnitude,
operating both on land and at sea. Archaeologists
should therefore be prepared to engage as much
with the paleo-environmental and paleoceanographic
records as with more conventional archaeological
data. This conclusion does not necessarily mean
that they should independently collect or generate
the relevant data, but rather should be aware of its
existence, be able to understand and integrate that
information with the archaeological record in an effort
to attain a more balanced view of prehistory.
Acknowledgments
This research was undertaken as part of a Ph.D. conducted
at Southampton University and was supported
fi nancially by a Richard Newitt bursary. Additional support
was provided by English Heritage via Aggregate Levy
Sustainability Fund Grant 3362. Constructive comments
and criticisms on the draft were provided by Ruth Plets,
Frédérique Eynaud (who is also thanked for the paleoceanographic
data for the Bay of Biscay), and two anonymous
reviewers. Thanks also go to William Davies and Clive
Gamble for use of the S2AGES database.
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