Quaternary Science Reviews 85 (2014) 35e46
Contents lists available at ScienceDirect
Quaternary Science Reviews
journal homepage: www.elsevier.com/locate/quascirev
Northeastern North American Pleistocene megafauna chronologically
overlapped minimally with Paleoindians
Matthew T. Boulanger a, b, *, R. Lee Lyman a
a
b
Department of Anthropology, 107 Swallow Hall, University of Missouri, Columbia, MO 65211, USA
Archaeometry Laboratory, University of Missouri Research Reactor, 1513 Research Park Drive, Columbia, MO 65211, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 8 May 2013
Received in revised form
26 November 2013
Accepted 28 November 2013
Available online
It has long been argued that specialized big-game-hunting Paleoindians were responsible for the
extinction of three dozen large-bodied mammalian genera in North America. In northeastern North
America, the overkill hypothesis cannot be tested on the basis of associations of Paleoindian artifacts and
remains of extinct mammals because no unequivocal associations are known. The overkill hypothesis
requires Paleoindians to be contemporaneous with extinct mammalian taxa and this provides a means to
evaluate the hypothesis, but contemporaneity does not confirm overkill. Blitzkrieg may produce evidence
of contemporaneity but it may not, rendering it difficult to test. Overkill and Blitzkrieg both require large
megafaunal populations. Chronological data, Sporormiella abundance, genetics, and paleoclimatic data
suggest megafauna populations declined prior to human colonization and people were only briefly
contemporaneous with megafauna. Local Paleoindians may have only delivered the coup de grace to
small scattered and isolated populations of megafauna.
Ó 2013 Elsevier Ltd. All rights reserved.
Keywords:
Extinction
Megafauna
North America
Paleoindian
Radiocarbon
1. Introduction
During the late Pleistocene, North America lost 36 genera of
mammals, most of them (N ¼ 30) large-bodied (44 kg). Thirty
genera went globally extinct, but the remainder survived elsewhere
(Grayson, 2011). Paleontologists and archaeologists have debated
the causes of these extinctions for decades (Grayson, 1980, 1984a),
with purported growing consensus on a single cause an illusion
(Barnosky et al., 2004; Grayson, 2006, 2007; Koch and Barnosky,
2006; Surovell, 2008; Ripple and Van Valkenburgh, 2010). The
most popular causes are overkill by humans (Wesler, 1981; Fiedel
and Haynes, 2004; Martin, 2005; Surovell et al., 2005; Haynes,
2007, 2009; Surovell and Waguespack, 2009) and environmental
change of one sort or another (Graham and Lundelius, 1984;
Guthrie, 1984; Haynes, 2008; Nogués-Bravo et al., 2010). A hyperdisease has also been suggested as the cause (MacPhee and Marx,
1997), but no known diseases have the properties necessary to
wipe out genetically unrelated genera (e.g., Lyons et al., 2004). A
recently proposed extraterrestrial impact at 12,900 BP (Firestone
et al., 2007) as the cause has been extensively questioned
* Corresponding author. Department of Anthropology, 107 Swallow Hall, University of Missouri, Columbia, MO 65211, USA.
E-mail addresses: [email protected], [email protected] (M.
T. Boulanger).
0277-3791/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.quascirev.2013.11.024
(Buchanan et al., 2008; Marlon et al., 2009; Surovell et al., 2009b;
Daulton et al., 2010; Haynes et al., 2010; Pigati et al., 2012), and
we do not consider it here.
Studies examining the chronologies of Pleistocene extinctions
and Paleoindian arrivals into the North American continent have
tended to adopt a continent-wide perspective (e.g., Buchanan et al.,
2008; Haynes, 2008). Yet, these large-scale studies tend to be
biased by the rich paleontological and archaeological records of
western North Americadspecifically the Great Plains and American
Southwestdrelative to that of eastern North America (Meltzer,
1988; Lepper and Meltzer, 1991). Moreover, although continentwide studies provide general views of historical events, they
diminish resolution and mask details that may have important
bearing on regional issues. Just as the history of a fauna can be
understood only through the histories of individual species
composing that fauna (Grayson, 2007), so too the history of
continent-wide extinctions can be understood only through the
extinction histories of individual regions (e.g., Lima-Ribeiro and
Diniz-Filho, 2013). This issue of scale is commonly acknowledged
in modern ecology and evolution (e.g., Landres, 1992; Callicott,
2002; Frankham and Brook, 2004; Berkes, 2006), and we view
extinction, regardless of its cause(s), as an ecological and evolutionary process.
Here, we adopt a fine-scale approach to the question of human
involvement in the extinction processes of Pleistocene megafauna
in northeastern North America, defined here as the New England
36
M.T. Boulanger, R.L. Lyman / Quaternary Science Reviews 85 (2014) 35e46
The chronology of extinctions is critical to deciphering their
cause (Grayson, 2007; Faith and Surovell, 2009; Fiedel, 2009). If all
36 genera went extinct at approximately the same time (within,
say, 500e1000 years), that will have implications for cause that are
different than those suggested by the 36 genera going extinct over,
say, 5000, or 10,000 years (Martin, 1986; Fiedel, 2009). Chronology
is also critical to the overkill hypothesis because remains of prehistoric people and remains of the extinct megafauna must, at a
minimum, be contemporaneous. If there is no evidence that
humans and extinct fauna were contemporaries, then the overkill
hypothesis could not be sustained. If the two are contemporaries,
overkill would not be confirmed but neither would it be refuted
(e.g., Haynes and Stanford, 1984; Lima-Ribeiro and Diniz-Filho,
2013).
When Paul Martin originally outlined the overkill hypothesis, he
advocated human hunting as the singular cause of the terminal
Pleistocene extinctions. His major line of evidence for the overkill
hypothesis was the apparent contemporaneity of the appearance of
Paleoindians in North America and the extinctions (Martin,
1966:342; 1967:75, 115; 1973:969; 1974:680; Mosimann and
Martin, 1975:304). Lack of contemporaneity of the two events
would falsify the original overkill hypothesis. The test implications
of Martin’s hypothesis are (i) the two phenomena must be
contemporary, and (ii) populations of megafauna must be large and
not in decline when humans first appear on the landscape. The
latter rests in Martin’s belief that only humans were responsible for
the extinction rather than, say, a combination of environmental
change and human predation.
When faced with the fact that there were few documented
direct associations of humans and extinct megafauna and few kill
sites, Martin (1973:969) proposed the “Blitzkrieg” version of the
overkill hypothesis: “Extinction [that is, Blitzkrieg overkill] would
have occurred before there was opportunity for the burial of much
evidence by normal geological processes. Poor paleontological
visibility would be inevitable”. Using estimates of the rate of kill site
creation (with no empirical or theoretical warrant) and their
resulting (exceedingly low) density on the landscape, Martin
(1973:974) concluded “it is clear that the probability of the field
evidence actually being detected and appreciated by the discoverers of the bones is small.”
Martin and Steadman (1999:34) later noted the Blitzkrieg model
“accommodates a tight chronology, with no more than a few
hundred years of overlap between human colonization and
megafaunal extinction within the United States and as little as a
decade of overlap of extinct fauna and first colonists in any one
region.” The test implications of Blitzkrieg are (i) contemporaneity,
or (ii) no evidence of contemporaneity given (a) the real-time
brevity of overkill, (b) the resolution of radiocarbon dating, and
(c) the low probability of finding and dating the last of the megafauna and the oldest archaeological material. Blitzkrieg is quite
difficult to test because both its occurrence and its non-occurrence
can produce no evidence of the contemporaneity of humans and
megafauna (Grayson, 1984b).
Although there are no megafauna kill sites in the Northeast,
there is no scarcity of terminal Pleistocene megafauna. Remains of
at least 140 individual mastodon and 18 mammoths have been
recovered in New York alone (Hartnagel and Bishop, 1922; Fisher,
1955; Thompson et al., 2008). A 2009 compilation prepared at
the Earth Sciences Museum University of Waterloo contains records
of 160 proboscidean finds in southern Ontario.2 Other sites and
remains of other taxa are known elsewhere. In the Northeast it
seems highly likely that neither poor preservation of the remains of
extinct mammalian genera nor sampling error has created a lack of
evidence of contemporaneity.
Finally, Martin (1967:102) indicated “clear-cut cases of massive
unbalanced Pleistocene extinction before man [appears]” would
falsify overkill. Evidence of population depletion followed chronologically by human appearance would accommodate some
contemporaneity of the two, and suggest people delivered the coup
de grace to megafaunal populations that were on the verge of
extirpation. This hypothesis accommodates the view of researchers
who favor a middle ground in which both human hunting and
1
All dates cited in text are calibrated using IntCal13 (Reimer et al., 2013) and
given as the mean of the areas of highest probability at the two-sigma level.
2
Available on-line at https://uwaterloo.ca/earth-sciences-museum/life-earth/
ice-age-mammals. Last accessed February 15, 2013.
states and neighboring states of New York, New Jersey, and Pennsylvania, and adjacent portions of the provinces of Quebec and
Ontario in Canada. Though several purported associations of
megafauna remains with human material culture have been reported from this region, none of these has provided unequivocal
evidence of human predation on megafauna despite over 100 years
of archaeological and paleontological research. In spite of this
absence of evidence, and perhaps a bit because of it, the belief that
Paleoindians hunted megafauna has assumed the qualities of an
“almost romantic myth” (Dent, 1991:37). That is, it has become a
proposition that is either directly or indirectly asserted, but as yet
has not been directly evaluated (e.g., Dragoo, 1976:9; Haviland and
Power, 1994:28; Lake, 2003:35; Wiseman, 2001:20e23). Straightforward testing of human hunting of megafauna has been difficult
for want of uncontested associations of megafauna and Paleoindians. Here we examine the viability of the overkill hypothesis
through analysis of available chronometric evidence for contemporaneity of humans and extinct megafauna.
2. Background
The overkill hypothesis, first described by Martin (1967, 1973),
continues to have advocates (e.g., Surovell et al., 2005; Surovell and
Waguespack, 2008; Fiedel, 2009; Haynes, 2009) and naysayers
(e.g., Grayson and Meltzer, 2002, 2003, 2004; Grayson, 2007;
Nagaoka, 2012). Because terminal ages of some genera indicate
they went extinct at approximately the same time, some analysts
argue that all genera went extinct simultaneously (e.g., Haynes,
2008; Fiedel, 2009). Though certainly possible, the age of extinction of more than half the genera is unclear, perhaps because of
sampling error (Faith and Surovell, 2009). Models suggest humans
(e.g., Mosimann and Martin, 1975; Alroy, 2001; Brook and Bowman,
2004) or climate (e.g., Nogués-Bravo et al., 2010) could have caused
the extinctions, but the prehistoric record must be the final arbiter
of timing as well as of cause (Grayson, 2007; Wolverton et al.,
2009).
Simulations (e.g., Mosimann and Martin, 1975) and empirical
data (e.g., Hamilton and Buchanan, 2007; Waters and Stafford,
2007; Haynes, 2008; Fiedel, 2009) imply rapid human colonization of North America. Northeastern North America is believed to
have been colonized late relative to more western areas (Ellis et al.,
1998; Hamilton and Buchanan, 2007; Waters and Stafford, 2007;
Faught, 2008; Ellis, 2011; Miller and Gingerich, 2013). The mean
age of 10,900 14C YBP (12,800 cal BP1) for Clovis (Waters and
Stafford, 2007) is older than all but one northeastern Paleoindian
site: ShawneeeMinisink in southern Pennsylvania (Gingerich,
2007a, 2007b, 2011).
3. Hypotheses
M.T. Boulanger, R.L. Lyman / Quaternary Science Reviews 85 (2014) 35e46
37
Table 1
Radiocarbon dates obtained directly on megafauna skeletal material recovered in Northeastern North America and used to construct SPD curves. All dates calibrated using
IntCal13 and CalPal Advanced, and given at the two-sigma range. Pooled means calculated in Calib, critical values given at 0.05 significance level. Full data on each radiocarbon
assay are presented in Supplementary Information Table 1 (SI 1) and available from the senior author on request.
Lab no.
Dated material
14
1
2
3
4
5
6
7
7
8
CAMS-12587
OS-73632
GX-26619
UGAMS-13936
BETA-141061
I-11286
n/a
OS-68051[B]a
GSC-1220
GSC-1220-2
Tooth (Collagen)
Bone (Collagen)
Bone (Collagen)
Antler (Bioapatite)
Bone (Collagen)
Bone (Collagen)
Bone (Collagen)
Bone (Collagen)
Bone (Collagen)
Bone (Apatite)
Cinmar Mastodon, Atlantic Ocean
Frankstown Cave, Blair Co., PA
Chemung River Valley, Bradford Co., PA
Sparta Mastodon, Sussex Co., NJ
Sparta Mastodon, Sussex Co., NJ
9
10
11
12
UCIAMS-53545
PITT-491
Y-2619
GX-5742[B]
GX-5742[A]
Tusk (Collagen)
Bone (Collagen)
Bone (Whole)
Bone (Collagen)
Bone (Apatite)
Borodin Mastodon, NJ
Delaware, ON
Near Goshen, Orange Co., NY
Near Goshen, Orange Co., NY
13
14
7
GX-25818
AA-84998
n/a
n/a
Bone (Collagen)
Bone (Collagen)
Tusk (Collagen)
Tusk (Collagen)
Tunkamoose Mastodon, Orange Co., NYb
Tunkamoose Mastodon, Orange Co., NYb
7
OS-78281
OS-78282
Tusk (Collagen)
Tusk (Collagen)
Norfolk, ON
Arborio Mastodon, Orange Co., NY
Pirrello Mastodon, Wayne Co., NYc
North Java, Wyoming Co., NY
Fairview Mastodon, Livingstone Co., NY
Perkinsville Mastodon, Steuben Co., NY
Hyde Park Mastodon, Dutchess Co., NY
Doerfel, Erie Co., NY
Ivory Pond, Berkshire Co., MA
Thamesville Mastodont
Hiscock, Genesee Co., NY
Caradoc, ON
Cohoes Mastodon, Albany Co., NY
Mastodon, Atlantic Ocean
Hiscock, Genesee Co., NY
Hiscock, Genesee Co., NY
Hiscock, Genesee Co., NY
15
7
16
17
18
19
20
21
22
23
24
25
26
27
24
24
24
AA-84989
OS-93884
OS-93338
BETA-176928d
AA-7397
OS-93357
BETA-135234
CAMS-54734
GX-9024G
GSC-611
AA-6977
AA-84980
n/a
AA-1506
CAMS-30528
CAMS-30529
GX-22038
Tooth (Collagen)
Tooth (Collagen)
Bone (Collagen)
Bone (Collagen)
Bone (Collagen)
Tooth (Collagen)
Tusk (Collagen)
Bone (Collagen)
Bone (Collagen)
Bone (Collagen)
Bone (Collagen)e
Bone (Collagen)
Bone (Collagen)
Tooth (Collagen)
Ivorye,f
Ivorye,f
Ivorye,f
Bojak Mastodon, Warren Co., NJ
Hiscock, Genesee Co., NY
Temple Hill Mastodon, Orange Co., NY
Temple Hill Mastodon, Orange Co., NY
28
24
29
GX-2675
TO-3194
OS-93337
NZA-12584
Bone (Collagen)
Bone (Collagen)
Tooth (Collagen)
Bone (Collagen)
Ellenville Mastodon, Ulster Co., NY
Hiscock, Genesee Co., NY
Watkins Glen Mastodon, Schuyler Co., NY
Hiscock, Genesee Co., NY
Hiscock, Genesee Co., NY
Hiscock, Genesee Co., NY
Hiscock, Genesee Co., NY
Newton/Spring Lake, Bradford Co., PA
Moon Mammoth, Erie Co., PA
Scarborough, Cumberland Co., ME
Scarborough, Cumberland Co., ME
Scarborough, Cumberland Co., ME
30
24
31
24
24
24
24
32
33
34
OS-94876
NZA-1106
BETA-176930
CAMS-62560
CAMS-27143
CAMS-17407
BETA-24412
WIS-1935
BETA-49776
CAMS-54733
OS-5636
AA-8215A
Bone (Collagen)
Bone (Collagen)
Bone (Collagen)
Bone (Collagen)
Bone (Collagen)e
Bone (Collagen)
Bone (Collagen)
Bone (Collagen)
Bone (Collagen)
Bone (Collagen)
Tooth (collagen)
Tusk (Collagen)
Muirkirk Mammoth, ON
Muirkirk Mammoth, ON
Muirkirk Mammoth, ON
35
GRA-22177
GRN-28020
GRN-28022
Bone (Collagen)
Bone (Collagen)
Tusk (Collagen)
Clyde Barge Canal, Wayne Co., NY
Chittenango Mammoth, Madison Co., NY
Berry Mammoth, Atlantic Ocean
Watkins Glen Mammoth, Schuyler Co., NY
Rostock Mammoth
Randolph Mammoth, Cattaraugus Co., NY
2
36
37
31
38
39
OS-85534
OS-93430
AA-1505
BETA-176929
WAT-999
OS-93354
Tooth (Collagen)
Tusk (Collagen)
Tooth (Collagen)
Bone (Collagen)
Tusk (Collagen)
Tooth (Collagen)
11670
10150
23530
12370
12180
11230
11040
10800
32000
31300
31570
22760
13740
13320
12730
12320
12550
12510
12360
12300
12350
12325
12350
12300
12320
11820
11750
11700
11630
11565
11500
11480
11460
11440
11380
11390
11120
11070
11070
11100
11070
10930
11030
10995
10990
10900
11000
10920
10850
10850
10840
10810
10790
10630
10515
14240
12210
12160
12200
12720
12190
12130
12180
12250
12190
11750
11250
10930
10890
10790
10350
70
50
170
25
60
160
110
45
630
500
390
90
145
200
360
410
270
180
120
45
45
30
65
45
40
120
60
40
60
105
45
60
60
655
170
80
110
60
130
80
70
70
40
750
100
40
80
40
45
140
60
50
70
80
120
150
120
50
55
250
40
80
70
70
40
65
65
315
50
150
45
Genera
Specimen
Castoroides
Dutchess Quarry Cave 8, Orange Co., NY
Clyde, Wayne Co., NY
Manasquan Inlet, NJ
Big Brook Locality, Monmouth Co., NJ
Pawelski Farm, Orange Co., NY
Columbia Stag Moose, Warren Co., NJ
Near Goshen, Orange Co., NY
Orange Co., NY
Lower Middle River
Lower Middle River
Cervalces
Mammut
Mammuthus
Location
(Fig. 1)
C YBP
t
Critical
value
Cal BP
13640e13360
12070e11550
27920e27440
14680e14120
14220e13900
13410e12730
13130e12690
12750e12670
0.757
3.84, 1
36290e34650
27400e26840
17080e16160
16560e15440
0.565
3.84, 1
15690e13810
15410e13970
15010e13930
0.617
3.84, 1
14510e14070
0.4
3.84, 1
14540e14060
13890e13410
13770e13410
13600e13440
13600e13320
13600e13200
13450e13250
13470e13190
13440e13160
15130e11810
13560e12920
13390e13070
13200e12720
13110e12750
13170e12690
3.129
5.99, 2
13040e12760
14640e10760
13100e12660
1.25
3.84, 1
12860e12700
12800e12680
13050e12530
12820e12660
12780e12660
12780e12620
12760e12400
12770e12010
17740e16900
14670e13710
4.887
5.99, 2
14200e13960
1.316
5.99, 2
14200e13960
13770e13410
13240e13000
13430e12110
12840e12680
12990e12430
12460e11980
(continued on next page)
38
M.T. Boulanger, R.L. Lyman / Quaternary Science Reviews 85 (2014) 35e46
Table 1 (continued )
Genera
Specimen
Location
(Fig. 1)
Lab no.
Dated material
14
Ovibos
Platygonus
Elizabethtown Musk Ox
Dutchess Quarry Cave 8, Orange Co., NY
Dutchess Quarry Cave 8, Orange Co., NY
Dutchess Quarry Cave 8, Orange Co., NY
40
1
1
1
AA-4935
CAMS-12592
CAMS-13027
CAMS-13057
Bone (Collagen)
Tooth (Collagen)
Tooth (Collagen)
Tooth (Collagen)
Wyoming Co., NY
Camburn Elephant, Monmouth Co., NJ
41
42
OS-68051[A]a
GX-18789
Bone (Collagen)
Bone (Collagen)
11362g
12430
12220
12160
12200
10750
12470
115
70
60
80
50
50
260
Proboscidean
C YBP
t
Critical
value
Cal BP
13440e13000
14990e14110
0.36
3.84, 1
14230e13950
12740e12620
15530e13770
**
Reporting authors recommend averaging these two dates alone, although AA-8215A (12720 þ/ 250) is statistically identical.
Duplicate laboratory numbers given in same publication. Authors note of the Cervalces specimen: "This specimen is likely the same specimen previously dated by Buckley
and Willis (1970) and reported by Funk et al. (1970) as the C. scotti (NYSM 24123) from the Dewey Parr locality (I-4016).” Specimen I-4016 (10950 þ/ 150 14C YBP) was
excluded from our analyses but the date is statistically identical to this more-recent assay (t ¼ 0.917, c2(.05, 1) ¼ 3.84).
b
Specimens derive from the same locality, and dates are statistically identical; however, reporting authors make no mention of the possibility that they derive from the
same mastodon individual. Here, we adopt a conservative approach and treat the two specimens as representing the same individual.
c
An assay conducted on this same individual at some point prior to 1974 is reported by Reilly (1974) and returned a date of 10340 þ/ 170 14C YBP(no laboratory number
provided). We prefer the more-recent AMS assay reported bydand also preferred bydFeranec and Kozlowski (2012).
d
Hodgson and colleagues in the abstract of their paper in the same volume in which this date is published list this assay as 11560 þ/ 60. We use the date as given by Griggs
and Kromer (2008) because (1) their chapter explicitly deals with analysis of radiocarbon dates from this site, and (2) by cross-reference to other published accounts of this
date.
e
Reporting authors (Tankersley et al., 1998) do not explicitly identify this specimen as mastodon bone; however, see McAndrews (2003) and Laub (2003).
f
Three assays on same specimen of ivory. See McAndrews (2003) and Laub (2003).
g
Rayburn et al. (2007) correct the original AMS date using an estimated 13C value.
a
climatic change were important but individually partial causes
(Barnosky et al., 2004; Koch and Barnosky, 2006; Nikoloskiy et al.,
2011). But again, evidence of contemporaneity does not mean
people had a causal hand in the extinction process; rather, it only
indicates they could have.
4. Materials and methods
Northeastern North American Paleoindian peoples are identified
by diagnostic fluted and unfluted stone lanceolate bifacial tools (Ellis
et al., 1998; Newby et al., 2005; Bradley et al., 2008; Lothrop et al.,
2011). Extinct megafauna are defined as mammalian taxa with
estimated body masses exceeding 44 kg that have been either
regionally or globally extinct since the PleistoceneeHolocene transition, ca 11,000e10,000 14C YBP (12,800e11,500 cal BP). Taxa
meeting this definition include mastodon (Mammut sp.), Scott’s
stag-moose (Cervalces scotti), mammoth (Mammuthus sp.), giant
beaver (Castoroides ohioensis), musk ox (Ovibos moschatus), flatheaded peccary (Platygonus compressus), and Steppe bison (Bison
priscus [formerly B. crassicornis]). Caribou (Rangifer tarandus) were
present in the Northeast during the Pleistocene and would qualify as
megafauna but they are excluded here because historical, archaeological, and paleoecological data indicate they persisted in the region throughout the Holocene until being locally extirpated during
the twentieth century (Goodwin, 1936; Palmer, 1938; Guilday, 1968;
Bergerud, 1974; Bergerud et al., 2008; Putnam and Putnam, 2009).
4.1. Chronometric data
We first consulted radiocarbon databases, including FAUNMAP
II (Graham and Lundelius, 2010), CARD (Morlan, 1999; Gajewski
et al., 2011), Harington’s (2003) compilation, and state-level databases (Jordan, 1969; Herbstritt, 1988; Hoffman, 1988; Levine, 1990;
Gengras, 1996; Cox, 1999; Reeve and Forgacs, 1999; Will, 1999;
Boulanger, 2007; Public Archaeology Laboratory, 2010). We then
consulted primary sources to identify errors (e.g., compare dates for
Michaud in Spiess and Wilson [1987] with those in Lothrop et al.,
[2011]). Recent literature was consulted to ensure inclusion of
dates that had appeared since the compilation of radiocarbon databases, and regional archaeologists and paleontologists were
queried for as-yet unreported dates. Finally, one AMS date obtained
by the authors during this study is included and reported here for
the first time.
4.1.1. Megafauna database
We identified a total of 115 radiocarbon determinations associated with Pleistocene megafauna in the Northeast. This database
was then vetted using a modified version of the criteria advocated
by Barnosky and Lindsey (2010: Table 1) to increase confidence that
the measured variabledthe calibrated (radiocarbon) agedaccurately reflects the target variabledthe date when an animal
died. Unlike Barnosky and Lindsey, we included assays performed
on bone apatite when isotopic or complementary 14C analyses
indicated that contamination is not evident.
Our vetting protocol resulted in the elimination of 46 dates
(Supplementary Information [SI] 2), leaving 69 individual assays in
our sample (SI 1). Two or more radiocarbon assays were reported
for nine individual specimens in our database. To eliminate undue
influence of multiple dates on the same megafauna specimen, we
subjected the dates to a chi-square test of significance using Calib
v.6.0.1 (Stuiver and Reimer, 1993). Dates from an individual megafauna specimen determined to be statistically identical at the 95%
confidence interval were combined into pooled means in Calib. No
instances were encountered in our vetted sample of a megafauna
specimen having two or more ranges of dates that were not statistically identical at this confidence interval. Calculation of pooled
means resulted in a final sample size of 57 radiocarbon-dated
specimens from 47 separate localities (Fig. 1), and representing
six different genera (Table 1). More than half of these assays are
obtained on Mammut specimens, and nearly 80% of our sample is of
the order Proboscidea. Thus, our sample is strongly biased towards
proboscideans.
On one hand, we suspect genera not represented in the vetted
sample of dates were absent or quite rare on the Northeast landscape. The abundance of proboscideans, on the other hand, may
reflect their abundance on the landscape, a greater probability of
being dated than remains of other genera, or some other factor.
Nevertheless, we assume the vetted sample reflects at an ordinal
and relative scale the abundance of individuals of the multi-taxon
category “megafauna”.
4.1.2. Paleoindian database
We identified a total of 102 radiocarbon dates reported for
Paleoindian components in the Northeast (SI 3 and 4). Yet, the
quality of this database continues to be a subject of debate. Unlike
direct dates on megafaunal skeletal remains, not all measured dates
from archaeological sites can be reasonably assumed to represent
M.T. Boulanger, R.L. Lyman / Quaternary Science Reviews 85 (2014) 35e46
39
Fig. 1. Paleontological localities and archaeological sites in the American Northeast from which radiocarbon dates are used in this study. Site numbers correspond to those given in
Tables 1and 2.
the target dateda temporal estimation of human presence. There is
no disciplinary consensus as yet on which dates are reflective of
human occupations and which may represent naturally occurring
forest fires (e.g., Levine, 1990; Curran, 1996; Spiess et al., 1998;
Bonnichsen and Will, 1999). Some dates are relatively easily
excluded because of anomalously young ages post-dating any
known Paleoindian component in the Western Hemisphere (e.g., a
calibrated date of AD 1650 115 [I-3443] from West Athens Hill in
New York reported by Ritchie and Funk [1973]). Others can be
rejected based on the absence of, or equivocal associations with,
Paleoindian materials (e.g., BETA-18133 reported by Tankersley
et al., [1997] and Gramly [1988:273] for the Lamb site was obtained on a sample of wood from the basal layer of a peat bog
located over 25 m from the site). Similarly, radiocarbon dates reported from Paleoindian-bearing strata at Hiscock in northwestern
New York (Laub et al., 1988; Laub, 2002) are actually younger than
dates obtained from overlying strata. Based on these results and
examination of faunal and sedimentological data, Steadman (1988)
suggests that strata in this bog are disturbed to such an extent that
suspected associations between the dated organic materials and
Paleoindian artifacts cannot be confirmed (see also Laub, 2003).
Direct dates on purported bone tools from Hiscock cannot be used
either, because current interpretations (Laub, 2002; Tomenchuk,
2003) are that early human populations likely scavenged bones
from the bog, and that animals found there had suffered natural
deathsdand, see Haynes (2002, 2003) who disputes that these are
in fact tools.
In other instances, archaeological sites exhibit multiple populations of differently aged charcoal and/or bone (Levine, 1990;
Bonnichsen and Will, 1999). For example, radiocarbon dates from
Whipple in New Hampshire (Curran, 1984, 1996) were obtained on
charcoal specimens recovered from concentrations of lithic debitage and calcined bone. Though the charcoal was initially assumed
to be cultural, it is now suspected to be evidence of natural burns
(Curran, 1994, 1996). Similarly, a date on charcoal (BETA-1833) from
Feature 1 at Vail returned an age of 11,120 180 14C YBP
(12,990 180 cal BP; Gramly, 2009). This date is considered suspect
(Haynes et al., 1984; Curran, 1996) because four additional assays of
the same charcoal specimen produced a series of ages which are in
statistical agreement with one another, but roughly 1000 years
younger than BETA-1833.
The use of a ranking system for Paleoindian dates, similar to that
used by Barnosky and Lindsey (2010) or Mead and Meltzer (1984),
presents additional problems. For example, recently reporteddand
widely accepteddradiocarbon dates for Bull Brook (Robinson et al.,
2009) would not be acceptable because of the equivocal archaeological context of the specimens and the dating of bone apatite,
whereas the previously mentioned dates from Whipple would be
accepted despite the general consensus that these represent natural forest fires. In order to circumvent these issues, we first ranked
each date according to the criteria of Barnosky and Lindsey (2010)
and then used the primary literature to identify factors that might
give reason to discount the radiocarbon determination as a valid
temporal estimate of archaeological site occupation. All of our
dates, their ranks, and explanations for date rejections are provided
in the Supplementary Material of this article.
Our compiled radiocarbon database is similar to those used by
others in regional analyses (e.g., Newby et al., 2005; Lothrop et al.,
2011; Miller and Gingerich, 2013). Major differences include the
addition of recently obtained dates from two sites, and the elimination of the aforementioned dates from Whipple. Fifty-six individual radiocarbon determinations were selected from 22
Paleoindian components in the Northeast (Fig. 1, Table 2). As with
the megafauna dates, dates from the same archaeological components were evaluated using the Chi-square test in Calib. Two exceptions to the pooled mean process were made. First, three
radiocarbon dates from Feature 1 at Vail in Maine reported by
Haynes et al. (1984) are statistically identical; however, a recently
obtained AMS date reported by Gramly (2009) on the same charcoal specimen is statistically different from these. In this case,
because all of the assays were performed on the same material yet
are significantly different, and no additional modern assays have
40
M.T. Boulanger, R.L. Lyman / Quaternary Science Reviews 85 (2014) 35e46
Table 2
Radiocarbon dates obtained from Paleoindian archaeological sites in Northeastern North America and used to construct SPD curves. All dates calibrated using IntCal13 and
CalPal Advanced and given at the two-sigma range. Pooled means calculated in Calib, critical values given at 0.05 significance level. Full data on each radiocarbon assay are
presented in Supplementary Information Table 1 (SI 3) and available from the senior author on request.
Site
Location
Arc
Brigham (ME90.2C)
Bull Brook
1
2
3
Colebrook (27CO38)
4
Debert (BiCu-1)
5
Dutchess Quarry Cave 8
Esker (ME86.12)
Hidden Creek (72e163)
Hidden Creek (72e163)
6
7
8
8
Janet Cormier (ME23.25)
Jefferson II (27CO29)
Michaud (ME23.12)
9
10
11
Neponset/Wamsutta (19NF70)
Nesquehoning Creek (36CR142)
ShawneeeMinisink (36MR43)
12
13
14
Steel (28CM42)
Templeton (6LF21)
15
16
Turkey Swamp
Vail (ME81.1)
17
18
Varney Farm (1) (ME36.57)
19
Varney Farm (2) (ME36.57)
19
Varney Farm (3) (ME36.57)
Wallis (36PE16)
Weirs Beach (NH26.32)
West Creek (28OC45)
19
20
21
22
a
b
Lab no.
BGS-1794, BGS-1795
BETA-7183
BETA-240629
BETA-240630
BETA-107429
BETA-258579
P-977,
P-743a,
P-970a,
P-972,
P-741a,
P-966a,
P-967a,
P-973,
P-739a,
P-971,
P-974,
P-975
BETA-25255
BETA-103384
BETA-126817
BETA-121846,
BETA-149920
BETA-126645
BETA-108465
BETA-13833,
BETA-15660
BETA-75527
BETA-278334
BETA-203865,
BETA-127162,
UCIAMS-24865,
BETA-101935,
UCIAMS-24866,
OXA-1731
BETA-81355
W-3931,
AA-7160
DIC-1059
SI-4617
AA-114,
AA-115,
AA-117,
BETA-207579
BETA-81250,
BETA-88674,
BETA-81251
BETA-88673,
BETA-93001
BETA-79658
BETA-128231
GX-4569
BETA-71577
14
C YBP
t
Critical value
Cal BP
10375
10290
10410
110
460
60
0.002
3.84, 1
0.015
3.84, 1
12610e11850
13150e10670
12550e12030
10225
40
0.161
3.84, 1
12110e11750
10580b
40
19.7, 11
12690e12410
8290
10110
10260
9150
100
70
70
30
3.84, 1
9550e8990
12090e11290
12340e11700
10430e10190
10240
8570
9130
90
60
200
3.84, 1
12360e11600
9660e9460
10850e9690
10210
9940
10940b
60
50
20
15.197
11.1, 5
12150e11670
11640e11160
12840e12720
9530
10210
60
90
0.006
3.84, 1
11190e10590
12260e11540
8740
10610y
165
40
9.49, 4
10300e9380
12700e12500
8410
50
0.151
5.99, 2
11310e10110
8660
40
0.889
3.84, 1
9720e9520
9410
9890
9615
9850
190
40
225
160
14.86
0.00
3.305
15.95
9540e9300
11390e11190
11540e10340
11900e10780
Radiocarbon date is itself an average of multiple assays on the same specimen.
Dates are significantly different at 95% confidence interval; however, reporting authors suggest averaging is appropriate.
been performed to evaluate the accuracy of the newly obtained
date, we opted to include all of the dates in the pooled mean.
Second, a total of ten radiocarbon dates are reported for Shawneee
Minisink (McNett et al., 1977; Dent, 2002; Gingerich, 2007a, 2007b,
2011). McNett et al. (1985) reject two of these (W-3388
[9310 1000 14C YBP] and W-3391 [11,050 1000 14C YBP]),
presumably because of large errors. The remaining two dates from
McNett’s original work are statistically identical but have large errors compared to six recently obtained AMS dates on charred
Crataegus seeds (Dent, 2002; Gingerich, 2007a, 2011). These six
AMS dates are significantly different from one another at the 95%
confidence interval, yet all were obtained on charred seeds from
the same archaeological feature. In keeping with other treatments
of the site (e.g., Gingerich, 2007a, 2007b, 2011; Miller and
Gingerich, 2013), we opt to use the pooled mean of these six
dates as a single estimate of the age of ShawneeeMinisink.
Using the pooled mean procedure discussed above, our final
archaeological database contains 25 ages from 22 Paleoindian
archaeological sites. Two sites (Hidden Creek in Connecticut and
Varney Farm in Maine) have multiple statistically different age
ranges represented in their radiocarbon dates. There is as-yet no
way to identify which is the “correct” datedif not alldto associate
with human occupation at these sites, so we opt to include multiple
ranges for each site in our database. This procedure reduces the
M.T. Boulanger, R.L. Lyman / Quaternary Science Reviews 85 (2014) 35e46
chances of rejecting overkill because it increases the probability of
finding temporal overlap of extinct megafauna and human occupation of the Northeast because it potentially increases the time
depth of the latter.
4.2. Summed probability distributions
4.2.1. Constructing summed probability distribution curves
We follow methods outlined in recent studies that use radiocarbon dates as archaeological data (e.g., Hamilton and Buchanan,
2007; Shennan and Edinborough, 2007; Buchanan et al., 2008;
Tallavaara et al., 2010; Gajewski et al., 2011; Miller and
Gingerich, 2013). Individual radiocarbon dates and pooled means
were calibrated using the IntCal13 calibration curve (Reimer et al.,
2013), and summed probability distributions (SPDs) of calibrated
ages BP were created for each database using CalPal Advanced
(Weninger and Jöris, 2008). All ages mentioned below are given in
calibrated years BP and at the 2-sigma range unless otherwise
noted.
4.2.2. Interpretive and analytical challenges
Recently, the use of SPDs as population proxies, for humans or
other phenomena, has been the subject of some debate (e.g., Rick,
1987; Kuzmin and Keates, 2005; Surovell and Brantingham,
2007; Surovell et al., 2009a; Louderback et al., 2010; Steele,
2010; Buchanan et al., 2011; Williams, 2012). A thorough discussion of the pros and cons of these statistical constructs is best
left for another venue; however, some discussion of recent criticisms and how we address them is necessary here. Williams’
(2012) recent review highlights three methodological concerns
with the use of SPDs: (1) sample size, (2) effects of calibration
curve, and (3) taphonomic correction. Below, we address each of
these concerns as they impact our study. We find that Williams’
methodological concerns are peculiar to the temporal scale of his
own data (ca 40,000 years) and to his choice in calibration
software.
4.2.3. Sample size
ska and Pazdur (2004) demonstrate that the miniMichczyn
mum number of dates required to construct a reliable SPD is
dependent upon the mean standard error (DT) and the overall
span of time represented in a database. Williams (2012:587),
however, recommends that “at least 500 radiocarbon dates should
be used in any form of summed probability analysis” irrespective
of the duration of time involved in the analysis or of DT. Importantly, the radiocarbon database that Williams used spanned a
period of 40,000 years, and in this context a total sample size of
500 would equate to one date every 80 years or so. As applied to
the relatively brief span of time we address in the current study (ca
5000 years), a sample size of 500 dates would equate to a single
date every 10(!) years. We therefore feel, in agreement with
ska and Pazdur (2004), that effective sample size should
Michczyn
be dictated by the temporal scale of the study and the precision of
the available database.
In order to evaluate sample size requirements for our data, we
modeled a series of radiocarbon dates spaced at equal intervals
spanning a period of 8000 radiocarbon years (16,000e8000 14C
YBP), each with a standard error of 120 years, equal to DT of our
database. This span of time exceeds that in which we are interested
by several thousand years on either end, and thus should provide a
conservative estimate of sample size necessary for our study. The
results (Fig. 2) suggest that with a DT of 120, a sample of 33 or more
radiocarbon dates is sufficient to generate an SPD reflecting the
underlying distribution. Whereas our megafauna database is
almost twice this size, our Paleoindian database is slightly smaller.
41
4.2.4. Effects of calibration curve
Williams (2012) and others (e.g., Steele, 2010) have argued that
fluctuations in the calibration curve used by radiocarbon-datecalibration software directly influence the resultant shape of an
SPD. Both Williams and Steele used OxCal (Bronk Ramsey, 2009) to
generate their SPDs. Yet, whereas SPDs produced in OxCal are
strongly influenced by patterns in the underlying radiocarbone
calibration curve, there is no such sensitivity in CalPal (Buchanan
et al., 2011; Weninger et al., 2011; Schmidt et al., 2012) because
of the way in which Bayesian priors are applied to the posterior data
frequency. So, while we agree with Williams (2012) that the shape
of the underlying calibration curve will influence the shape of an
SPD in OxCal (and Calib), this is not a concern for our study, as we
make use of CalPal. Indeed, as shown in Fig. 2dthere is no
calibration-curve influence visible in the SPDs generated using a
uniform distribution of dates.
4.2.5. Taphonomic correction
As made clear by Lima-Ribeiro and Diniz-Filho (2013), the
youngest dated extinct animal and the oldest dated artifacts likely
do not represent the last living individual or the first colonizer,
respectively (see also Johnson et al., 2013 and references therein).
Older materials generally are less well and less often preserved
than younger materials (Surovell and Brantingham, 2007; Surovell
et al., 2009a). Thus, we acknowledge that the archaeological and
paleontological radiocarbon records are subject to some preservation bias and that these records are also subject to sampling bias.
For instance, remains of extinct megafauna found in what are
believed to be late Pleistocene sedimentsdand thus are suspected
of being contemporaneous with early Americansdare more likely
to be assayed by radiocarbon dating than are remains encountered
in contexts clearly pre-dating the human entrance into the Americas (Meltzer and Mead, 1983). Similarly, it may be that some time
periods (e.g., sites anticipated to be “the first” or “the earliest”) get
much dating attention (Grayson, 2011).
Surovell and Brantingham (2007; see also Surovell et al., 2009a)
suggest correcting any temporal frequency data by an empirically
derived factor to account for taphonomic bias (see also Johnson
et al., 2013). We agree this is good practicedparticularly when
comparing numbers of specimens over prolonged periods of time.
Yet, in this study, we compare the frequencies of two phenomena at
more or less the same point in time. Thus, correcting for taphonomic bias is largely irrelevant to our project. Indeed, applying the
correction advocated by Surovell et al. (2009a) has minimal effect
on the underlying frequency distribution of our data (Fig. 3). The
reason for this is simple: Surovell et al. (2009a,b) developed their
taphonomic-bias-correction factor to evaluate the relative frequencies of events occurring across spans of 15,000 and 40,000
years, whereas the temporal distributions of events we are
measuring are on a scale of a few thousand years and, significantly,
are of equivalent age. Certainly if wedlike Williams (2012)dwere
comparing the distribution of dates over a span of 40,000 years,
taphonomic bias would most definitely need to be accounted for. In
the case of our data, however, this does not appear to be an issue.
5. Results
The two resultant SPD curves are shown in Fig. 4. The SPD for
megafauna is bimodal, with one peak between 14,300 and
14,100 cal BP, and the other showing a relatively stable plateau
between 13,500 and 12,800 cal BP followed by a sharp spike and
drop at 12,800e12,700 cal BP. The sharp spike at 12,800e12,700 cal
BP is more-or-less contemporaneous with the first well-dated human occupation in the regiondShawneeeMinisink at (12,840e
12,720 cal BP; m ¼ 12,780 cal BP).
42
M.T. Boulanger, R.L. Lyman / Quaternary Science Reviews 85 (2014) 35e46
Fig. 2. Summed probability distribution curves generated with CalPal for six samples of equal-interval radiocarbon dates spanning the time period of interest. Note that below a
sample size of 33, the standard error between dates results in a curve characterized by peaks and valleys; whereas, with n ¼ 33 or greater, the curves reflect a continuous distribution that does not appear influenced by either sample size or by fluctuations in the calibration curve.
and the next-youngest date. Indeed, only 15 (26%) of our megafauna specimens produced dates younger than the initial date of
human occupation in the region. Of these 15 specimens, all but four
date to within one century of the date at ShawneeeMinisink. The
remaining four (7% of the total database) specimens (Mammut,
n ¼ 3; Castoroides, n ¼ 1) post-date the next-oldest-dated Paleoindian site (Vail, 12,700e12,500 cal BP; m ¼ 12,600 cal BP). Viewed
Megafauna
Actual
Modeled
Paleoindian
Actual
Modeled
0.0
0.2
0.4
p [rel]
0.6
0.8
1.0
The youngest megafauna specimen in our dataset, a specimen of
Castoroides from Wayne County, New York, dates to 12,070e
11,550 cal BP (m ¼ 11,810 cal BP). This alone would suggest that
there was temporal overlap of megafaunal and human populations
in the Northeast on the order of roughly 1000 years. However, as is
clear in Fig. 4, this youngest megafauna date appears somewhat
anomalous. That is, a period of roughly 500 years exists between it
18,000
16,000
14,000
12,000
10,000
14
C YBP
Fig. 3. Temporal frequency distributions of megafauna and Paleoindian radiocarbon dates in the Northeast between 18,000 and 9000
taphonomic bias following Surovell and Brantingham (2007) and Surovell et al. (2009a, b). Dotted lines represent actual data.
14
C YBP. Solid lines are data modeled for
M.T. Boulanger, R.L. Lyman / Quaternary Science Reviews 85 (2014) 35e46
43
Fig. 4. Summed probability distribution curves generated for megafauna specimens and Paleoindian archaeological sites in the American Northeast based on radiocarbon dates
available in 2013.
in another light, greater than 90% of known megafauna specimens
are as old or older than the first appearance of humans, and 75%
clearly pre-date human entrance into the region.
6. Discussion
The megafauna SPD is bimodal, with a clear increase in the
number of dated specimens leading up to ca 14,200 cal BPdover
1000 years before any evidence of human presence in the region.
The initial decline in large herbivore populations ca 14,100 cal BP is
unrelated to human presence in the region. The temporal span of
this earlier event is consistent with a collapse of Northeast megafaunal populations hypothesized to have occurred between 14,800
and 13,700 cal BP based on Sporormiella spore abundance (Gill
et al., 2009; Robinson and Burney, 2008; Robinson et al., 2005;
but see; Feranec et al., 2011; Parker and Williams, 2012; Raper and
Bush, 2009). Though Robinson et al. (2005) suggested some degree
of human involvement with this decline, our data clearly suggest
that humans were not a factor during this time period. A collapse of
megafauna populations at this time is also suggested by an
apparent genetic bottleneck of various mammalian taxa during the
terminal Pleistocene (references in de Bruyn et al., 2011), though
we concede that the chronological resolution of this genetic evidence is not as precise as that offered by radiocarbon-dated remains and soil cores. We also note that the timeframe of this
increased number of dated megafauna specimens is coincident
with the onset of extreme aridity at 14,500 cal BP across large
portions of North America (Polyak et al., 2012).
The second peak of megafauna radiocarbon dates falls between
13,600 cal BP and ca 12,700 cal BP. Yansa and Adams (2012)
document significant dietary stress in proboscidean populations
of the neighboring Great Lakes region 13,500 and 13,000 cal
BPdwell in line with the second peak in our megafauna SPD, and
coincident with regionally documented increases in temperature,
lake level, and vegetation change (Munoz et al., 2010). Because this
increase in megafauna dates precedes the appearance of humans,
and yet is commensurate with documented environmental change
and documented dietary stress in megafauna of neighboring areas,
we interpret the second peak to most likely be the result of a
combination of dietary-stress induced deaths. We do, however,
concede that there may be some sample bias evident, reflecting a
higher probability of dating what seem to be terminal Pleistocene
megafauna. The drop in the megafauna SPD ca 12,700 cal BP is
preceded by the single archaeological date at ShawneeeMinisink of
12,780 cal BP noted above. The two SPDs thus suggest human
arrival at the tail end of a prolonged extinction process that had
been occurring for more than 1000 years beforehand (since ca
14,100 cal BP).
One could argue the temporal overlap presented by the two SPD
curves supports an overkill scenario. This ignores the fact that (A)
overkilldincluding the Blitzkrieg modeldby definition, was the
singular cause of the terminal Pleistocene extinction of megafauna,
and yet the SPDs suggest increases in the deaths of megafauna well
before humans arrived; and, (B) not one specimen in our megafauna database shows evidence of human involvement in its death,
and not one of the archaeological sites in our database contains
evidence of the hunting of megafauna.
If our results are interpreted as supporting overkill of any sort,
we are left having to explain how human hunting resulted in pronounced decline in megafauna for over 1000 years (from 14,100 cal
BP to 12,780 cal BP) while leaving no evidence of human occupation, bone modification, or butchering on the hundreds of megafauna specimens that have been recovered. We are also left trying
to explain why humans began leaving archaeological traces in the
region later than the mean radiocarbon dates of more than 90% of
all known megafaunal remains, and why no known archaeological
site in the region contains evidence (equivocal or otherwise) of
megafauna hunting.
In short, we believe that the simplest explanation, that which is
most in line with all available evidence, and that which requires the
fewest assumptions, is that megafaunal extinction processes in the
American Northeast began well before humans arrived in the region. During the Pleistocene to Holocene transition the taxonomic
composition of mammal communities shifted from so-called “no
analog” faunas to faunas of modern composition (Faunmap
Working Group, 1996). Mean body size of bison (Bison spp.), bighorn sheep (Ovis canadensis), wapiti (Cervus canadensis), wood rats
(Neotoma spp.), horses (Equus sp.) and other taxa in North America
decreased during the late Pleistocene (Hill et al., 2008; Lyman,
2009, 2010; Lyman and O’Brien, 2005; Guthrie, 2003, respectively). The diminution process seems to have preceded the first
appearance of humans, implicating an environmental cause of a
stressful time for at least some mammals. Given the absence of
evidence for direct association of humans with Pleistocene megafauna, an environmentally dynamic terminal Pleistocene, and what
seems to be a depleted population of megafauna, we, like Haynes
(2013), suspect the SPDs indicate human entrance into the Northeast at a time when megafauna were depleted in abundance and
thus found in geographically (and hence genetically) isolated
populations. If this suspicion is correct, then if human hunters had
any input into extinction of Pleistocene megafauna in the Northeast, it was only the coup de grace in a process largely driven by
nonhuman mechanisms.
7. Conclusions
The SPD of Paleoindian archaeological components displays
minimal overlap with the tail end of the SPD for directly dated
megafauna specimens. This minimal overlap suggests that the two
were contemporary for only a brief span of time. The SPDs also
indicate declines in megafauna populations preceded human
entrance into the American Northeast. These findings are independent of, and supportive of, conclusions based on Sporormiella
abundances and genetic evidence suggesting declines in
44
M.T. Boulanger, R.L. Lyman / Quaternary Science Reviews 85 (2014) 35e46
megafauna populations prior to the arrival of humans, as well as
with paleoclimatic data indicating periods of environmental
change. This scenario, if correct, explains why archaeologists and
paleontologists have as yet failed to identify any unequivocal associations of humans and megafauna in the Northeast. If people
had a hand in the extirpation, it seems to have been at best a coup
de grace. Whatever drove local declines in regional megafauna
populations, chronological evidence suggests that humans had a
minimal role. We stress that our data do not speak to continentwide population dynamics of megafauna, or to extinction processes elsewhere in North America. That is, the declines we see in
Northeast megafauna populations may be a cascade effect from
declines in regional populations elsewhere on the continent that
may or may not have been the result of human hunting. Yet, in the
Northeast itself, the presently available data do not support a scenario in which humans hunted megafauna to extinction in the
fashion suggested by Martin’s original or Blitzkrieg overkill
hypothesis.
Acknowledgments
We thank Michael J. O’Brien, Briggs Buchanan, Donald Grayson,
and numerous anonymous reviewers for insisting on brevity, clarity
and focus. We thank Gregory Lattanzi, David Parris, R. Michael
Stewart, and Guy Robinson for sharing radiocarbon dates for this
study. Some data used in this study were obtained from the Neotoma Paleoecology Database (http://www.neotomadb.org), and the
work of the data contributors and the Neotoma community is
gratefully acknowledged.
Appendix A. Supplementary data
Supplementary data related to this article can be found at http://
dx.doi.org/10.1016/j.quascirev.2013.11.024.
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