The First Human Settlers on the Yucatan Peninsula: Evidence from Drowned Caves in the State of...

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Chapter 19

The First Human Settlers on the Yucatan Peninsula: Evidence from

Drowned Caves in the State of Quintana Roo (South Mexico)

Arturo H. González1, Alejandro Terrazas2, Wolfgang Stinnesbeck3, Martha E. Benavente2, Jerónimo Avilés4, Carmen Rojas5, José Manuel Padilla1,

Adriana Velásquez5, Eugenio Acevez4, and Eberhard Frey6

ABSTRACTPrehistoric evidence from submerged caves and sinkholes (cenotes) on the Yucatan peninsula provides strong evidence for the existence of an early preceramic human settlement in southern Mexico. During our ongoing paleoanthropological research we have already documented three well-preserved human skeletons as old as 13,000 and 9000 years from these sites in Quintana Roo (Gonzalez et al. 2008a, Gonzalez et al. 2008b). The findings were associated with hearths and a diverse megafaunal assemblage of late-Pleistocene age. A fourth human skeleton was discovered in 2009, two more in 2010, and two others in 2011. Here we provide a first register of these additional five skeletons, bringing the total assemblage to eight. A ninth skeleton was informally reported from the same area by INAH researchers. These findings thus constitute one of the largest databases on bones of early humans in Mexico.

KEYWORDS: Cenotes, Mexico, Quintana Roo, Karst, Human settlement, Paleoamericans, Pleistocene, Holocene, Underwater archaeology

quickly disappears into the limestone of a kilometers-thick car-bonate platform and runs subsurface to the sea. The ground is pierced by vine-draped sinkholes—cenotes, as they are called lo-cally—where the roofs of underground caverns have collapsed (Lopez Ramos 1975; Smart et al. 2006; Ward et al. 1985). Phre-atic levels are reached only a few meters below surface. From here the discharge of ground water is rapid and directed towards the coast. The enormous degree of karstification and limestone permeability in the subsurface of the northern Yucatan led to the formation of one of the most extensive active cave systems worldwide, with an explored length of approximately 700 km and a presumed extension of 7,000 km (Quintana Roo Speleologi-cal Survey (QRSS), www.caves.org/project/qrss).

1 Museo del Desierto, Saltillo, Mexico 2 Área de Prehistoria y Evolución del Instituto de Investigacio-

nes Antropológicas de la Universidad Nacional Autónoma de México (UNAM)

3 Institute of Earth Sciences, University of Heidelberg, Germany 4 Instituto de la Prehistoria de America, Playa del Carmen,

Mexico 5 Instituto Nacional de Antropología y Historia, Tulum, Mexico 6 Staatliches Museum für Naturkunde, Karlsruhe, Germany Corresponding author e-mail: [email protected]

IntroductionThe northern part of the Yucatan Peninsula in Southeast Mexico is a flat landscape where no surface rivers flow because the rain

The First Human Settlers on the Yucatan Peninsula: Evidence from Drowned Caves

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This enormous subterraneous karst labyrinth was formed during the last two to three million years, mostly during the Pleistocene (Ward et al. 1985). During the glacial stages of this geological period, precipitation in the northern Yucatan peninsula was likely higher and sea level 100 m and more be-low the level of today (Blanchon and Shaw 1995; Moseley et al. 2013). Sea-level rise at the end of the Pleistocene and early Holocene was caused by the global deglaciation, between 13,000 and 7,600 before present. This eustatic rise of the sea level was considered “catastrophic” by Blanchon and Shaw (1995). The present-day sea-level was reached about 6600 cal yr BP (Gabriel et al. 2009). Without the sinkholes and caves with groundwater, much of northern Yucatan would be a waterless plain and one of the most inhospitable regions in the world because of paucity of fertile soil, the scarcity of drinking water, and shortage of other natural resources (Ward et al. 1985). Nevertheless, one of the most sophisticated pre- Columbian civilizations, the Maya, did indeed cope with these adverse environmental conditions. Recent archaeological discoveries in the Mexican state of Quintana Roo suggest, however, that the arrival of humans to this region was much earlier and dates back to the end of the Pleistocene, thousands of years prior to the classic Mayan civilization. (Gonzalez et al. 2008a, Gonzalez et al. 2008b). In 2008 we documented paleontological and anthropo-logical evidence from about a dozen sites in the Tulum area of Quintana Roo. The fossil assemblage is of late-Pleistocene to early-Holocene age (Gonzalez et al. 2008a, Gonzalez et al. 2008b). The association includes horses, foxes, agoutis, peccaries, bats, elephants, tapirs, llamas, ground sloths, and glyptodonts. Some of these animals are widely known from North America as characteristic of shrub-type vegetation. At or near the Pleistocene/Holocene boundary, however, the dominant vegetation of thorny shrubs disappeared and tropi-cal forests arose. They quickly became dominant at approx. 9000 years BP (Leyden 1995; Brenner et al. 2002; Leyden et al. 1993). Among the most important discoveries (reported by Gonzalez et al. 2008a, Gonzalez et al. 2008b) were three hu-man skeletons called Naharon, Las Palmas, and El Templo, which are almost complete (> 80%) and anatomically articu-lated (Tables 19.1, 19.2). They were recovered from depths

of 23 m, 24 m, and 9 m, respectively, in the submerged cave systems, which must have been flooded during early stages of the Holocene sea-level rise. The taphonomic circumstances suggest that at least two skeletons, Las Palmas and Naharon, were intentionally deposited. The position of El Templo individual suggests an accidental death. We assume that these skeletons are of latest-Pleistocene/early-Holocene age based on radio-metric dating (Tables 19.1, 19.2). The Naharon individual, also known as “Naharon Woman,” was discovered by G. Walten and J. Coke and subsequently reported to one of us (JA). Her age at death was estimated at 20–30 years. Her death was dated on bone collagen to 11,570 ± 65 14C yr BP (UCR4000A), using mass spectrometer acceleration techniques (MSA) (Gonzalez et al. 2008a, Gonzalez et al. 2008b). Nevertheless, these ages must be considered with caution, because the amount of organic matter detected in the bones is extremely low (Taylor 2009). The Las Pal-mas individual (Tables 19.1, 19.2), also known as “Mujer de las Palmas,” a female discovered by J. Coke and reported to one of us (JA), reached an age of 44–50 years and was dated to 8050 ± 130 14C yr BP (UGA-6828) using 14C, and to 12,000–10,000 BP using U/Th techniques (Gonzalez et al. 2008a, Gonzalez et al. 2008b). The El Templo individual (Tables 19.1, 19.2) was a male 25–30 years old at the time of death. It was discovered by S. Gerrard, G. Klag and D. Martin, and reported to one of us (JA). Bone tissue was too much degraded and collagen contents too low to get reliable radiometric 14C ages. Criteria for identifying sex and age of the El Templo male were already reported by Gonzalez et al. (2008a). The discovery of human skeletons associated with hearths and a diverse faunal assemblage of latest-Pleistocene age clearly indicates an early human settlement on the Yu-catan peninsula reaching back to the late Pleistocene or early Holocene. Here we present new anthropological evidence from our ongoing research and report on five additional human skele-tons from the cave systems of Quintana Roo state. These skel-etons, here referred to as Chanhol I, Chanhol II, Muknal, Pit I, and Pit II (compare Tables 19.1 and 19.2) were discovered since 2008. A ninth individual was recently reported from the same area at Cenote Black Hole by Instituto Nacional de

Table 19.1 Complete list of human skeletons.

Site Cave system Cave subsystem Cenote entrance Distance from entrance (m) Depth (m) Discoverer

Naharon Ox Bel Ha Naranjal Naharon 368 23 G. Walten and J. Coke

Las Palmas Ox Bel Ha Muknal Palmas 174 24 J. Coke

El Templo Templo ElTemplo 185 10 S. Gerrard, G. Klag, and D. Martin

Chan Hol I Toh Ha - Chan Hol 547 8 A. Kampe and T. Kampe

Chan Hol II Toh Ha - Chan Hol 1240 8 H. Gust

Muknal Ox Bel Ha Muknal Palmas 210 33 J. Aviles

El Pit I Sac Actun Dos Ojos Pat Jacinto 47 30 Unknown

El Pit II Sac Actun Dos Ojos Pat Jacinto 12 45 Unknown

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Antropología e Historia (INAH) researchers. The assemblage now represents the largest database on bones of early hu-mans in Mexico. Table 19.1 shows the complete list of human skeletons.

New Discoveries about Early Human Settlement in YucatanFigure 19.1 shows the coast of the Mexican state of Quintana Roo with the location of cenotes and caves containing sites with human skeletons and associated Pleistocene to early-Holocene fauna. The area of study stretches from Tulum to-ward Playa del Carmen. All sites are between a few hundred meters to a maximum of 10 km from the actual coastline. Black dots mark sites that contain human evidence; white dots represent sites that contain animal evidence; black-and-white dots indicate sites that contain both human and animal evidence.

Here we document several new locations in the Tulum area. At Chan Hol cave, two human skeletons were recently discovered, but one of them (Chan Hol II) was subsequently stolen from the submerged cave and only about 10% of this skeleton could be recovered. Two skeletons discovered at Pat Jacinto (formerly known as “El Pit”) as well as one at Muknal cave were saved from potential vandalism. Both localities are visited by an increasing number of recreational cenote and cave divers via newly constructed roads to these cenotes.

Chan HolThe Chan Hol cave, which forms part of the Toh ha system, was first explored by Kim Davidson in 2005. The known ex-tension of the cave system is estimated today at more than 5000 m. The main entrance, known as Chan Hol cenote, is located approximately 15 km south of Tulum close to high-way 307, which connects Tulum with Playa del Carmen. The

Figure 19.1 Coast of the Mexican state of Quintana Roo with location of cenotes and caves containing sites with preceramic human skeletons and associated Pleistocene fauna. The area of study stretches from Tulum toward Playa del Carmen. All sites lie between a few hundred meters to a maximum of 10 km from the actual coastline.

Table 19.2 Homogenized radiometric ages of human remains discovered in submerged caves of Quintana Roo, Mexico. Calibrated in Oscal 4.2 using the Inical 09 data set.

Site Sample number Laboratory Technique Radiocarbon or U/Th age Calibrated age (cal yr BP)

Naharon UCR4000A U. C. Riverside 14C AMS collagen 11,570 ± 65 11,771–11,404 (95.4%)

Las Palmas UGA-6828 U of Georgia 14C AMS collagen 8050 ±130 7356–6641 (94.8%) Las Palmas Oxford U/Th 10,000–12,000

El Templo - - - - -

Chan Hol I KIA-43520 Kiel 14C in apatite 9589 ±49 9194–8792 (95.4%)

Chan Hol II - - - - -

Muknal UNAM-1240 UNAM 14C in charcoal 8890 ±100 9732–10,298 (98%)

El Pit I KIA-43524 Kiel 14C in apatite 11,332 ±64 11,396–11,150 (95.4%)

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entrance is semilunar in shape, 3–4 m wide, and partially covered by a natural roof of limestone. Water level at this entrance is shallow, only about 0.5–0.8 m deep, but deepens gradually to a cave 8–10 m deep. Two human skeletons dis-covered in the Chan Hol cave were named by us Chan Hol I, also known as “El Joven” (Figure 19.2) and Chan Hol II, also known as “La Niña” (Figure 19.3).

Chan Hol I The Chan Hol I skeleton was discovered in 2006 by cave ex-plorers Alexandra and Thorsten Kampe and reported to us by Robbie Schmittner. It is located approximately 530 m north-east from the entrance. Depth at the site is 8 m. The skel-eton was found partially articulated and in a lateral position, resting on its left side, with legs flexed to the body at an angle of about 90 degrees. The right arm was stretched out. A stalactite, about 1.2 m in length, had collapsed on the arm

and may have caused the fracture of the diaphysis of the right humerus in its distal third (Figure 19.4). Unrelenting contact with slowly flowing fresh water resulted in poor preservation of the skeleton. Bones are exceedingly fractured and fragmented and spongy bone is mostly dissolved. Despite the poor preservation, ana-tomical relationships are clearly recognized and indicate that an overall original anatomical position is preserved, including even tiny segments of extremities such as pha-langes (Figure 19.5). The Chan Hol I skeleton is about 90% complete, but only 60% of the bones were sufficiently well preserved to be col-lected, owing to dissolution of the bone substance. The flexed position of both legs, and the fact that even the smallest bones of hands and feet maintain their anatomical position, clearly indicate that skeletonization occurred on site, at a time when the cave was still dry and not yet filled with water.

Figure 19.2 The Chan Hol I skeleton.

Figure 19.3 Chan Hol II individual before looting of the skull and other bones. Photo courtesy of Liquid Jungle.

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The strong dissolution observed in most diagnostic ele-ments of the Chan Hol I skeleton prevents our determining reliable data regarding the sex or age at the time of death of this individual.

Chan Hol II The Chan Hol II skeleton is located in a small cave tunnel ap-proximately 1,200 m west of the Chan Hol cenote, at a water depth of only 8 m and thus at a similar depth as the Chan Hol I individual. The tunnel is reached via the same cenote entrance. The skeleton was discovered in early 2009 by Harry Gust and reported to one of us (JA). Subsequently the site was vandal-

ized by an unknown cave diver during the summer of 2012. At present, only a few photographs exist from the site prior to vandalization (Figures 19.6, 19.7). These photos indicate that the Chan Hol II individual was likely > 80% complete, including the skull, and that decay and skeletonization occurred in situ. After the looting of the Chan Hol II site and robbery of the skull and numerous large bone elements, we returned to the location in October 2012 to collect all bone fragments, which remained dispersed on the cave ground or were ad-hering to an aragonite layer covering the cave bedrock lime-stone. Even though the majority of these bone fragments were small, less than 50 mm in size, they represent approxi-

Figure 19.4 Chan Hol I skeleton. The figure shows a detail of Figure 25.2. A stalactite fell from the cave roof and fractured the humerus.

Figure 25.5 Left foot of the Chan Hol I skeleton. Note that bones (e.g., talus, cuboid, metatarsals, and phalanges) maintain their original position, indicating an in situ skeletonization in a dry cave.

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mately 10% of the skeleton. We collected 51 fragments which correspond to ribs, 6 vertebrae, fragments of feet and hands, one patella, 6 fragments of tibiae, 2 of the left humerus, 3 of the left radius, one of the clavicle, 4 teeth, various fragments of the pelvis, 3 of the scapula, as well as single fragments of the temporal and occipital condyle. The arms and legs of the skeleton were articulated and preserved in an anatomical position. In addition, a large sta-lagmite grew on the pelvis of the skeleton. Incisive teeth recovered from both the Chan Hol I and Chan Hol II individuals present a “sinodont,” shovel-shaped, morphol-ogy, and thus provide an important source regarding the biologi-cal affiliation of these early settlers and their origin in relation to the populations in East and North Asia (cf. Turner 1990).

Ox Bel Ha SystemOx Bel Ha is located in the Tulum area. This huge system ex-tends from the jungle and mangroves south of Tulum to

the Caribbean Ocean. With 243.031 km of explored caves and tunnels, it has absorbed all neighboring systems. At least 140 different cenotes lead to this huge system, many of them very popular among cave divers. Maximum depth recorded in the system is 34.7 m at the Muknal archaeo-logical site, from which a human skeleton is reported here. The ongoing exploration and mapping of caves in the Tulum area has shown that the Ox Bel Ha system is connected to other systems in the area, including the Naranjal and other systems as well as the Muknal cave. In these cases the larger system (Ox Bel Ha) swallows up the smaller ones and only the name of the larger system is retained. Following this nomenclature, the Nara-njal system has recently been absorbed by the Ox Bel Ha system. For a better understanding of terms already introduced to the anthropological literature (e.g. Gonzalez et al. 2008a, Gonzalez et al. 2008b), we here maintain the term Naranjal sub-system, as well as Naharon and Muknal remote siphon areas which are part of the Naranjal system (“QRSS” 1989–2001).

Figure 19.6 Chan Hol II individual before looting of the skull and other bones. Note that a stalagmite grew on the pelvis of this skeleton, thus indicating that the cave floor was dry during and after skeletonization of the corpse. Photo courtesy of Thomas Spanmberg.

Figure 19.7 Chan Hol II site after looting of the cranium and the major portion of bones of this skeleton. Only small fragments remained on the cave floor.

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Naranjal Prior to the discovery of its connection with the Ox Bel Ha cave system, the Naranjal system had a mapped length of 24.5 km, with 8 known entrances (Figure 19.8). Two preceramic human skeletons, Naharon and Palmas, have already been documented from Naranjal system by Gon-zalez et al. (2008a, Gonzalez et al. 2008 b; Tables 19.1 and 19.2). The Naharon Woman was 20–30 years old at death. The skeleton was discovered in an articulated condition, in-dicating decay occurred in situ (Gonzalez et al. 2008a, Gonza-lez et al. 2008b). The “Señora de Las Palmas” was discovered about 1 km distant from the Naharon individual in an area of the same cave system known as Muknal remote siphon, at a depth of 24 m and a distance of 174 m from the near-est entrance. This individual had reached an age of 44–50 years. The skeleton was articulated, with the legs flexed to the body, suggesting an intentional deposition, likely a funer-al. Figures 19.9, 19.9A, and 19.9B show the reconstruction of the Las Palmas female, completed in 2010 at the Atelier Daynes Studios at Paris, France, by Elisabeth Daynes. Subsequent to the findings of the Naharon and Las Pal-mas individuals, further reconnaissance and exploration of the Naranjal system led to the discovery by one of us (JA) of a new skeleton only 60 m from the Las Palmas site at a depth of 33 m. Here we refer to this new skeleton as the Muknal individual.

Muknal IndividualThe Muknal skeleton was found at a location elevated about 0.5 m above the cave floor within and partially overlying an ex-

tensive accumulation of charcoal (Figure 19.10). The charcoal layer is 0.1–0.5 m thick and spreads over an area 30 m long and 2 m wide. A charcoal sample taken from below the Muknal skeleton was dated to 8890 ± 100 14C yr BP (UNAM-1240) at the UNAM laboratory (Instituto de Investigaciones Antrop-ológicas) using C-14 Liquid Flash Spectrometry techniques. Some of the superficial bone tissue of the Muknal in-dividual has been lost from chemical dissolution as well as abrasion, even though there is no evidence of water-borne transport. For instance, no traces of erosion or rounded mar-gins are recognized on bone surfaces or fracture margins. Bone is pale yellow in color, but black patches are present, likely resulting from contact with the charcoal concentrated on the cave ground. The Muknal skeleton is approximately 50% complete, in-cluding skull, mandible, cervical bones, and some long bones. The skeleton was not found articulated; instead, bones were distributed randomly (Figure 19.11). It is unclear whether they were transported to the site by water run-off, which ap-pears unlikely from its location in an elevated location on the Muknal cave floor adjacent to the charcoal accumulation as well as the absence of transport marks on the bones. Alterna-tively, prehistoric settlers may have deposited some skeletal parts at the Muknal site. This latter interpretation appears to be more likely based on the evidence.

Osteology of the Muknal individualSkull As a result of post-mortem fractures and superficial dis-solution of the ethmoid and the internal portion of the orbits, only the wings and spines of the sphenoid are preserved.

Figure 19.8 Map of the Naranjal cave and cenote system adjacent to Tulum, Quintana Roo, with location of anthropological sites described here. Modified from QRSS (2007). Note that three human skeletons were recovered from this subterraneous system so far.

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A post-mortem fracture is identified in the infe-rior portion of the malar. The zygomatic arches are fractured; margins are clearly recognized, suggest-ing that the fracture is recent. In the maxillae, the entire portion adjacent to the sphenoid is lost, in-cluding the posterior alveolar region from the first molar in the right side and all teeth from the third molar on the left side. The upper anterior portion of the right maxilla is also missing, as well as the plate of the ethmoid, the infraorbital margin, and inferior margin of the maxilar. Almost the entire base of the cranium is lost, with only the posterior margin of the foramen magnum preserved. Fractures on the cranial base preserve black rims indicating that they

Figures 19.9, 19.9A, 19.9B Reconstruction of the Las Palmas female, performed in 2010 at the Atelier Daynes at Paris, France, by Elisabeth Daynes. Photo courtesy Elisabeth Daynes.

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are considerably older than fractures, which affected the facial region. Most teeth were lost ante mortem, among them the right lateral incisive, the second right premolar, the left ca-nine, and the first left premolar and first left molar. A possible left premolar of the upper jaw and badly preserved roots of other unidentified teeth are preserved. Skullcap and the right orbit are unfractured, but part of the left malar and the central portion of the maxillar were integrated into their original anatomical position in the lab.

Sex of the Muknal individualTo determine sex in a fossil human cranium, the following characters need to be considered:

1) morphology of mastoid apophyses,

2) occipital condyles,

3) muscular incertation of the occipital

4) frontal protuberances,

5) the width of the zygomatic arcs,

6) the supraorbital margin,

7) orbital delimitations,

8) the form of palatinal bones, and

9) the mandible architecture (Brothwell 1987 in White and Folkens 2000).

The interpretation of sex follows the propositions of Buiskra and Ubelaker (1994): Superciliar arches are medially marked. They fuse with the glabella to form a robust bulge, as-sociated to grade 4 in the scale of Buiskra and Ubelaker (1994). The nucal crest is little accentuated, reaching grade 3 in this scale, whereas the mastoid process is medium-sized, anteriorly inclined, in the range of grade 3. The supraorbital margin is fine, slightly rounded, and elevated grade 4 in this scale (op.

cit.). Chin morphology is modified due to alveolar absorption caused by the loss of teeth; a marked triangular chin is present and in the range of grade 3 to grade 4. These criteria indicate that the Muknal skeleton represents a male individual.

AgeThe following criteria were used to estimate the age of the Muknal individual: Despite the fact that the individual lost all molars during life, the eruption of the third inferior and supe-rior molars was completed. The few teeth that are preserved in the mandible show extreme abrasion, reaching grade I of dental attrition in the scale of Lovejoy (1985 in White and Folkens 2000), whereas the maxillary teeth abrasion reaches grade H. This suggests that the age of the individual may range between 45 to 55 years, considering the mandible, and between 40 and 50, based on the maxilla. Cranial sutures were analyzed following the methodology established by Lovejoy and Mendl (1984 in White and Folkens 2000), suggesting an age of 48.5 (SD 10.5) for the first sutures group, and 56 (SD 8.5) for the second. However, these standard techniques are known to present a wide range of error and the Muknal individual shows little bone-tissue degeneration. The age at death may therefore be lower than proposed above and may actually range between 40 and 45 years.

PathologiesThe Muknal individual shows evidence for pathological pro-cesses, principally based on dentition. The ante-mortem loss, in the maxilla, of the two central incisors, the left lateral inci-sor, the second left premolar, the left molar, and all three right molars is indicated by alveolar reabsorption. The remaining first right premolar and second left molar show evidence of alveolar retraction and severe periodontal abrasion reaching the pulp chambers, as well as occlusal caries in the distal por-tion of the right premolar. Dental calculus is absent. In the

Figure 19.10 The Muknal individual. This skeleton was found in the deepest part of the Muknal cave, at a depth of 33 m, on a slightly elevated shelf about 0.5 m above the cave floor within and partially overlying an extensive accumulation of charcoal.

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mandible all left molars, the second left premolar, left canine, all incisives, both right premolars, and the second and third right molars were lost during the life of the individual. The remaining first left premolar and first right molar are worn down and show occlusal caries in the right molar, extending into the pulp chamber. The temporomandibular joints present arthrosis with bone tissue reaction, principally on the left side. There is a slight supra-inion injury on the left side with reaction on the occipital. The right orbital roof presents a marked criba orbitalia, including remodeling of the bone tissue. A healed porotic hyperostosis is registered in the bregma region, while another reaction of the bone tissue was detected on the su-perior margins of both auditive conducts, but primarily on the left side.

Comments on the osteologyThe cranium of the Muknal individual is ovoid in shape and thus corresponds to a mesocranial (for a definition of the craniometric indexes see Comas, 1966) morphology (78.48), with a narrow nose (leptorrin, 40.81) and low orbits (cam-econc, 82.92). In general terms, the cranium is bigger than those of Naharon and Las Palmas, but within the range of the El Templo individual that was attributed to a male. On the other hand, the facial region, i.e., the narrow nose, resem-bles the Naharon female, whereas the Las Palmas female has a wider nose. The low orbits are a common feature in all the submerged cave individuals where this character is preserved in Muknal, Las Palmas and possibly Naharon.

Sac Actun systemIn 2012, the 82.291-km-long Dos Ojos system was reported by Peter Sprouse as forming part of the Sac Actun great sys-tem, known to be 222.673 km long. The two systems are con-nected by swamps, dry land, and partially water filled caves.

However, Sac Aktun and Dos Ojos are flooded caves, sepa-rated, but technically “connected,” by partially water filled caves. The total length of both caves (wet and dry) reaches 308.487 km (QRSS 2013:http://www.caves.org/project/qrss/qrdry.htm). With a maximum depth of 130 m, Dos Ojos is one of the deepest cave systems on the Yucatan peninsula and the deepest known in Quintana Roo; it is therefore popular for deep diving. Here we report on two partially preserved hu-man skeletons from the Pat Jacinto cenote, also known as El Pit (Figure 19.12). The cenote was first explored in 1994 by Kay Walten and Dan Lins. This cenote is located 4 km south of the Xel Ha inlet. It is reached from highway 307 via a dirt road at Dos Ojos Cenotes Park entrance that connects Cancun and Tulum.

Cenote Pat Jacinto (Previously Known as El Pit)The dispersed bones of at least two human individuals were discovered by unknown cave divers in the Pat Jacinto cenote and reported to us by cave-diving instructor Luis Leal. Both remains form part of the debris mound of the cenote and were found in water depths of 30 to > 45 m. Bones as well as the taphonomic context have been de-graded by sulfuric acid in the water of Pat Jacinto cave, which forms clouds at depths below approximately 35 m. Dissolu-tion is strongest in the deep parts of the cenote, where cave sediment is in contact with water. Bone color is brown-yellow on the coronal part, which was covered by sediment, and lightly colored in parts exposed to the cave water.

El Pit IThe El Pit I individual consists of a fragmentary cranium dis-covered at a depth of 30 m. Postcranial material, which likely belongs to the same individual, is also included in the present preliminary description (Figure 19.13).

Figure 19.11 Muknal skeleton. Basal view of the cranium.

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SexThe nucal crest is well developed, reaching grade 4 on the scale developed by Buikstra and Ubelaker (1994). Even though no other diagnostic elements are preserved, this character suggests that the Pit I individual is a male.

AgeIn the absence of other characters, the low degree of fusion of the cranial sutures suggests that the Pit I human was a young adult. The mandible, which likely belonged to the same individual, shows the complete eruption of the third molar, even though dental abrasion is not very pronounced. This reinforces the idea that the Pit I skeleton belonged to a young adult.

PathologyWe determined a small traumatic lesion recovered in life in the frontal bone immediately above the left superciliary arch and a slight exostosis affecting the upper margin of the right auditory canal.

ConservationThe encephalic portion of the cranium is preserved, but the total facial region and base are lost. The squama frontalis is preserved above the glabella, but this is not enough to mea-sure the maximum length of the cranium. The sphenoid is majorly lost, but small fractions adhering to the temporal are preserved and indicate that the sphenotemporal sutures were not fused yet. The temporal preserves mandibular pits, the

auditive conducts, and the mastoid region up to the mastoid holes. The mastoid apophyses are fractured. The occipital is broken in a paracoronal direction and at the height of the in-sertion of the Rect. Cap. Post Major and Minor, thus preserving the external protuberance and a portion of the occipital crest.

CommentariesThe Pit I cranium was discovered close to the entrance of the Pat Jacinto cave and forms part of the debris mound of the cenote. In addition to the radiometric dating (see Table 19.2) of some of the human bones from this cenote, the cra-nial morphology, even though incomplete, suggests that the Pit I skull differs from that of Mayan settlers by the absence of intentional cephalic deformation, a common character seen in about 80% of pre-Hispanic crania (Tiesler 2012), and by its overall mesocranial shape, even though this interpre-tation needs to be substantiated by more detailed research.

El Pit IIThe El Pit II individual is composed of a parietal partially artic-ulated with the occipital, as well as on postcranial parts that were discovered covering the debris mound of the El Jacinto cenote in water 44–45 m deep. These remains are presently under study, and only a preliminary description is given here.

OsteologyA fragment of the left parietal preserves an almost complete occipital margin. In the lower edge the posterior region of the squamous border is preserved although the medium por-

Figure 19.12 3-D sketch of the cenote Pat Jacinto, formerly known as El Pit. Note that the remains of two individuals when discovered formed part of the debris mound of the cenote in water depths of 30 to >45 m.

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tion is missing, including the articulation with the sphenoids. Anteriorly, the coronal suture and the anterior half of the sag-ittal suture are lost, even though the latter is well conserved in its posterior half. The external diploe is little eroded, but its inner portion is majorly dissolved, as is the major part of the trabecular tissue. The second fragment corresponds to the occipital and conserves the left lambdoid suture, from Lambda to the lateral angle and the superior part of the mastoid portion. From here, a fracture connects with the inferior curved line, raising the medial portion and running vertically to Lambda. Consequently, the entire lower right portion of the occipital is missing, including the region around foramen magnum. The left parietal and the occipital articulate along the lambdoid suture, even though alignment is imprecise owing to marginal dissolution in both bones. The sex of the individual is yet undetermined, but some characteristics suggest its age at the moment of death: Cranial sutures are widely open and preserve sharp margins, without

increasing and presently comprises eight individuals. Bone material is majorly affected by post-depositional dissolution processes, which modified the compact surface and spongy bone and nearly completely degraded collagen, especially in shallow cave settings where the bone is exposed to fresh wa-ter. This dissolution debilitates the cohesion of organic and inorganic portions of the bone and makes it vulnerable to fragmenting. It also hampers the use of radiometric C-14 dat-ing methods because of widespread dissolution of a measur-able organic component (Taylor 2009) (Table 19.2). Even in cases when radiometric data are absent, or sus-pect owing to insufficient collagen, the cranial morphology of the cenote individuals is observably considerably different from pre- and post-Hispanic Maya. In addition, intentional cephalic deformation seen in the majority of Mesoamerican pre-Hispanic crania is absent (Tiesler 2012). In a few cases, our research suggests that humans co-existed with Pleistocene animals. At La Chimenea (Figure 19.14), discovered by Steve Gerrard and Nancy de Rosa and reported to one of us (J.A.), fossil bones of the camelid Hemi-auchenia macrocephala had been partially burned as a result

any evidence of a fusion. The parietal is more rounded than in adult individuals of the research area. Inferior and superior temporal lines are undeveloped, and in the occipital, muscu-lar incisions are shallow. We therefore preliminarily interpret the Pit II individual as an infant, or juvenile.

Discussion and ConclusionsThe database for human remains of Preceramic age in the submerged caves of Quintana Roo, South Mexico, is steadily

Figure 19.13 Underwater archaeologist collecting human skull fragment from 30 m deep at Cenote Pat Jacinto (formerly known as El Pit).

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Figure 19.14 Bones of paleollama Hemiauchenia macrocephala collected at La Chimenea site. Evidence suggests preceramic settlers may have eaten this species.

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of roasting in an ancient hearth. The final extinction of Hemi-auchenia in North America has been dated to 13,300–12,900 cal yr BP (e.g., Haynes 2006; Fiedel and Haynes 2004), a pe-riod consistent with the extinction of other large mammals found in the caves. The collapse of megafaunal populations may even have occurred between 14,800 and 13,700 cal yr BP (Gill et al. 2009). Charcoal concentrations interpreted by us as hearths are also found in water depths of up to 30 m and were dated by 14C to 8941 ± 39 yr BP and 7740 ± 39 yr BP at Las Palmas. At Aktun Ha, discovered by J. Coke and reported to us by O. Río, a small cavity in an isolated rock about 0.9 m above the cave ground had been used as a hearth. Charcoal samples from this niche were dated by 14C to 9139 ± 23 yr BP and 9180 ± 60 yr BP. Hearths clearly required a dry cave. The cenote humans thus populated the area at a time when caves reaching to 30 m and more below present water level were still dry and unaffected by the post-Pleistocene rise of sea level. It is known that present-day water levels were reached about 6600 yr BP (Blanchon and Shaw 1995; Ga-briel et al. 2009). The corpses of these individuals could have floated to their present locations, but this latter scenario ap-pears unlikely for the following reasons:

1) Human skeletons are found in deep parts of the caves, hundreds of meters from the nearest entrance. If the caves were water filled the corpses would have to drift several hundreds of meters, through a cave system of tunnels and open galleries decorated with spelo-themes, and be subsequently deposited almost com-plete (> 80% of bones were recovered).

2) Four of the eight (El Templo, Las Palmas, Chan Hol I, and Chan Hol II) were found almost fully articulated, without major bone displacement, with even with the anatomical connections of carpals and tarsals intact. These structures are the first to disintegrate and slough off a body floating in water for a long time (Haglund and Sorg 2002). This situation clearly indicates the bod-ies decayed in situ, which only could have occurred in a dry cave. Moreover, the flexed positions of the Naha-ron, Las Palmas, Chan Hol I, and Chan Hol II, and pos-sibly Muknal individuals were intentionally deposited, likely in a funeral, which would also require a place that was dry at the time. At El Pit I and El Templo this situa-tion is less clear. The final disposition of the skeletons appears to be the result of accidental death in the case of El Templo, and water-run-off for El Pit I.

Human skeletons from the drowned caves of the Yucatan peninsula are dated to the Pleistocene-Holocene transition and are thus among the earliest settlers of the American con-tinent known from bone material. The physical morphology of their crania should give evidence for their evolutionary re-lationship with subsequent settlers in the area such as the pre-Hispanic cultures that populated Mesoamerica during the middle and late Holocene. In this context, the so-called Paleoamerican morphol-

ogy is characterized by a narrow and low neurocranium, low orbits, and a wide nasal region (Neves and Hubbe 2005). The face is generally low relative to the height of the neuro-cranium, and the upper face region is unflattened. In the fos-sil record this morphology is present in extensive collections from the Lagoa Santa region of Brazil, in the oldest human remains from the Sabana de Bogotá region in Colombia, and in crania from the Mexican basin (González-José et al. 2005; Neves et al. 2007). Populations with these characteristics are known to exist up to the late Holocene in isolated regions of Patagonia and on southern Baja California (González-José et al. 2003). The Amerindian morphology, on the other hand, is de-fined by bulged crania (brachicranial) and a wide and flat-tened face, principally in the medium and upper region (Pucciarelli 2004). These characters are found in almost all modern indigenous groups in the Americas (Pucciarelli 2004) and in mongoloid populations from China and other regions of northern Asia (Cunningham and Jantz 2003). The dichotomous recognition of Paleoamerican and Am-erindian morphologies in ancient cultures of the American continent has led some authors to postulate a “two-compo-nent model” (Pucciarelli 2004), in which the continent was first colonized by groups emigrating from southern Asia. They would be the ancestors of modern “Australomelanesian” groups and could have migrated to America along the Bering passage, approximately 12,000 years ago. Their cranio facial shape changed little and their demographic growth rate in America remained low. According to this model, the Paleo-americans were replaced about 9000 years ago by a second migration wave of Amerindian groups. The replacement was exceedingly fast and apparently occurred without genetic interchange between the two cultural groups (Pucciarelly 2004). The model thus postulates that a clear discontinuity exists between the fossil remains of two distinct but homog-enous human groups populating the same territories within the Americas: the Paleoamericans with a minimum age of 9000 years, and the Amerindians, which are younger. Following this model, the Las Palmas, Naharon, Muknal and El Pit individuals would be of Paleoamerican genetic stock and thus should resemble fossil humans from the Mexican basin, Lagoa Santa, as well as modern Australomelanesian groups, and they should differ from historic and modern Ma-yan populations. This is only partially the case: Even though cranially diverse, the preceramic individuals from the Yucatan submerged caves are indeed characterized by mesocrania with low orbits, narrow faces and variable nose apertures, whereas Maya populations from the same region present a marked hyperbrachycephaly (very rounded skulls), hypso- to orthocrania hipertapeinocrania (wide, short and low skulls), and facial regions eurienas (broad), mesorrinas (intermedi-ate nose width), hipsoconcs (low orbits) and mesognats (flat faces) (Tiesler 2012). These differences, however, are not suf-ficiently pronounced to exclude the possibility that the late-Pleistocene individuals may indeed be ancestors of the pre-Hispanic Maya.

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As a minimum, although the Las Palmas, Naharon and Muknal individuals show important inconsistencies within the so-called Paleoamerican morphology, nonetheless they do not coincide with Amerindians either. The individu-als from submerged caves have mesocranial skulls, with an overall shape and size outside the dimensions of the Lagoa Santa, Sabana de Bogotá, and Basin of Mexico collections. They rather resemble other early-Holocene skulls from North America, such as those from Pelican Rapids, Florida; Gordon Creek, Colorado; Marmes, Washington (Young and Steele 1987); and Buhl, Idaho (Herrmann et al. 2006), all of which are mesocranial and show a greater variability than their counterparts from South America (multivariate analysis shows clearly the variability of “Paleoamerican” individuals from North America; Terrazas et al. in preparation). These preliminary results suggest that near the end of the Pleistocene a notable morphological diversity must al-ready have existed, which was likely the result of local micro-evolution. The early colonization of North and South America must have been a highly complex process in which disper-sion and adaptation to local environments are not fully un-derstood. The latest-Pleistocene to early-Holocene ages of the Quintana Roo individuals and their marked cranial diversity, combined with the diversity known to date for other North American “Paleoamerican” skulls, provide evidence for an early colonization of the Americas, which likely occurred prior to the appearance of the Clovis culture in the Great Plains. Likely, this diversity is the result of an earlier migra-tion wave and subsequent microevolution of these settlers in, and selective adaptation to, different environmental con-ditions of the North American continent. In that case models based mostly on migration as the driving genetic force are insufficient to explain the detailed process of settlement of the Americas.

AcknowledgmentsIdentification and registration of submerged prehistoric caves in Quintana Roo and Yucatan was only possible due to the great support of cave divers of the region. Without their collaboration and dedicated participation in our work, this research would not have been possible. We are especial-ly grateful to Steve Gerrard, Vicente Fito, Luis. F. Martínez, Karin Bouchel, Alejandro Elizondo, Marco Rotzinger, Samuel Meachan, Kate Lewis, Rogelio Mier, Luz Maria Guzman, James Hobs, Tom Vogt, Roberto Chavez, Flor de Maria Curiel, Luis Leal, Sergio Granuchi, Bernadette Carrion, Ernesto Ruiz, Val-entina Cucchiara, Nick Poole, Roberto Hashimoto, Robbie Schmittner, Germán Yañez, Octavio del Río, William Phillips, James G. Coke, Andreas Matt, Scott Carnahan, Sebastian Genijovich, Fernando Rosado, Enrique Soberanis, and Raul González. In a multidisciplinary project, the participation and support of academic collaborators from different areas is highly important. We thank; Amaru Argüesu, Javier Gonza-lez, Emilio Olguín, Teresa Olguín, Ben Mcguiver, Juan Carlos Mantilla, Claudia Luna, Joaquín García-Bárcena†, Joaquín Ar-

royo, Oscar Polaco†, Paul Blanchon. Luis Marín, Elva Escobar, Magdalena de los Ríos, Erv Taylor, Alistair Pike, Thomas High-man, Silvia González, José C. Jiménez, Mónica López Portillo, Carlos Serrano, Pilar Luna, Fernando Sánchez, Sergio Grose-jan, Felipe Bate, Ximena Chávez, Fidencio Rojas, Aldo Castro, Rodrigo González, Susana Xelhuatzin, Paolo Testelli, and Fro-ylan Rojas. Lisseth Pedroza, Sandra Damián, Raúl Cervantes, Esther Reynoso, and Lucía Ivonne Lopez were students who participated in the fieldwork. We gratefully appreciate the detailed revision and comments by editors Kelly Graf and Caroline Ketron and by two anonymous reviewers. We spe-cially thank Miguel Quintana and Grupo Xcaret. We acknowl-edge support of the project “Atlas Arqueológico Subacuático para el Registro, Estudio y Protección de los Cenotes en la Península de Yucatán” and “Estudio de los grupos humanos preceramicos de la costa oriental de Quintana Roo, México, a través de los contextos actualmente inundados” by the Insti-tuto Nacional de Antropología e Historia (INAH) and financial support by the Internationales Büro of the German Bundes-ministerium für Forschung und Wissenschaft (BMBF project 01DN119), the Rolex Award for Enterprise 2008, Dive Xtras diver propulsion vehicles and by GEO Magazine.

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