**3. A possible migration route estimated from the Phylogenetic studies of Paleolithic Ryukyu Islanders**

**137**

*The Migration, Culture, and Lifestyle of the Paleolithic Ryukyu Islanders*

bone remains, and there are many Pleistocene fossil sites. Paleolithic research in the Ryukyu Islands began with the discovery of human bone fragments that were mixed with extinct animal fossils in several karstic caves [13]. After the discovery of these partial human fossils, researchers began an exhaustive survey for Paleolithic human remains. In 1970, four well-preserved adult human fossils were discovered at the Minatogawa site, Okinawa Island. The Minatogawa human fossils were about 20,000 years old based on the Carbon-14 dating of the charcoal obtained in their vicinity (**Figure 2**) [14, 41, 42]. Their morphological features and phylogenetic positions were investigated primarily through morphological studies. The Minatogawa human had many morphological traits such as relatively short stature, short clavicles, and a slender upper body with relatively robust lower limb bones. They differ from those of Jomon people, the Holocene hunting-gathering-fishing people who lived in the Japanese Archipelago including the Ryukyu Islands, from 3000 to 15,000 years ago [43–45]. Despite these differences, the Minatogawa people were previously considered ancestors of Jomon and modern Japanese people, based mainly on the morphological characteristics of the

In the 2000s, researchers conducted a more detailed comparison of the Minatogawa human fossils and a relatively larger sample of Jomon and modern Japanese people using newly developed methods such as three-dimensional scanning and computed tomography. These studies indicated that there are many differences between the Minatogawa humans and the Jomon/Modern Japanese people even in the skull morphology, including the length and thickness of tooth roots [46], the three-dimensional morphology of the glabellar region [47], the shape of the braincase [48], and the mandible shapes [49]. If there are so many differences, we may need to reconsider the traditional hypothesis that the Minatogawa people

Genetic analysis of modern Okinawan people also suggests the weakness of the relationship between the Pleistocene and Holocene populations of the Ryukyu Islands. Sato et al. indicated that modern Okinawan people diverged from the continental group (Han Chinese) more recently than 15,000 years ago, based on a comparison of the modern Okinawan genome [50]. If so, the Paleolithic people who had lived in the Ryukyus before this divergence would have little or no genetic

Then, is there an affinity between the Minatogawa people and the surrounding populations? Kaifu et al. suggested that their slender mandible morphology may be similar to that of the modern Australo-Melanesian who are found throughout parts of Southeast Asia and Oceania today [49]. A morphological study of the recently unearthed 27,000-year-old human skull from Shiraho-Saonetabaru Cave in Ishigaki Island suggests a possible relationship between Paleolithic Ryukyu Islanders and prehistoric Southeast Asians. Kono et al. pointed out that the Paleolithic skull of the Shiraho-Saonetabaru showed a morphological similarity to that of the Mesolithic Vietnamese [51]. This result coincides with the results of ancient mtDNA analyses of two other Paleolithic human bone fragments obtained from the same site. The haplotypes B4 and R were obtained in the mtDNA analyses [52]. The current center of the distribution of haplotype B4 is in Southeast Asia, and that of haplotype R is an ancestral haplotype of the haplogroup that includes European, Southeast Asian,

In summary, these results indicate that Paleolithic people traveled to the Ryukyu Islands through Southeast Asia after leaving Africa. They appear to have little or no similarity with the Holocene populations of the Japanese Archipelago in terms of morphological and genetic traits. However, morphological and genetic research of Paleolithic people from this area is still underway. The recent excavation at Sakitari

were a direct ancestor of Jomon and modern Japanese people.

contribution to the present population of Okinawa.

and Australian Aboriginal people [52].

*DOI: http://dx.doi.org/10.5772/intechopen.92391*

skull [14, 44, 45].

Limestone is widely dispersed throughout the Ryukyu Islands, especially in the southwestern half of them. Karstic caves are well suited for preserving

#### *The Migration, Culture, and Lifestyle of the Paleolithic Ryukyu Islanders DOI: http://dx.doi.org/10.5772/intechopen.92391*

*Pleistocene Archaeology - Migration, Technology, and Adaptation*

gradually shifted from Sino-Japanese species to Oriental species from the north to the south. The basis of the terrestrial fauna was formed before the isolation from

*Overviewed stratigraphy of the Minatogawa site. The uppermost part of the fissure deposit contained Holocene Jomon. The lower level (layers III and IV) contained late Pleistocene animal and human fossils. Although only medium-sized animals are drawn in the figure, many small animal fossils were found in the lower deposit.*

animals. Today, the fauna of the Ryukyus consists of many endemic small animals but lacks large and middle-sized animals except for the wild boar. The late Pleistocene fauna throughout the islands has not been studied thoroughly; it has only been cursorily reviewed by several authors [31–33]. The consensus is that the Pleistocene fauna was similar to the existing fauna of each island. There were several middle-sized animals that are now extinct: one or two species of middle-sized deer and a species of middle-sized tortoise. They became extinct almost simultaneously at the end of the Pleistocene, but the precise timing of extinction is not known yet. The flora of the Pleistocene Ryukyus was shrouded in mystery. Kuroda and Ozawa (1998) studied pollen samples obtained from a boring core specimen extracted from Izena Island, which is northwest of Okinawa Island [34]. They suggested that the evergreen broad-leaved forest reduced in size and the pine tree became dominant during the LGM. However, the composition of the terminal-Pleistocene fossil-amphibian species of the southern area was similar to the modern fauna of the northern broad-leaved evergreen forest area of Okinawa Island [35]. A dominance of forest species is also reported among avifauna [36, 37], reptiles, and mice [38–40] at the Minatogawa site, a terminal-Pleistocene site of Okinawa Island (**Figures 1** and **2**, **Table 1**). Based on the composition of these fossil species, we can assume that a large area of Okinawa Island was covered with a broad-leaved ever-

Nearly two million years of isolation have fostered many of the islands' endemic

the Eurasian Continent in the early Pleistocene [29–31].

green forest during the late Pleistocene and even the LGM period.

**Paleolithic Ryukyu Islanders**

**3. A possible migration route estimated from the Phylogenetic studies of** 

Limestone is widely dispersed throughout the Ryukyu Islands, especially in the southwestern half of them. Karstic caves are well suited for preserving

**136**

**Figure 2.**

bone remains, and there are many Pleistocene fossil sites. Paleolithic research in the Ryukyu Islands began with the discovery of human bone fragments that were mixed with extinct animal fossils in several karstic caves [13]. After the discovery of these partial human fossils, researchers began an exhaustive survey for Paleolithic human remains. In 1970, four well-preserved adult human fossils were discovered at the Minatogawa site, Okinawa Island. The Minatogawa human fossils were about 20,000 years old based on the Carbon-14 dating of the charcoal obtained in their vicinity (**Figure 2**) [14, 41, 42]. Their morphological features and phylogenetic positions were investigated primarily through morphological studies. The Minatogawa human had many morphological traits such as relatively short stature, short clavicles, and a slender upper body with relatively robust lower limb bones. They differ from those of Jomon people, the Holocene hunting-gathering-fishing people who lived in the Japanese Archipelago including the Ryukyu Islands, from 3000 to 15,000 years ago [43–45]. Despite these differences, the Minatogawa people were previously considered ancestors of Jomon and modern Japanese people, based mainly on the morphological characteristics of the skull [14, 44, 45].

In the 2000s, researchers conducted a more detailed comparison of the Minatogawa human fossils and a relatively larger sample of Jomon and modern Japanese people using newly developed methods such as three-dimensional scanning and computed tomography. These studies indicated that there are many differences between the Minatogawa humans and the Jomon/Modern Japanese people even in the skull morphology, including the length and thickness of tooth roots [46], the three-dimensional morphology of the glabellar region [47], the shape of the braincase [48], and the mandible shapes [49]. If there are so many differences, we may need to reconsider the traditional hypothesis that the Minatogawa people were a direct ancestor of Jomon and modern Japanese people.

Genetic analysis of modern Okinawan people also suggests the weakness of the relationship between the Pleistocene and Holocene populations of the Ryukyu Islands. Sato et al. indicated that modern Okinawan people diverged from the continental group (Han Chinese) more recently than 15,000 years ago, based on a comparison of the modern Okinawan genome [50]. If so, the Paleolithic people who had lived in the Ryukyus before this divergence would have little or no genetic contribution to the present population of Okinawa.

Then, is there an affinity between the Minatogawa people and the surrounding populations? Kaifu et al. suggested that their slender mandible morphology may be similar to that of the modern Australo-Melanesian who are found throughout parts of Southeast Asia and Oceania today [49]. A morphological study of the recently unearthed 27,000-year-old human skull from Shiraho-Saonetabaru Cave in Ishigaki Island suggests a possible relationship between Paleolithic Ryukyu Islanders and prehistoric Southeast Asians. Kono et al. pointed out that the Paleolithic skull of the Shiraho-Saonetabaru showed a morphological similarity to that of the Mesolithic Vietnamese [51]. This result coincides with the results of ancient mtDNA analyses of two other Paleolithic human bone fragments obtained from the same site. The haplotypes B4 and R were obtained in the mtDNA analyses [52]. The current center of the distribution of haplotype B4 is in Southeast Asia, and that of haplotype R is an ancestral haplotype of the haplogroup that includes European, Southeast Asian, and Australian Aboriginal people [52].

In summary, these results indicate that Paleolithic people traveled to the Ryukyu Islands through Southeast Asia after leaving Africa. They appear to have little or no similarity with the Holocene populations of the Japanese Archipelago in terms of morphological and genetic traits. However, morphological and genetic research of Paleolithic people from this area is still underway. The recent excavation at Sakitari

#### **Figure 3.**

*Section of trench I and pit 1 of Sakitari cave. Partial human remains and animal remains consumed by humans were obtained from layers I to III. Artifacts were unearthed from layers I and II (see also Figure 4).*

Cave indicates that Paleolithic people occupied Okinawa Island almost continuously from 30,000 to 13,000 years ago (**Figure 3**). Studies of the other Paleolithic individuals excavated from Shiraho-Saonetabaru Cave and the human bones recently discovered in Sakitari Cave near the Minatogawa site will provide insight into this problem in the near future.
