Japanese Pleistocene Landbridges
and the Earliest Watercraft

Home | Index by Charles T. Keally
March 20, 2005
last revised: October 9, 2010


Understanding the first settlement of the Japanese islands requires, among other things, knowledge of the dates of landbridges connecting the islands to the Asian continent and the dates for the earliest evidence of watercraft.

Today, Japan consists of four main islands and two major chains of small islands. The main islands from north to south are Hokkaido, Honshu, Shikoku and Kyushu. The island chains are the Nampo Shoto (Izu-Ogasawara) chain, extending from the Tokyo Bay-Izu Peninsula area to the Mariannas, and the Nansei Shoto extending from the southern end of Kyushu to Taiwan. The Nansei Shoto has two parts: the Satsuma group of islands in the north, and the Ryukyu group of islands in the middle and south. The Satsuma group (Tanegashima, Akushima, Amami Oshima) is part of Kagoshima Prefecture at the southern end of Kyushu. The Ryukyu group is Okinawa Prefecture, and it has two parts: the main Okinawa group of islands (the middle of the Nansei Shoto chain) and the Sento group of islands (the Miyako, Ishigaki and Yaeyama island clusters, the southern end of the Nansei Shoto chain).

At times of lowered sea levels, the main islands of Honshu, Shikoku and Kyushu usually were connected in one landmass, called Hondo, mainland or main islands.

Japan is separated from the continent by the Sea of Japan (Hokkaido and Honshu), the Tsushima and Korean straits (western Honshu and Kyushu) and the East China Sea (Kyushu and the Ryukyuan chain). In the north, Hokkaido is separated from Sakhalin Island by the Soya Strait. The Kurile Island chain extends northeastward from the eastern tip of Hokkaido to the Kamchatka Peninsula in northeastern Russia. And the Pacific Ocean borders the whole eastern side of the Japanese islands.


The methodology for studying past landbridges between the Japanese islands and the continent relies broadly on four types of information: (1) palaeonotology (immigrant land animals), (2) sea-level changes, (3) sea-floor topography, and (4) salinity and marine-faunal changes in the East China Sea and the Sea of Japan.

The methodology for studying early evidence for watercraft presently relies primarily on evidence of humans on islands that never were connected to a continental landmass, or close cultural similarity across a strait that was a water connection throughout the Pliocene and Pleistocene.


General: According to Dobson and Kawamura (1998), Japanese Hondo was connected to the Asian continent via a landbridge three times in the Pleistocene, about 1.0 Ma, about 500 ka and about 300 ka, evidenced by the immigration of large land animals from the continent. These three landbridges are identified by the immigration of Mammuthus shigensis from the north (in China), Stegodon orientalis from the south via the East China Sea continental shelf, and Palaeoloxodon naumanni from northern China via the Korean peninsula (Kawamura 1998: 252-255; see also Matsufuji 2002, 2004).

(Note that the dates 500 ka [ka=1,000 years] and 300 ka are now generally thought to be 630 ka and 430 ka [Kawamura 2001: 40, citing Konishi & Yoshikawa 1999; Taruno 2010].)

In 1989, Kawamura et al. (1989: 317, 324) said that the number of species immigrating to Hondo from the continent in the late Middle Pleistocene (about 300 ka to about 120 ka) was few, but the recent literature appears to agree that in fact NO land animals immigrated to Hondo from the continent after about 430 ka. However, there remains a small possibility that very short-lived land bridges did appear during the Middle Pleistocene, roughly 100 ka to 800 ka (Taruno 2010), one about 130 ka (Takahashi 2007).

Honshu-Hokkaido: Hondo and Hokkaido were connected via a landbridge about 500 ka and about 300 ka [now given as 630 ka and 430 ka], seen in the immigration of land animals from Hokkaido to Hondo (Dobson & Kawamura 1998). During the time of the landbridge between Hondo and Hokkaido ca. 300 ka [now ca. 430 ka], Palaeoloxodon naumanni and Sinomegaceros yabei entered Hokkaido from the south (Kawamura 1998: 255). In fact, Palaeoloxodon naumann possibly migrated to Hokkaido twice from the south, the second time about 30 ka across the Tsugaru "ice bridge" or by swimming (Takahashi et al. 2004).

Hondo and Hokkaido were connected a third time during the last glacial period, with migration of only large land animals moving across the "ice bridge" that formed on the narrowed Tsugaru Strait. These animals included Alces alces, Bos primigenius, Bos priscus, Ursus arctos, Equus (Kawamura et al. 1989, Table 1, pp. 320-322, p. 323). Humans also crossed the Tsugaru Strait from Honshu to Hokkaido at least as early as 20-22 ka, and possibly as early as 30-35 ka, but there is no evidence to know whether they crossed the "ice bridge" like the large animals or whether they used watercraft.

Hokkaido-Continent: Hokkaido was connected to the continent via Sakhalin Island during most of the Late Pleistocene, about 100-10 ka, with land mammal migration moving from the continent to Hokkaido. During the late Late Pleistocene, Mammuthus primigenius entered Hokkaido from the north (Kawamura 1998: 255; Takahashi et al. 2004, Table 5, p. 175).

Ryukyuan Islands-Continent/Kyushu: There is disagreement about land connections between the Ryukyuan islands and the continent or Kyushu. Kawamura (1998: 255) says that the northern Ryukyu (Okinawa and north) fauna are all endemic species from pre-Pleistocene, suggesting there were no Pleistocene landbridges connecting these islands to the continent or Kyushu, but the southern Ryukyu islands (Miyako group) have endemic species plus immigrants that arrived via landbridges in the Middle and Late Pleistocene.

Ujiie (1998: 247, 249), on the other hand, claims there was a landbridge from Taiwan to Amami Oshima ca. 75-12 ka BP [Amami Oshima is at the northern end of the middle group of Ryukyuan islands], based on 18O quantities, planktonic foraminifer and AMS 14C dates, and analysis of salinity. This landbridge disappeared in the Late Glacial due to both sea level rise and tectonic uplift. The changes noted by Ujiie, however, could result from changes in the Black Current/Kuroshio resulting from shallower waters along the Ryukyun chain and the extension southward of the northern cold current, Oyashio.

Tsushima Strait: A major question concerning landbridges is the existence, or non-existence, of a landbridge between western Japan and Korea in the Late Pleistocene. This question focuses on the Tsushima and Korean Straits. According to Matsui et al. (1998: 231) the inflow of marine water into the Sea of Japan through the Tsushima Strait was greatly reduced at the LGM, 19-15 ka [the dates apparently are not calibrated]. The δ18O values in the Sea of Japan (Matsui et al. 1998, Fig. 4, p. 225) dropped from about 30 ka, reached a minimum ca. 19-16 ka, and then rose rapidly from ca. 16-15 ka; the salinity (o/oo) dropped from ca. 35-30 ka, reached a plateau ca. 25-22 ka and a minimum ca. 19-16 ka, and then rose rapidly from ca. 15 ka. The Tsushima Strait was only about 10 m deep at the LGM. (For more discussion of the Tsushima Strait during the Pleistocene, see: Tanimura 1981 and Mogi 1981.)

It is difficult to say there was no landbridge between Korea and Japan in the Late Pleistocene, but, if there was one, it was short-lived and it existed only at the peak of the last glaciation, at the LGM, long after humans had first arrived in the Japanese islands (Matsui et al. 1998: 231). Thus, any possible landbridge between western Japan and the continent in the Late Pleistocene has no bearing on the question of when humans first arrived in the islands.


The oldest certain evidence for humans using some sort of watercraft comes from Australia and Japan. Australia was settled at least by 35 ka, possibly by 50-60 ka, via water crossings from mainland Southeast Asia that would have been greater than the 30 km and 100 km gaps that existed at the LGM (Fagan 1998: 214, 219). In Japan, obsidian from Kozu Island, in the Izu Island chain, is found in sites in South Kanto around Tokyo that are dated 30-35 ka. Kozu Island has never been connected to the Japanese main islands; it has always been a water crossing.

There is possibly earlier evidence for humans crossing water. Stone artifacts found on the island of Flores in the Indonesian archipelago, and dated to about 840 ka, could have gotten into the Soa Basin on Flores at that time only if their human makers could travel across a body of water 25 km or more wide (Morwood et al. 2005: 6-7).


Landbridges existed between Japan and continental China about 1.2 Ma, 630 ka and 430 ka. And humans were in eastern Asia from the Early Pleistocene -- at Mojokerto (1.8 Ma), Sangiran (1.6-1.0 Ma) and Trinil (900 ka; Java Man) in Java, and at Nihewan (1.7 Ma), Lantien (700 ka) and Zhoukoudian (670-410 ka; Peking Man) in northern China. Thus, there would seem to be no reason why humans could not have joined the large land animals that immigrated into the Japanese islands over these landbridges in the Early and Middle Pleistocene. However, so far there is no clear, fully agreed upon evidence of humans in the Japanese islands before about 35-50 ka.

There is a need to explain why humans did not come to the Japanese islands before the Late Pleistocene. Without such an explanation, claims that the first humans did not arrive in the Japanese islands until 35-50 ka are based only on negative evidence, and given the present state of archaeological research that makes a weak argument.

During the Late Pleistocene, humans most likely would have had to use some kind of watercraft to get to the islands -- they definitely arrived before any possible, and brief, landbridge formed at the Tsushima Strait during the LGM. There is good evidence for humans using watercraft by 35-50 ka in Australia and Japan (and possible evidence for watercraft much earlier in Flores in Indonesia).

References Cited

NOTE: Japanese and Korean names are in personal name-family name order, although I prefer using their native order.

NOTE: the bibliography search focused on the Japanese Daiyonki Kenkyu (The Quaternary Research) journal because it has numerous articles on coastal change, it is readily available, and it has English abstracts for all articles and many articles in English.

NOTE: the English translations are those given in the publication, when given, hence the odd English in some translations.


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