An ancient human fossil discovered from the seafloor near Taiwan reveals that a primitive group of humans, potentially an unknown species, once lived in Asia, researchers say.

These findings suggest that multiple lineages of extinct humans may have coexisted in Asia before the arrival of modern humans in the region about 40,000 years ago, the scientists added.

Although modern humans, Homo sapiens, are the only surviving human lineage, others once walked the globe. Extinct human lineages once found in Asia include Neanderthals, the closest extinct relatives of modern humans; Denisovans, whose genetic legacy may extend from Siberia to the Pacific islands of Oceania; Homo erectus, the most likely ancestors to modern humans; and the hobbitlike Homo floresiensis, who lived in Indonesia. These all are hominins — the group of species consisting of humans and all their relatives after the split from the chimpanzee lineage. [The 10 Biggest Mysteries of the First Humans]

Now, scientists have revealed the first ancient human fossil — a nearly complete right side of a lower jaw with primitive-looking teeth — to be found in Taiwan.

The fossil was dredged by a fishing net from the seafloor about 200 to 400 feet (60 to 120 meters) below the surface of the Penghu Channel, located about 15.5 miles (25 kilometers) off the western coast of Taiwan. The channel was part of the Asian mainland during the last ice age, when sea levels were lower.

An unknown fisherman sold the fossil, now dubbed Penghu 1, to a local antique shop. A local collector later submitted Penghu 1 to Taiwan's National Museum of Natural Sciences after the researchers noticed its significance.

Analysis of trace elements in Penghu 1 suggests the hominin probably lived between 10,000 and 190,000 years ago. The jaw and its teeth look unexpectedly primitive for this age, the researchers said. During the Pleistocene Epoch, which lasted from about 2.6 million years ago to 11,700 years ago, humans generally evolved smaller jaws and teeth, but the new fossil from Taiwan appears larger and more robust than older Homo erectus fossils from Java and northern China.

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The researchers said Penghu 1 does resemble a 400,000-year-old fossil from Hexian, in southern China, located about 590 miles (950 km) north of the Penghu Channel. The scientists suggest these fossils together represent a distinct group of archaic humans, although they caution that they do not yet have enough evidence to say whether it is a new species or not.

"We need other skeletal parts to evaluate the degree of its uniqueness,"study co-author Yousuke Kaifu, a paleoanthropologist at Japan's National Museum of Nature and Science in Tokyo, told Live Science. "The question of species can be effectively discussed after those steps."

The new findings suggest there were several different groups of archaic humans living in Asia at the same time, some more primitive than others. "Then modern humans dispersed into this region around 50,000 to 40,000 years ago and came across a diverse group of hominins," Kaifu said. "This is a very different, complex and exciting story compared to what I was taught in school."

The scientists detailed their findings online today (Jan. 27) in the journal Nature Communications.

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