Chinese archeologists have renewed investigation at the late Miocene hominoid digs in Yunnan, southwest China, according to archeologists at the the international anthropology forum on Thursday.

"We wanted to recover additional fossil hominoids and obtain further detailed information on their paleontological, geological, and paleoecological contexts," said Ji Xueping, an archeologist from the Department of Vertebrate Paleontology and Paleoanthropology, Yunnan Institute of Cultural Relics and Archaeology, on the sideline of an international forum on anthropology on Thursday.

Up till now, late Miocene and Pliocene hominoids have been recovered from four sites in Yunnan. One of the most prolific of these dig sites is Leilao in the Yuanmou basin, 110 kilometers northwest of Kunming, capital of Yunnan. More than 300 hominoid specimens have been recovered at Leilao belonging to Lufengpithecus and Yuanmoupithecus, two generations of the extinct apes dating eight million to two million years ago, Ji said.

The evolutionary position of Lufengpithecus has been contentious among archeologists. Some suggest that Lufengpithecus is a primitive hominid while others believe it to bear affinities to Ponginae, a primate.

"We tend to favor that Lufengpithecus is a primitive Ponginae," Ji said, adding that they are doing more comprehensive comparative analysis to substantiate their conclusion. "It is still under debate and there is no final conclusion yet."

Ji is working on the study with anthropology professor Terry Harrison from the Center for the Study of Human Origins and his colleague Zheng Liang.

Hominoids at Leilao were first discovered in 1990 by a group of Chinese archeologists and excavations were carried out in 1999. The digs unearthed nearly a hundred hominoid teeth and two mandibular fragments.

Renewed excavations were conducted at Dashuqingliangzi near Leilao and at Liujianfang near Leiyi, about 1.5 km northwest of Leilao from December 2006, he said.

The collection obtained includes 99 specimens of Lufengpithecus and two specimens of Yuanmoupithecus.

The fossil apes recovered in Yunnan provide an important perspective on the evolutionary history of hominoids. Their continued occurrence during the late Miocene and Pliocene, when hominoids became extinct throughout the rest of Eurasia, suggests that southern China was an important refugium for hominoids.

Previous study by the team, led by Harrison, suggests the uplift of the Tibetan plateau and its impact on regional climate may have been an important contributing factor in isolating the hominoids geographically and ecologically.

They speculate that the changed climate condition in the mid-Pliocene, about 3 million years ago, and possibly the subsequent emergence of Homo may have caused the regional extinction of large hominoids in southern China and in mainland Southeast Asia.

"Our future excavations and collections at Leilao will focus on an improved understanding of the phylogenetic relationships, paleobiology, paleoecology and taphonomy of the fossil hominoids," he said.

(Xinhua News Agency July 31, 2009)