Abstract:

The Hualongdong (HLD) site is situated in Wangcun Village, Yaodu Town, Dongzhi County, Anhui Province, China, on the southern slope of Meiyuan Hill. The site is characterized by a collapsed cave comprising carbonate-cemented cavern breccia, unconsolidated clay and gravel. It was discovered in late 1988. Following several excavation campaigns between 2006 and 2024, approximately 20 human individuals, more than 400 artificial stone tools, numerous bone fragments with signs of manual cutting and chopping, and over 80 species of animal fossils have been uncovered. These findings date back to between 331,000 and 275,000 years ago.

In this paper, we carried out facial restoration on the HLD No.6 skull fossil unearthed at this site. The HLD 6 hominid skull was found in 2015. When unearthed, the skull was broken into 20 fragments of different sizes, among which 7 were wrapped in a large cementing material, and the other 13 dispersed around the large cementing material. According to the bone thickness, bone sutures, cross-sections, the middle cerebral artery and the occlusal state of the teeth, a three-dimensional model of the HLD skull was 3D virtual restored. After reconstruction, it preserves almost entire face, most of the mandibular and a largely cranium.

To show the pre-life appearance of HLD hominid, according to the relationship between facial bones and soft tissues, a manual method was adopted to reconstruct the outer surface of the skull with muscle, skin, and facial features using plasticized materials (silly putty and plaster) on the 3D virtual reconstruction of the 3D printed skull model. After craniofacial reconstruction, the HLD hominid showed more modern human features with a flat glabella, a backward forehead, a flat face, and the appearance of a chin, however, it still retained some archaic features such as a developed brow ridge, a low cranial height. The HLD human fossils exhibit a mix of physical characteristics transitional between Homo erectus and modern humans. The cranium displays more primitive traits, the facial structure resembles that of modern humans, and the mandible shows early signs of modern human chin. Compared with the "pre-Homo sapiens" Jebel Irhoud found in Morocco, Africa, dated to the same age, the two show similar transitional physical features from archaic to Homo sapiens. The HLD hominin fossils provide crucial evidence of the diversity of late Middle Pleistocene human evolution in East Asia, indicating that modern forms related to Homo sapiens emerged in this region around 300,000 years ago.

Key words: Hualongdong site, Middle Pleistocene, human fossil, craniofacial reconstruction, East Asia