Notable: The enamel-dentine junction of surviving Zhoukoudian teeth

Notable paper: Zanolli, C., Pan, L., Dumoncel, J., Kullmer, O., Kundrat, M., Liu, W., … & Tuniz, C. (2018). Inner tooth morphology of Homo erectus from Zhoukoudian. New evidence from an old collection housed at Uppsala University, Sweden. Journal of human evolution, 116, 1-13. doi:10.1016/j.jhevol.2017.11.002

Synopsis: Zanolli and coworkers studied a small sample of teeth in Uppsala that had been taken to Sweden by Otto Zdansky in the 1920s. Being held in Sweden, these teeth escaped the loss of the rest of the Zhoukoudian fossils during the Second World War. Zanolli’s team carried out CT scanning of the fossils and studied their enamel-dentine junction (EDJ). This part of the internal structure of the tooth reflects the initial stages of development of the tooth crown, and can preserve evidence of anatomy even as the occlusal surface of the tooth develops wear.

Interesting because: The results suggest that Chinese H. erectus may have been taking a different evolutionary pathway from H. erectus in Indonesia. Zanolli and coworkers emphasize that an Indonesian H. erectus sample from later in the Middle Pleistocene, from Ngandong, has “simplified” EDJ morphology compared to earlier Indonesian samples. Zhoukoudian teeth have a more similar form to earlier Indonesian teeth than to Ngandong teeth, even though the Ngandong teeth are more similar in age. That difference might just be teeth, although the cranial and mandibular morphology also shows some consistent differences between Zhoukoudian and Ngandong, as evident since Franz Weidenreich studied the samples. This may be a sign of deep population divergences and history within the sample long known as Asian H. erectus.

Evolutionary connections: As pointed out in this paper, Yousuke Kaifu and colleagues (2015) examined the EDJ morphology of Homo floresiensis teeth, and concluded that they reflected a very simplified form compared to H. erectus. That seems to be a similarity with later H. erectus specimens from Java like Ngandong. That’s interesting in light of the observations by Debbie Argue and coworkers (2017) and Mana Dembo and colleagues (2016) that H. floresiensis seems to be deeply rooted in the phylogeny of Homo and not closely related to Indonesian H. erectus.