Electronic Supplementary Material for Dental development in Homo naledi from Dental development in <i>Homo naledi</i>
2017-08-16T15:28:51Z (GMT) by
Humans’ prolonged somatic development and life history are unique among primates, yet their evolutionary origins remain unclear. Dental development has been used as a proxy to reconstruct life-history evolution in the hominin clade and indicates a recent emergence of the human pattern. Here, we analyse tooth formation and eruption in two developing dentitions of <i>Homo naledi</i>, a late-surviving, morphologically mosaic hominin species. Deciduous dental development is more similar to humans than to chimpanzees, likely reflecting hominin symplesiomorphy rather than bearing life-history significance. The later stages of permanent tooth development present a mix of human- and chimpanzee-like patterns. Surprisingly, the M<sub>2</sub> of <i>H. naledi</i> emerges late in the eruption sequence, a pattern previously unknown in fossil hominins and common in modern humans. This pattern has been argued to reflect a slow life history and is unexpected in a small-brained hominin. The geological age of <i>H. naledi</i> (approx. 300 kya), coupled with its small brain size and the dental development data presented here, raise questions about the relationship between dental development and other variables associated with life history.