Endocast of Sambungmacan 3 (Sm 3): A new Homo erectus from Indonesia

Abstract

A new fossil calvaria, Sambungmacan 3 (Sm 3), described in New Fossil Hominid Calvaria From Indonesia-Sambungmacan 3 by Márquez et al., this volume, yields one of the most advanced and complete endocasts yet recovered from Java. This communication provides a thorough interpretation of the external anatomical landmarks observable on Sm 3. Using computer tomography (CT) and traditional morphological measurements, our comparative paleoneurological analyses show that while Sm 3 has a mosaic of features that are similar to both Indonesian and Chinese H. erectus, it also possesses significant characters reminiscent of later hominins. These include a greater degree of asymmetry characterized by a possible left-occipital, right-frontal petalial pattern, left-right volumetric cerebral asymmetry, and marked asymmetry in Broca's cap. Moreover, the frontal lobe offers a more rounded, shortened appearance in contrast to the flat, elongated appearance of other Indonesian fossils (e.g., Sangiran 17). Another unique trait is exhibited in the transverse plane where the widest breadth of Sm 3 occurs more superiorly than in other Indonesian H. erectus. Thus, the endocast of Sm 3 presents a unique morphology not seen previously in the hominin fossil record. While the strong modern human characteristics in this endocast may not represent a particular ancestry, they do allow us to recognize a new dimension of the remarkable variation in Indonesian Homo erectus.

<i>Homo erectus</i> calvaria from Ngawi (Java) and its evolutionary implications

“…This figure is within the ranges of variation estimated for Bapang-AG (855-1059 cm 3 : Holloway, 1981;Kaifu et al, 2011a) and Sambungmacan (917-1035 cm 3 : Jacob, 1973;Broadfield et al, 2001;Baba et al, 2003), but is smaller than the Ngandong crania series (1013-1251 cm 3 : Holloway, 1980). When the 'neurocranial size variables' are compared (Figure 6), Ngawi 1 falls in the midrange of variation exhibited by Sangiran or Sambungmacan, whereas it is slightly smaller than the smallest cranium from Ngandong (Ng 7).…”

<i>Homo erectus</i> calvaria from Ngawi (Java) and its evolutionary implications

“…This figure is within the ranges of variation estimated for Bapang-AG (855-1059 cm 3 : Holloway, 1981;Kaifu et al, 2011a) and Sambungmacan (917-1035 cm 3 : Jacob, 1973;Broadfield et al, 2001;Baba et al, 2003), but is smaller than the Ngandong crania series (1013-1251 cm 3 : Holloway, 1980). When the 'neurocranial size variables' are compared (Figure 6), Ngawi 1 falls in the midrange of variation exhibited by Sangiran or Sambungmacan, whereas it is slightly smaller than the smallest cranium from Ngandong (Ng 7).…”

Solo man in question: Convergent views to split Indonesian Homo erectus in two categories

“…The shape of the encephalic rostrum (extension of the anterior regions of the first frontal convolutions) is long and narrow for African H. ergaster, as well as for Sangiran and Zhoukoudian Lower Cave H. erectus; these cerebral regions are shorter and wider on Ngandong and Sambungmacan endocasts, as confirmed by Broadfield et al (2001) on Sambungmacan 3. In relation with a large interorbital space, the encephalic rostrum is developed on the early fossil hominids, and becomes reduced on later hominids until it is no longer apparent on H. sapiens.…”

New high-resolution computed tomography data of the Taung partial cranium and endocast and their bearing on metopism and hominin brain evolution

“…and D.C.B. find no evidence for an open metopic suture, even ectocranially, in the Sambungmacan 3 Homo erectus cranium, having studied the original fossil and made endocast ourselves (30).…”

<i>Homo erectus</i> calvaria from Ngawi (Java) and its evolutionary implications

“…This figure is within the ranges of variation estimated for Bapang-AG (855-1059 cm 3 : Holloway, 1981;Kaifu et al, 2011a) and Sambungmacan (917-1035 cm 3 : Jacob, 1973;Broadfield et al, 2001;Baba et al, 2003), but is smaller than the Ngandong crania series (1013-1251 cm 3 : Holloway, 1980). When the 'neurocranial size variables' are compared (Figure 6), Ngawi 1 falls in the midrange of variation exhibited by Sangiran or Sambungmacan, whereas it is slightly smaller than the smallest cranium from Ngandong (Ng 7).…”

Solo man in question: Convergent views to split Indonesian Homo erectus in two categories

“…The shape of the encephalic rostrum (extension of the anterior regions of the first frontal convolutions) is long and narrow for African H. ergaster, as well as for Sangiran and Zhoukoudian Lower Cave H. erectus; these cerebral regions are shorter and wider on Ngandong and Sambungmacan endocasts, as confirmed by Broadfield et al (2001) on Sambungmacan 3. In relation with a large interorbital space, the encephalic rostrum is developed on the early fossil hominids, and becomes reduced on later hominids until it is no longer apparent on H. sapiens.…”

New high-resolution computed tomography data of the Taung partial cranium and endocast and their bearing on metopism and hominin brain evolution

“…and D.C.B. find no evidence for an open metopic suture, even ectocranially, in the Sambungmacan 3 Homo erectus cranium, having studied the original fossil and made endocast ourselves (30).…”

<i>Homo erectus</i> calvaria from Ngawi (Java) and its evolutionary implications

“…This figure is within the ranges of variation estimated for Bapang-AG (855-1059 cm 3 : Holloway, 1981;Kaifu et al, 2011a) and Sambungmacan (917-1035 cm 3 : Jacob, 1973;Broadfield et al, 2001;Baba et al, 2003), but is smaller than the Ngandong crania series (1013-1251 cm 3 : Holloway, 1980). When the 'neurocranial size variables' are compared (Figure 6), Ngawi 1 falls in the midrange of variation exhibited by Sangiran or Sambungmacan, whereas it is slightly smaller than the smallest cranium from Ngandong (Ng 7).…”

Solo man in question: Convergent views to split Indonesian Homo erectus in two categories

“…The shape of the encephalic rostrum (extension of the anterior regions of the first frontal convolutions) is long and narrow for African H. ergaster, as well as for Sangiran and Zhoukoudian Lower Cave H. erectus; these cerebral regions are shorter and wider on Ngandong and Sambungmacan endocasts, as confirmed by Broadfield et al (2001) on Sambungmacan 3. In relation with a large interorbital space, the encephalic rostrum is developed on the early fossil hominids, and becomes reduced on later hominids until it is no longer apparent on H. sapiens.…”

New high-resolution computed tomography data of the Taung partial cranium and endocast and their bearing on metopism and hominin brain evolution

“…and D.C.B. find no evidence for an open metopic suture, even ectocranially, in the Sambungmacan 3 Homo erectus cranium, having studied the original fossil and made endocast ourselves (30).…”