The History of Our Tribe Hominini Textbook Part IV Pleistocene Epoch Chapter 19 Paranthropus robustus

19 . beside human I robust ) Figure . photograph by Mike Peel ( is licensed under . SITES , and Coopers Cave , South Africa PEOPLE Robert Broom and Andre Keyser 131 INTRODUCTION In 1938 , Robert Broom discovered the first material at the site of , South Africa . He later found material at , and because the molar teeth were more primitive at that site , he changed the species name at to but used for the material . Molar characteristics from the more recent material from the site are thought to be intermediate between the and molars , and most researchers now consider the material from all three sites to be species . PHYLOGENY Au . is the favored ancestor of . However , others believe that and are descended from Au . Of the former school , some believe that is also descended from Au . and thus a sister species to . The two species would then have inherited their flexed skull base from Au . Like , appears to be an evolutionary dead end . DISCOVERY AND GEOGRAPHIC RANGE The species is known only from sites within the Cradle of Humankind World Heritage Site in South Africa . As mentioned in the introduction , Robert Broom discovered the first material at and subsequent specimens at the site of . Andre Keyser discovered the jaw and dental material at in 1994 . PHYSICAL CHARACTERISTICS Like , exhibited of the skull , face , and mandible orthognathism in that the teeth were tucked under the cranial base small anterior dentition large muscles of mastication large zygomatic arches for passage of the muscle sagittal crests in males and a nuchal crest that did not converge with the sagittal crest tall mandibular rami to increase the strength of the masseter and medial pterygoid ( another muscle of mastication ) muscles for their tough , fibrous diet and a large mandibular body and a high degree of postorbital constriction due to their large face ( see skull cast in Figure ) Characteristics shared with Au . are a flexed skull base , molars were 17 larger , but their of was lower ) a larger second than third molar , and facial . While appears to have been more orthognathic than Au . they were not . Their anteriorly oriented orbits and reduced the distance between their and jaws , making it appear so . The nasal bones were recessed relative to the , so that they too had a somewhat like Au . They had less of a forehead than Au . because of the orbits . Finally , unlike Au . where maximum force was on the molars , the maximum force was on the due to a combination of the forward placement of the and an enlarged anterior portion of the muscle that was offset by the positioning of the dental arcade under the ( and Smith 2009 ) Average cranial capacity is estimated to have been 530 , giving them the highest , of any pith ( and Smith 2009 ) The morphology of shares some similarities with Homo , such as broad distal finger phalanges that are thought to indicate enlarged tactile pads and increased vascularization , sensitivity , and motor control , as well as a large attachment for the flexor muscle that acts as a powerful thumb flexor . They thus are thought to have had a great degree of manual dexterity and were likely capable of making and certainly using tools . However , they retained some primitive characteristics , 132 The History of Our Tribe

including long arms small vertebral bodies , especially inferiorly small sacroiliac and hip joints more oriented ilia and a long femoral neck . Males of the species are thought to have stood ( tall and weighed 120 ( 54 ) and females , 32 ( and 90 ( 40 ) Review of Primitive Characteristics Retain prognathism , concave facial profile , long arms , small vertebral bodies , small sacroiliac joints , ilia , and long femoral neck of Au . Review of Derived Characteristics Same characteristics as , except not as robust and large . Maximum bite force on . ENVIRONMENT AND WAY OF LIFE Like , are thought to have been generalist herbivores that may have consumed some mal matter and could fall back on hard and brittle items , such as nuts , seeds , and fruits , when preferred items were not available . Brain found wooden digging sticks in association with remains . In addition , polish on bone and horn cores ( bone interior of animal horns ) attributed to is consistent with repeated digging , such as for tubers . Of interest is recent research that indicates that they were more than , supporting the notion that we have inherited the chimp and bonobo pattern of females relocating to join and range with a group of males . Amazingly , isotopic analyses of strontium in their teeth indicates that females did not grow up where their fossils are found ( et al . 2011 ) 19 . 133