I Early Homo A At two million years ago there is East African evidence for two distinct hominin groups early Homo and A boisei the hyperrobust australopithecines which became extinct around 1 2 m y a A boisei became increasingly specialized dependent on savanna vegetation Early forms of Homo which avoided this australopithecine trend and instead increasingly relied on hunting gathering and scavenging evolved into early H erectus by 1 9 m y a B H rudolfensis and H habilis A 1972 expedition unearthed a skull designated KNM ER 1470 discovered east of Lake Rudolph Kenya 1 2 1 a b c d e a b c The 1470 skull was unusual because of its combination of a large brain 775 cm3 and very large molars Its brain size was more human than that of the australopithecine but its molars recalled those of the hyperrobust australopithecine There are problems classifying this 1470 skull Some features point to Homo while others resemble australopithecines There are problems with dating as well One estimate dates it to 1 8 m y a while another defines it as old as 2 4 m y a In 1986 1470 got its own species name Homo rudolfensis although not all paleoanthropologists accept this classification Those who consider Homo rudolfensis a valid species emphasize its contrast with H habilis Some think that rudolfensis lived earlier than and is ancestral to habilis Some think that they are simply female and male members of the same species H habilis Others think that they are separate species that coexisted in time and space Yet others think that one or the other gave rise to H erectus The debate continues The only sure conclusion is that several different kinds of hominins lived in Africa before and after the advent of Homo C H habilis and H erectus 1 2 The fossils of Homo habilis the earliest member of our genus were first found at Olduvai Gorge in Tanzania Olduvai s oldest layer dating to 1 8 m y a has yielded both small brained A boisei fossils and H habilis skulls Another important habilis find was OH62 Olduvai Hominid 62 the partial skeleton of a female H habilis This was the first find of an H habilis skull with a significant amount of skeletal material Dated to 1 8 m y a this find was surprising because of its small size and its apelike limb bones The limb proportions suggested greater tree climbing than expected This find also was surprising given what was already known about early H erectus in East Africa By that date H erectus had already attained a cranial capacity of 900 cm3 along with a modern body 3 Sister Species 4 The Significance of Hunting shape and height confirmed by a very complete young male H erectus fossil WT15 000 also known as Nariokotome boy found in West Turkana in 1986 Two recent hominin fossil finds KNM ER 42703 and KNM ER 42700 from Ileret Kenya are very significant because they show that i H habilis and H erectus overlapped in time rather than being ancestor and descendant as had been thought and sexual dimorphism in H erectus was much greater than expected ii These finds suggest that H habilis and H erectus apparently split from a common ancestor prior to 2 m y a and lived side by side in eastern Africa for perhaps half a million years Significant changes in technology occurred during the 200 000 year evolutionary spurt between 1 8 m y a and 1 6 m y a at Olduvai Tool making got more sophisticated soon after the advent of H erectus in Africa The more sophisticated tools aided in gathering and hunting These changes also affected the types of foods consumed reducing the burden on the chewing apparatus with consequences in the structure of the jaws and cranial crest As hunting became more important to H erectus encounters with large animals increased benefiting individuals with stronger skulls Cranial capacity expanded from about 500 cm3 in the australopithecines to 1 000 cm3 in H erectus which is within the modern range of variation a b a b c d e II Out of Africa I H erectus A B Biological and cultural changes enabled H erectus to exploit a new adaptive strategy gathering and hunting making possible pushing the hominin range beyond Africa to Asia and Europe Paleolithic Tools 1 2 The stone tool making techniques that evolved out of the Oldowan or pebble tool tradition that lasted until about 15 000 years ago are described by the term Paleolithic The Paleolithic or Old Stone Age has three subdivisions each roughly associated with a particular stage in human evolution a b c The Lower Paleolithic is roughly associated with H erectus The Middle Paleolithic is associated with archaic H sapiens including the Neandertals of Western Europe and the Middle East The Upper Paleolithic is associated with anatomically modern humans 3 The primary tool making tradition used by H erectus during the Lower Paleolithic was the Acheulian The Acheulian tradition included various tool types including oval shaped hand axes that were more complex than earlier Oldowan pebble tools The Acheulian tradition illustrates trends in the evolution of technology greater efficiency manufacture of tools for specific tasks and an increasingly complex technology C Adaptive Strategies of Homo erectus 1 Interrelated biological and cultural changes have increased human adaptability the capacity to live in and modify an ever wider range of environments Improved tools as well as an essentially modern skeleton permitting long distance walking and endurance allowed H erectus to increase its range and hunt more efficiently The average H erectus brain size was double that of the australopithecines and within the low range of modern humans H erectus had an essentially modern though very robust skeleton with a brain and body closer in size to H sapiens than to Australopithecus Still several anatomical contrasts particularly in the cranium distinguish H erectus from modern humans lower and more sloping foreheads large brow ridges thicker skull bones larger face teeth and jaws i Taken together the H erectus skeleton and chewing apparatus provide biological evidence of a fuller commitment to hunting and gathering Hearths found at various sites confirm that H erectus made use of fire Fire allowed H erectus to colonize a wider range of climates provided protection against predators and made cooking possible fire broke down vegetable fibers tenderized meat and killed parasites i Definitive evidence of human control of fire dates to 500 000 B P Fossils from East and West Turkana Kenya dating to 1 6 m y a including the Nariokotome boy Fossils