The Human Lineage

1. The Human Lineage The Past in Perspective 4

2. The Human Lineage • Chronicle • Homo Erectus • Hominids Conquer the World • The Age of Ice • Homo Erectus: The Toolmaker • Subsistence • Issues and Debates • Case Study Close-up • Summary

3. Chronicle • Soon after 1.8 million B.P. in Africa and nearly as long ago in Asia and Europe, and acceleration of human evolution took place. • Many paleoanthropologists believe that all of the hominids that follow Homo habilis and predate Homo sapiens—from after 1.8 million B.P until about 300,000 B.P. or even later—belong to a single species: Homo erectus.

4. Chronicle • A recent spate of discoveries has convinced others that this period of human evolution presents us with a number of related, but more or less geographically separate, species. • Homo ergaster in Africa • Homo erectus in central and east Asia • Homo antecessor in Europe.

5. Chronicle Homo Erectus Two competing models for the number of species, evolution, and spread of hominids after 2 million years ago. Figure 4.2 (Old figure 5.2)

6. Homo Erectus • Soon after 1.8 million B.P., a new form of hominid appeared in the fossil record of eastern Africa. • Homo erectus • The cranium of Homo erectus was quite different from that of its evolutionary antecedent, Homo habilis. • The skull was different configured and differently proportioned in ways that signify a shift toward a more human appearance. • The back, or occipital, portion of the erectus skull is rounder that that of habilis, with a much larger area for muscle attachment.

7. Homo Erectus • Soon after 1.8 million B.P. • Homo erectus . . . (continued) • Analysis of cranial endocasts of a number of Homo erectus specimens (Holloway 1980, 1981) shows intriguing similarities to the modern human brain. • Homo erectus crania display a massive ridge of bone called a supraorbital torus, which is present in the skulls of all ape species and is generally absent in the modern human form. • The bones of Homo erectus bear witness to a creature that indisputably walked upright, in a manner similar, if not identical, to that of modern human beings.

8. Homo Erectus • The Evolutionary Position of Homo Erectus • In terms of cranial capacity and morphology, the African erectus fossils reflect a position midway between Homo habilis and anatomically modern human beings.

9. Homo Erectus In this comparison of the skulls of Homo habilis and Homo erectus, the skull of erectus is seen to be larger and more modern (less apelike) than that of habilis. Insert Figure 4.4 (Old figure 5.4)

10. Homo Erectus Fossil localities of Homo erectus. Insert Figure 4.5 (old figure 5.5)

11. Hominids Conquer the World • Fossils very similar to erectus have been found in Asia and date to soon after the appearance of erectus in Africa. • Some of the oldest hominid sites outside of Africa have been found where Africa is connected by land to Southwest Asia and nearby in the southern section of Eurasia. • Researchers recovered crania and tools at Dmasisi near the shore of the Black Sea in the Republic of Georgia in what used to be the Soviet Union. • The tools clearly belong to the Oldowan tradition.

12. Hominids Conquer the World • East Asia • Java is the farthest point in the Old World for Homo erectus populations. • Some of the fossils date to 1.5 million years ago, and at least one cranial fragment was found below the layer that produced the 1.5 million year date (Larick et al. 2001). • China • Stone artifacts associated with Homo erectus were found in the Nihewan Basin of northern China show that they are approximately 1.36 million years old (Zhu et al. 2001).

13. Hominids Conquer the World • Homo erectus: Ocean Explorer? • Stone tools have been found on the Indonesian island of Flores in the western Pacific in a stratigraphic layer dated to as much as 900,000 years ago (Morwood et al. 1998). • If the dates on Flores hold up, Homo erectus had much earlier developed the capacity to make boats or canoes and to navigate and explore far from shore.

14. Hominids Conquer the World • Europe • The oldest unequivocal hominid remains found in western Europe were recovered at the site called Gran Dolina in the Atapuerca Mountains in Spain (Carbonell et al. 1995). • It is reasonable to say that African hominids first entered Europe by at least 800,000 years ago.

15. The Age of Ice • The earth became a significantly colder place, particularly after about 900,000 years ago, with northern latitudes and higher elevations becoming covered by expanding ice fields called glaciers (Shackelton and Opdyke 1973, 1976). • The older period of time is called the Pleistocene epoch. • The Pleistocene was an epoch of fluctuating climate, with periods called glacials much colder than the present. • Within the glacials were colder and warmer periods, with attendant glacial advances (stadials) and retreats (interstadials). • Between the glacials were relatively long interglacial periods, during which the temperature often approached, sometimes equaled, and rarely may even have exceeded the modern level.

16. The Age of Ice • The Oxygen Isotope Curve • The worldwide sequence of glacial advances and retreats can be studied indirectly, via the ratio of two isotopes of oxygen (16O:18O). • The Shackleton and Opdyke curve (1973, 1976) cover the last 780,000 years. • It exhibits 10 periods of drops in 16O and, therefore, significantly colder temperatures and greater ice cover on the earth’s surface. • Adaptive flexibility seems to have been a hallmark of the Homo erectus species.

17. The Age of Ice Worldwide glacial coverage during the peak periods of glaciation in the Pleistocene epoch. Insert Figure 4.9 (Old figure 5.8)

18. The Age of Ice The Shackleton and Opdyke curve of 18O concentration in fossil foraminifera is an indirect reflection of glacial expansion and contraction during the past 780,000 years. Figure 4.10 (Old figure 5.9)

19. Homo Erectus: The Toolmaker • The Acheulean handaxe typifies Homo erectus, at least in Africa and Europe. • The earliest and simplest handaxes have been found in Africa and can be dated to about 1.4 million years ago. • There seems to have been a slow development of the far more complex handaxe form the simpler Oldowan chopper. • Experimental archaeologist Mark Newcomer (1971) determined that at least some were made in three separate steps. • A blank, or preform, was roughed out with a stone hammer into the general shape • The preform was refined via a second stage of percussion with a softer stone or a piece of antler. • The edges were straightened and sharpened with percussion.

20. Subsistence • Hunting, scavenging and gathering wild plants together provided subsistence for Homo habilis. • The Homo erectus diet consisted of much more than meat. • At the 800,000-year-old Gesher Benot Ya’aqov (GBY) in Israel (Goren-Inbar et al. 2002), researchers recovered chunks of stone, and 54 of these chucks exhibited pitting. • Experimental replication indicates that the pits on these stones were produced by using them as hammers to break open nuts.

21. Issues and Debates • Did the Pleistocene Cause the Evolution of Homo Erectus? • Though the first appearance of erectus and the accepted beginning of the Pleistocene epoch are roughly contemporaneous, significant global cooling and the growth of continental ice sheets predate the appearance of erectus as well as its expansion into Asia and Europe.

22. Issues and Debates • What Enabled the Geographic Expansion of Homo Erectus? • Intelligence • Homo erectus seems to have been the first human ancestor to rely on the invented, learned, and passed-down adaptations of culture for survival. • Control of Fire • The best available evidence indicates that Homo erectus was our first ancestor able to control fire.

23. Issues and Debates This graph of the trend in Homo erectus brain size through time show a rather remarkable stability from the first appearance of the species some 1.8 million years ago to the most recent specimens, dating to 400,000 years ago. Insert Figure 4.16 (Old figure 5.15)

24. Issues and Debates • The “Art” of Making Tools • A high level of consistency in handaxe form can be found within sites, as if the makers were adhering to a particular standard. • That such extra care was taken in their production implies that their makers were interested in more than simple utility.

25. Issues and Debates • The Mystery of the Missing Hand Axes • Beginning about 1.4 million years ago, hand axes become ubiquitous at Homo erectus sites in Africa. • Hand axes are extremely rare or more commonly entirely absent from Homo erectus sites in Asia east of the Indian subcontinent. • It seems that Homo erectus populations in Africa expanded into Asia before they had developed Acheulean technology with its emblematic hand axe.

26. Issues and Debates • Raising Homo Erectus • Human children are utterly dependent on adults to satisfy all their needs for a very long time. • The term altricial is used to characterize baby birds who are completely dependent on their parents for fulfilling their needs. • Human babies are said to be secondarily altricial. • An addition hypothesis holds that one of the key changes that characterized ancient hominids from Homo habilis on is neoteny, or the “holding on” to features that are typical of newborn apes (Gould, 1977). • A long period of learning is emblematic of the human species.

27. Issues and Debates • When Did Homo Erectus Become Extinct? • Only the Homo erectus population in Africa is directly ancestral to us. • That line evolved into another hominid that looked and behaved more like modern humans. • Stability or Change? • Homo erectus is one of the longest-lived of the hominid species. • About 400,000 years ago a steep increase in brain size over a short interval is seen. • Those changes produced and defined the first Homo sapiens.

28. Case Study Close-up • In 1918, a fossil locality southwest of Beijing, China, was explored by Swedish geologist Johan Gunnar Andersoon. • The expedition recovered, along with thousands of specimens of ancient animals, 15 fragmentary skulls, 6 more complete crania, 13 fragmentary mandibles, 3 upper jaws, some post cranial bones, and a single vertebra of Peking Man (Jia and Juang 1990:161-62). • The assemblage was lost during World War II when the fossils were being removed from China by U.S. Marines to keep them away from Japanese invaders.

29. Summary • Sometime after 1.8 million years ago, Homo habilis was replaced by a new hominid species, Homo erectus. • Homo erectus was the first ancestral human being to expand beyond the borders of our hominid family’s African birthplace and nursery. • It was intelligence and not any physical adaptation that enabled Homo erectus to adapt to the diversity of habitats offered throughout Asia.