Hominin Relations
This unit will explore recent developments and current thinking about how early hominins were evolutionarily related to one another. This subject phylogeny has always attracted the attention of anthropologists, often overshadowing the more basic questions of hominin biology, such as subsistence strategies and behavior. During the first half of the twentieth century, scholars commonly assigned a new species name to virtually each new fossil unearthed. In this splitting paradigm, each variant in...
KEY QUESTIONS Noa
Why did Uniformitarianism become so powerful a force in late- nineteenth- and twentieth-century scientific thinking How might mass extinction be explained as a consequence of How does mass extinction influence the history of life How can the hypothesis of asteroid impact be tested and mass extinction. Biotic crises are not simply background extinctions writ large. This idea makes sense because, in the history of life, many successful species or groups of species have met abrupt ends in mass...
KEY REFERENCES Bee
Br uer G, Mbua E. Homo erectus features used in cladistics and their variability in Asian and African hominids. J Human Evol 1992 22 79-108. Brown FH, et al. Early Homo erectus skeleton from west Lake Turkana, Kenya. Nature 1985 316 788-792. Dean C, et al. Growth patterns in teeth distinguish modern humans from Homo erectus and earlier hominins. Nature 2001 414 628-631. Gabunia L, et al. Earliest Pleistocene hominid cranial remains from Dmanisi, Republic of Georgia. Science 2000 288 1019-1025....
Mass Extinctions Are Qualitatively Different
The University of Chicago paleontologist David Jablonski has investigated the nature of that selection by comparing the pattern in background and mass extinction periods. During background extinction, several factors contribute to the protection of a species from extinction. Species that are geographically widespread resist extinction, for instance. Likewise, marine species that send their larvae far and wide drifting with the currents resist extinction, for similar reasons. A group of related...
EanY hypotheses and recem developments
During the 1960s and early 1970s, paleoanthropologists considered hunting to be the primary human adaptation, a notion that has deep intellectual roots, reaching back as far as Darwin's Descent of Man. The apogee of the hunting hypothesis was marked by a Wenner-Gren Foundation conference in Chicago in 1966, titled Man the Hunter. The conference not only stressed the idyllic nature of the hunter-gatherer existence the first affluent society as one authority termed it but also firmly identified...
The Earliest Hominoids
Hominoid fossils are known throughout much of the Miocene in Africa and Eurasia, with the earliest specimens of a species FIGURE 16.2 Proconsul africanus This reconstruction is based on fossils found prior to 1959 colored by Mary Leakey and in 1980, among the Nairobi Museum collections, by Alan Walker and Martin Pickford. This individual, a young female that lived approximately 18 million years ago, has characteristics of both modern monkeys in its long trunk and arm and hand bones and modern...
The function of AcheuLean handaxes
The function of Acheulean handaxes has long been a subject of speculation. A particularly unlikely explanation is that they were used as lethal projectiles, thrown like discuses as a means of killing prey. More prosaic suggestions hypothesize that they were used as axes or heavy-duty knives. In experimental studies, Indiana University archeologist Nicholas Toth found that handaxes and cleavers were highly effective at slicing tough hide, such as that of elephants. The combination of weight and...
EneRGetics of bipedansm possle impucation in its origin
A more parsimonious and therefore more scientifically attractive explanation of bipedalism was proposed by Peter Rodman and Henry McHenry of the University of California at Davis in a 1980 publication. Very simply, they suggest that bipedalism might have evolved, not as part of a change in the nature of the diet or social structure, but merely as a result of a change in the distribution of existing dietary resources. Specifically, in the more open habitats of the late Miocene, hominoid dietary...
NEandERthaL anatomy
Neanderthal anatomy represents a mixture of primitive characters, derived characters that are shared with other hominins, and derived characters that are unique to Neanderthals see figure 27.1 . In general terms, Neanderthals b. Well-developed supraorbital torus c. Large face, broad nasal opening a. Lateral reduction of brow ridge a. Spherical shape of cranial vault seen in rear view b. Midfacial projection, large nose ficure 27.2 Skull shape The triangle in the Neanderthal skull left shows the...
Technologies
About half a million years after the first appearance of Homo ergaster, a new form of stone-tool technology is seen in the archeo-logical record. Known as the Acheulean, the assemblage is characterized by large forms, particularly the handaxe, which required greater skill in conceptualization and manufacture. They would have allowed more extensive manipulation of animal resources. The Acheulean is seen first in Africa, and later in Eurasia, but not in East Asia. It remained relatively unchanged...
Molecular Studies
The term molecular anthropology was coined in 1962 by Emile Zuckerkandl, who, with Linus Pauling, invented the notion of using molecular evidence to uncover evolutionary histories see unit 8 . At the time, Zuckerkandl had already discerned a hint of what was to unfold in the science when he compared enzymic digests of proteins from humans, gorillas, chimpanzees, and orangutans. As mentioned earlier FICURE 15.3 Palate and tooth anatomy In apes, the jaw is U-shaped in modern humans and later...
Same Story Different Sequences
Traditionally, paleoanthropologists have recognized four key events in human evolution the origin of terrestriality coming to the ground from the trees , bipedality upright walking , encephalization brain expansion in relation to body size , and culture or civilization . While these four events have usually featured in accounts of human origins, paleoanthropologists have disagreed about the order in which they were thought to have occurred. See figure 2.1. For instance, Henry Fairfield Osborn,...
Origin Of Bipedalism
Upright walking bipedalism is the adaptation that defines hominins, and preceded the origin of tool use and enlarged brains by at least 2 million years. Many hypotheses have been put forward to explain the adaptive path that led to this mode of locomotion, including improved energetics and efficiency of posture for harvesting food resources. Although Homo sapiens is not the only primate to walk on two feet for instance, chimpanzees, a small species of orangutan, and gibbons often use this form...
Extinction And Patterns Of Evolution
Mass extinctions have come to be recognized as qualitatively different from background extinction, which is probably driven by natural selection. During biotic crises, species become extinct for reasons other than their adaptation to their environment. Mass extinctions shape the history of life, principally through the nature of the species that survive through them. Life first evolved on Earth almost 4 billion years ago, in the form of simple, single-celled organisms. Not until half a billion...
Climate Change And Habitat Theory
A considerable body of data has been amassed during the past decade relating to the Earth's climate during the Cenozoic, from 65 million years ago to the present, and par- Three pacemakers of the Milankovitch climate cycles Three pacemakers of the Milankovitch climate cycles 800 900 I000 Summer sunshine cal cm2 day 800 900 I000 Summer sunshine cal cm2 day FICURE 5.3 Milankovitch climate cycles of the past 600,000 years Superimposed on long-term global climate change are regular cycles driven by...
KEY REFERENCES Aab
Aiello LC. Allometry and the analysis of size and shape in human evolution. J Human Evol 1992 22 127-147. Hartwig-Scherer S, Martin RD. Was Lucy more human than her child J Human Evol 1991 21 439-449. Hill A, et al. Earliest Homo. Nature 1992 355 719-722. Johanson DC, et al. New partial skeleton of Homo habilis from Olduvai Gorge, Tanzania. Nature 1987 327 205-209. Lieberman DE, et al. Homoplasy and early Homo an analysis of the evolutionary relationships of H. habilis sensu stricto and H....
Bodies Size And Shape
The evolution of body size and shape is influenced by many factors, including prevailing climate reflecting body heat production and dissipation and lifestyle activities reflecting strength required for subsistence . Through human prehistory, bodies generally became more robust, exemplified by the Neanderthals. Homo sapiens individuals were less robust and taller than Neanderthals when they arose. It is striking that human populations in different parts of the world vary significantly in their...
The Influence Of Catastrophism
In his Origin of Species, Darwin essentially denied the fact of mass extinction, stating that extinction is a slow, steady process, with no occasional surges in rate. He also argued that species become extinct because they prove adaptively inferior to their competitors. Darwin's equation of extinction with adaptive inferiority clearly derives from his theory of natural selection, and it powerfully shaped biologists' thinking. The fact of extinction had been demonstrated before Darwin's time, by...
KEY REFERENCES Mjg
Andrews P. Ecological apes and ancestors. Nature 1995 376 555-556. Asfaw B, et al. Australopithecus garhi a new species of early hominid from Ethiopia. Science 1999 284 629-635. Brunet M, et al. A new hominid from the Upper Miocene of Chad, Central Africa. Nature 2002 418 145-151. Collard M, Wood B. How reliable are human phylogenetic hypotheses Proc Natl Acad Sci USA 2000 97 5003-5006. Dart R. Adventures with the missing link. New York Viking Press, 1959. Johanson DC, White TD. A systematic...
Schick K.d And N. Toth
Gibbons A. Tracing the identity of the first tool makers. Science 1997 276 32. Gibson KR, Ingold T, eds. Tools, language and cognition in human evolution. Cambridge, UK Cambridge University Press, 1993. Keeley LH, Toth N. Microwear polishes on early tools from Koobi Fora, Kenya. Nature 1981 293 464-465. Panger MA, et al. Older than the Oldowan Rethinking the emergence of hominin tool use. Evol Anthropol 2002 11 235-245. Schick KD, Toth N. Making silent stones speak. New York Simon and Schuster,...
Olduvai Stone Tools
reasons related to the history of the science of archeology and the impact of new discoveries, the classification of the different periods and stages of cultural development in sub-Saharan Africa and Eurasia represents an uneven mixture of cultural innovation and chronology. See text for details. Bearing in mind the elasticity of stage boundaries, technology development unfolded as follows. The beginning of the ESA corresponds with the first appearance of mode I tools, 2.6 million years ago the...
Basic anatomy
Perhaps the most obvious trend in the structure of the primate jaw and face throughout evolution is its shortening from front to back and its deepening from top to bottom, going from the pointed snout of lemurs to the flat face of Homo sapiens. Structurally, this change involved the progressive tucking of the jaws under the brain case, which steadily reduced the angle of the lower jaw bone mandible until it reached the virtual L shape seen in humans. See figures 18.1 and 18.2. Functionally, the...
KEY REFERENCES Jhe
Aitken MJ, Valladas H. Luminescence dating relevant to human origins. Phil Trans Roy Soc B 1992 337 139-148. Brown FH, et al. An integrated Plio-Pleistocene chronology for the Turkana Basin. In Delson E, ed. Ancestors the hard evidence. New York Alan R Liss, 1985 82-90. Chen Y, et al. The edge of time dating young volcanic ash layers with the argon-40 argon-39 laser probe. Science 1996 274 1176-1178. Deino A, et al. Argon-40 argon-39 dating in paleoanthropology and archeology. Evol Anthropol...
MorphoLogicaL interpretations
Since the time of Darwin and Huxley, anthropologists have recognized that humans' closest relatives are the African great apes, the chimpanzee and gorilla, with the Asian great ape, the orangutan, more distant. This conclusion is based principally on comparative anatomy of the hominoids. For a long time the question of the evolutionary relationship between humans, chimpanzees, and gorillas was debated. It seems now to have been resolved, principally based on molecular evidence. For instance,...
Background To Human Evolution
8 Systematics Morphological and Molecular Paleoanthropologists have a suite of techniques available to them for inferring the age of fossils and artifacts. Typically, the techniques depend on determining the age of material associated with the relics in question, such as the strata in which they are found or other fossils of known age. Many of the techniques are based on the decay of radioactive isotopes. An accurate time scale is a crucial aspect of reconstructing the pattern of evolution of...
KEY REFERENCES Gic
Broecker WS, Denton GH. What drives glacial cycles Sci Am Jan 1990 48-56. Carson HL. The processes whereby species originate. BioScience 1987 37 715-720. deMenocal PB. Plio-Pleistocene African climate. Science 1995 270 53-59. Foley RA. Speciation, extinction and climate change in hominid evolution. J Human Evol 1994 26 275-289. The evolutionary geography of Pliocene hominids. In Bromate T, Schrenk F, eds. African biogeography, climate change, and hominid evolution. Oxford Oxford University...
Principles of cumatic adaptation in human populations
Despite the long pedigree of Bergmann's and Allen's ecogeo-graphical rules, anthropologists were slow to apply them to human variation. Interest in this relationship emerged in the 1950s and 1960s, when climate began to be recognized as an important influence in determining anatomical differences among different geographical populations. For instance, the bodily differences between the tall, thin Nilotics at the equator and the short, bulky Eskimos in the Arctic came to be viewed as a direct...
KEY REFERENCES Bot
Di Fiore A, Rendall D. Evolution of social organization. Proc Natl Acad Sci USA 1994 91 9941-9945. Dunbar RIM, Barrett L. Cousins our primate relatives. New York Dorling Kindersley, 2000. Fleagle JG. Primate adaptation and evolution. New York Academic Press, 1999, 2nd ed. Foley RA. Evolution and adaptive significance of hominid maternal behavior. In Price CR, et al. Motherhood in human and nonhuman primates. Basel Karger, 1994 27-36. Foley RA. Humans before humanity. Oxford Blackwell, 1997....
NatuRE of thE hominin ancEstoR
Fossil evidence of the common ancestor of African apes and humans has yet to be found, not least because the hominoid fossil record in Africa between 4.5 and 8 million years is still sparse. One question is, How would such a creature be recognized Ancestral anatomy can be inferred, based on comparisons among living and extinct hominoids. As a result, the common ancestor is now widely believed to have been intermediate in size between the gibbon and the chimpanzee it is imagined to have been...
The Changing Position Of Homo Erectus
Homo erectus was long assumed to be the species intermediate between early Homo and Homo sapiens. Now, however, many scholars believe that the specimens assigned to Homo erectus in fact represent two species, Homo erectus and Homo ergaster, with ergaster being the precursor of erectus. Whatever the true interpretation, it is clear that the emergence of erectus ergaster represented a new grade of hominin, with a very different behavioral repertoire that included the ability to expand its range...
The earuest known homo
The strongest claims for evidence of Homo earlier than 2 million years come from the recent reassessment of a cranial fragment from Kenya and a recently discovered mandible from the site of Uraha in Malawi, which lies between East Africa and South Africa. In 1967, the temporal bone side of the head of a hominin was discovered in the Chemeron formation near Lake Baringo, in central Kenya. The structure around the ear-specifically the mandibular fossa, or jaw joint is diagnostic of Homo. The...
Absolute Dating Techniques Thermoluminescence And Electron Spin Resonance
Two relatively new dating techniques depend on the principle that electrons in certain minerals become excited to higher energy levels when irradiated by radioisotopes of uranium, thorium, and potassium, which occur naturally in the ground and in cosmic rays. The radioactive rays knock off the negatively charged electrons from atoms, leaving positively charged holes. These electrons diffuse through the crystal lattice and usually recombine with other holes, returning to the ground state. But...
KEY REFERENCES Iaa
Blackwell LR, D'Errico F. From the cover evidence of termite foraging by Swartkrans early hominids. Proc Natl Acad Sci USA 2001 98 1358-1363. Clarke RJ, Tobias PV. Sterkfontein member 2 foot bones of the oldest South African hominid. Science 1995 269 521-524. Conroy GC, et al. Endocranial capacity in an early hominid cranium from Sterkfontein, South Africa. Science 1998 280 1730-1731. Crompton RH, et al. The mechanical effectiveness of erect and bent-hip, bent knee bipedal walking in...
Anatomy and bioLogy of eany homo
As previously noted, the brain capacity of early Homo is larger than that of the australopithecines, a change that produces several associated anatomical characteristics. For instance, the temple areas in australopithecines narrow markedly best seen from top view , forming what is known as the postorbital constriction. In early Homo, this constriction is much reduced because of the expanded brain. In addition, the face of an australopithecine is large relative to the size of its cranial vault,...
Relative Dating Techniques
Relative dating techniques include faunal correlation and paleomagnetism. Geologists and paleontologists have long used fossils to structure prehistory. For instance, the geological time scale for the history of life on Earth is built upon major changes in fossil populations, such as appearances and disappearances of groups. Because they are interested in a finer-scale approach, archeologists and anthropologists often look for evolutionary changes within groups. Among the most important species...
a brief history of discovery
The first discoveries of Homo erectus were made in 1891 and 1892 in Java, Indonesia, by Eugene Dubois, a Dutch medical doctor, who had gone there specifically to search for the missing link. The specimens were of a skull cap and a complete thigh bone, or femur, which indicated that the creature had walked upright. Although he was initially ambivalent over the human nature of his fossil find, Dubois eventually came to name the species Pithecanthropus erectus, or upright ape man, inspired in part...
Australopithecines
The abundance of fossil remains of australopithecine species, particularly of afarensis, africanus, and boisei robustus, allows insight into how these creatures lived that is not possible for other pre-Homo hominins. Australopithecines were apelike from the neck up and humanlike from the neck down. Though apelike in parts of the cra-mum, the australopithecine face does not protrude as much as in apes, and the cheek teeth are large and flat, while the anterior teeth were relatively smaller,...
Absolute Dating Techniques Radiopotassium Dating
The majority of absolute dating methods are radiometric, which depends on radioactive change in certain minerals. All methods share the same two principles. First, some action Volcanic ash contains potassium-rich minerals, such as feldspar. A small percentage of the potassium exists as a radioisotope, potassium-40, which has argon-40 as one of its decay products. In the laboratory, crystals of feldspar are irradiated with neutrons, which converts the stable potassium-39 isotope to argon-39. The...