🦕Intro to Paleoanthropology Unit 12 – Paleoanthropology: Species & Evolution

Key Concepts & Definitions

• Paleoanthropology studies the origins and development of early humans and their ancestors through fossil evidence, archaeological remains, and comparative studies of living primates
• Hominins include modern humans and extinct species more closely related to humans than chimpanzees, characterized by bipedalism and larger brains
• Australopithecines early hominins that lived in Africa between 4.2 and 1.4 million years ago, with a mix of ape-like and human-like features
  • Includes species like Australopithecus afarensis (Lucy) and Australopithecus africanus
• Homo genus that includes modern humans (Homo sapiens) and closely related extinct species like Homo erectus and Homo neanderthalensis
• Bipedalism walking upright on two legs, a key adaptation in human evolution that freed the hands for tool use and allowed for long-distance travel
• Encephalization increase in brain size relative to body size over the course of human evolution, associated with cognitive development and cultural complexity
• Stone tools earliest evidence of human technology, with the Oldowan industry dating back to 2.6 million years ago in Africa
• Mitochondrial Eve hypothetical most recent common ancestor of all living humans, traced through mitochondrial DNA inherited from the mother

Timeline of Human Evolution

• 7-6 million years ago (mya) divergence of the human lineage from the common ancestor with chimpanzees
• 4.2-3.9 mya Australopithecus anamensis, one of the earliest known hominins, lived in East Africa
• 3.7-3.0 mya Australopithecus afarensis (Lucy) lived in East Africa, with evidence of bipedalism and a mix of ape-like and human-like features
• 2.8-1.4 mya Homo habilis, the earliest member of the genus Homo, appeared in Africa with a larger brain and more advanced stone tools (Oldowan industry)
• 1.9-0.3 mya Homo erectus, the first hominin to leave Africa and spread across Asia and Europe, with a larger brain, more complex tools (Acheulean industry), and evidence of fire use
  • Includes the Peking Man and Java Man fossils
• 600,000-30,000 years ago Homo neanderthalensis (Neanderthals) lived in Europe and Western Asia, with a stocky build, large brain, and complex tools and cultural practices
• 300,000-present Homo sapiens, modern humans, emerged in Africa and spread across the world, with advanced cognitive abilities, language, and cultural complexity

Major Hominid Species

• Sahelanthropus tchadensis (7-6 mya) earliest known potential hominin, with evidence of bipedalism but a small brain, found in Chad
• Orrorin tugenensis (6 mya) early hominin with evidence of bipedalism, found in Kenya
• Ardipithecus ramidus (4.4 mya) early hominin with a mix of ape-like and human-like features, found in Ethiopia
• Australopithecus afarensis (3.7-3.0 mya) well-known early hominin with evidence of bipedalism, including the famous Lucy fossil, found in Ethiopia
• Australopithecus africanus (3.3-2.1 mya) gracile australopithecine with a larger brain and more human-like teeth, found in South Africa
• Paranthropus robustus (2.0-1.2 mya) robust australopithecine with large teeth and a strong jaw, adapted to a tough, plant-based diet, found in South Africa
• Homo habilis (2.8-1.4 mya) earliest member of the genus Homo, with a larger brain and more advanced stone tools (Oldowan industry), found in Africa
• Homo erectus (1.9-0.3 mya) first hominin to leave Africa, with a larger brain, more complex tools (Acheulean industry), and evidence of fire use, found across Africa, Asia, and Europe

Fossil Evidence & Discoveries

• Lucy (Australopithecus afarensis) a 3.2 million-year-old partial skeleton found in Ethiopia in 1974, providing evidence of bipedalism and a mix of ape-like and human-like features
• Laetoli footprints a 3.6 million-year-old trail of fossilized footprints in Tanzania, providing clear evidence of bipedalism in early hominins
• Turkana Boy (Homo erectus) a 1.6 million-year-old nearly complete skeleton of a young male found in Kenya, providing insights into the anatomy and growth of Homo erectus
• Peking Man (Homo erectus) a collection of fossil remains found in a cave near Beijing, China, dating to around 750,000 years ago, providing evidence of Homo erectus in Asia
• Neanderthal fossils numerous fossil remains of Homo neanderthalensis found across Europe and Western Asia, providing insights into their anatomy, behavior, and genetic relationship to modern humans
  • Includes the Shanidar Cave burials in Iraq, which suggest complex social and cultural practices
• Denisovan fossils a few fossil fragments and teeth found in Siberia and Tibet, belonging to a previously unknown hominin group related to Neanderthals, identified through genetic analysis
• Homo naledi a recently discovered species found in the Rising Star Cave system in South Africa, with a mix of primitive and advanced features, dating to around 300,000 years ago
• Jebel Irhoud fossils a collection of Homo sapiens fossils found in Morocco, dating to around 300,000 years ago, pushing back the origins of our species in Africa

Evolutionary Adaptations

• Bipedalism walking upright on two legs, allowing for more efficient long-distance travel, freeing the hands for tool use and carrying, and changes in pelvic structure
• Encephalization increase in brain size relative to body size, associated with cognitive development, language, and cultural complexity
  • Homo erectus had a brain size of around 900 cc, while modern humans have an average brain size of 1,300 cc
• Reduced dentition and jaw size as diet shifted towards more meat and cooked food, requiring less chewing and biting force
• Increased manual dexterity and precision grip associated with tool use and manipulation, enabled by changes in hand and wrist anatomy
• Changes in life history longer childhoods, extended periods of learning and cultural transmission, and increased longevity compared to other primates
• Adaptations to diverse environments as hominins spread across Africa, Asia, and Europe, they adapted to various climates and ecosystems through biological and cultural means
  • Neanderthals had a stocky build and large nose, possibly adapted to cold climates
• Development of language and symbolic thought associated with increased brain size and cultural complexity, allowing for more efficient communication and abstract reasoning
• Shifts in social structure and behavior including increased cooperation, division of labor, and cultural practices like tool-making, fire use, and burial of the dead

Research Methods in Paleoanthropology

• Fossil analysis studying the morphology, age, and context of hominin fossil remains to understand their anatomy, evolutionary relationships, and behavior
  • Includes techniques like radiometric dating, CT scanning, and microscopic analysis
• Comparative anatomy comparing the anatomy of extinct hominins to modern humans and other primates to identify shared and derived traits, and to reconstruct their behavior and ecology
• Archaeology studying the material culture and environmental context of hominin sites to understand their behavior, diet, and cultural practices
  • Includes analyzing stone tools, animal bones, and plant remains
• Paleoenvironmental reconstruction using geological, botanical, and faunal evidence to reconstruct the climate, landscape, and ecosystem in which hominins lived
  • Includes analyzing pollen, soil samples, and stable isotopes
• Genetic analysis studying the DNA of extinct hominins (when preserved) and comparing it to modern human populations to understand their evolutionary relationships and admixture
  • Includes ancient DNA extraction and sequencing, and population genetics
• Experimental archaeology replicating ancient technologies and behaviors to understand how they were made and used, and to test hypotheses about hominin capabilities
  • Includes making and using stone tools, building shelters, and processing food
• Ethnoarchaeology studying the material culture and behavior of modern hunter-gatherer and traditional societies to provide analogies for interpreting the archaeological record
• Taphonomy studying the processes that affect the preservation and modification of fossil remains and archaeological sites, to understand biases and limitations in the record

Controversies & Debates

• Phylogenetic relationships and taxonomy debates over the evolutionary relationships among hominin species, and how they should be classified and named
  • Includes the placement of Homo habilis and Homo rudolfensis, and the relationship between Homo sapiens and Neanderthals
• Bipedalism and its origins disagreements over the timing, context, and selective pressures that led to the evolution of bipedalism in the hominin lineage
  • Includes the role of climate change, habitat shifts, and social behavior
• The "hobbit" (Homo floresiensis) debates over whether the small-bodied hominin remains found on the Indonesian island of Flores represent a distinct species or a pathological modern human population
• Neanderthal behavior and cognition disagreements over the cognitive abilities, language, and cultural complexity of Neanderthals, and how they compared to modern humans
  • Includes debates over their use of symbolism, burial practices, and technological innovations
• The "Out of Africa" model and multiregional hypothesis competing models for the origin and dispersal of Homo sapiens, with the "Out of Africa" model proposing a single African origin and the multiregional hypothesis suggesting regional continuity and gene flow
• The role of climate change in human evolution debates over how changes in climate and environment, such as the shift to drier and more open habitats in Africa, influenced the evolution and dispersal of hominins
• The "Paleolithic diet" and its relevance disagreements over the composition and health implications of the diet of Paleolithic hunter-gatherers, and its applicability to modern human nutrition
• Ethics and repatriation of human remains debates over the ethical handling, study, and repatriation of hominin fossil remains, particularly those of indigenous peoples and historically marginalized groups

Implications for Understanding Human Origins

• Demonstrating the long and complex history of human evolution, with multiple species and lineages, rather than a simple linear progression
• Highlighting the importance of Africa as the birthplace of humanity, with the earliest hominins and the origins of Homo sapiens on the continent
• Revealing the diversity and adaptability of hominins, as they spread across the world and adapted to various environments through biological and cultural means
• Emphasizing the role of bipedalism, tool use, and brain size increase as key adaptations in human evolution, enabling new behaviors and ecological niches
• Illustrating the complex relationships and interactions between hominin species, including coexistence, competition, and admixture (interbreeding)
  • Genetic evidence shows that modern humans interbred with Neanderthals and Denisovans, leaving traces in our DNA
• Providing insights into the behavior and cultural practices of extinct hominins, from the earliest stone tools to the burial practices and symbolism of Neanderthals
• Raising questions about the definition and uniqueness of Homo sapiens, as we discover more about the capabilities and diversity of other hominin species
• Informing our understanding of modern human diversity, as the global dispersal and adaptation of Homo sapiens shaped the genetic and phenotypic variation we see today
• Highlighting the importance of interdisciplinary research, combining evidence from fossils, archaeology, genetics, and other fields to build a comprehensive picture of human origins
• Encouraging a greater appreciation for the deep history and common ancestry of all humans, promoting a shared sense of identity and connection across cultures and populations