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Evolutionary Principles: Human Classification and Key Challenges to Early Beliefs

This chapter explores the classification of humans within the Animalia kingdom, tracing our lineage from Kingdom Animalia down to Homo sapiens. It discusses significant challenges to early beliefs through biogeography, comparative morphology, and the fossil record. Introduction to Darwin's theory of evolution by natural selection highlights population variation and mutation's role in evolution. The chapter also examines genetic drift, speciation, adaptive radiation, and trends in human evolution — from skeletal organization to changes in behavior. Insights from comparative biochemistry provide additional evidence for our evolutionary journey.

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Evolutionary Principles: Human Classification and Key Challenges to Early Beliefs

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  1. Principles of Evolution Chapter 24

  2. Classification of Humans • Kingdom Animalia • Phylum Chordata • Class Mammalia • Order Primates • Family Hominidae • Genus Homo • Species sapiens

  3. Challenges to Early Beliefs • Biogeography - discovery of species in isolated locales • Comparative morphology - similarities between animals, parts with no functions • Fossils - deep layers with simple fossils, overlying layers with increasing complexity

  4. Charles Darwin • Proposed the theory of evolution by way of natural selection • Influenced by • Observations made while naturalist on H.M.S. Beagle • Conversations with other naturalists • Writings of Thomas Malthus

  5. Variation in Populations • Individuals do not evolve; populations do • Members of a population have similar traits • Details of traits vary among individuals • Some variation results from genetic differences (different alleles)

  6. Mutation • A heritable change in DNA • Most are harmful • Some are neutral • A few are beneficial

  7. Natural Selection • Individuals vary • Some variations are heritable • Some versions of traits increase fitness • Natural selection is the difference in survival and reproduction in individuals who have different versions of a trait

  8. Evolving Populations • A population is evolving when some forms of a trait are becoming more or less common relative to the other forms • Over time, shifts in the makeup of gene pools have been responsible for the amazing diversity of life forms on Earth

  9. Other Changes to Gene Pool • Genetic drift • Founder effect • Virtually no Native Americans with type B blood • Gene flow • Physical movement of alleles • Helps keep neighboring populations genetically similar

  10. Species • A genetic unit consisting of one or more populations of organisms • Members can interbreed and produce fertile offspring under natural conditions • Reproductively isolated from other species

  11. Speciation time A time B time C time D time

  12. Fossils • Usually hard parts • Form in sedimentary rock • Stratification • Fossil record is biased

  13. Biogeography Distribution of plants and animals Plate tectonics

  14. Comparative Morphology • Homology • Similarity in body parts in different organisms • Attributable to descent from a common ancestor • Analogy • Similarity in body parts in different organisms • Attributable to similar environmental pressures

  15. Homologous Structures Vertebrate forelimbs

  16. Comparative Embryology • Early vertebrate embryos strongly resemble one another • Same plan of development Fish Reptile Bird Mammal

  17. Proportional Skull Changes Chimpanzee Human

  18. Evidence from Comparative Biochemistry • Molecular clocks • Neutral mutations • Protein comparisons • Cytochrome C • Nucleic-acid comparisons • Base-pairing of DNA or RNA from one species to another

  19. Extinctions - End of the Line • Background extinction • Local changing conditions • Mass extinction • Catastrophic global event • 65 million years ago • Probably asteroid impact

  20. Adaptive Radiation • New species of a lineage moves into a wide range of habitats • Has occurred in the human lineage • Homo habilis remained in Africa • H. erectus went to Europe, Asia • H. sapiens evolved by 100,000 years ago

  21. Trends in Human Evolution • Upright walking • Refined hand movements • Enhanced daytime vision • Changes in dentition • Changes in brain and behavior

  22. Comparison of Skeletal Organization

  23. Trend toward Longer Life Spans and Dependency

  24. From Primates to Hominids • 60 million years ago • Tropical forests • Small rodents, tree shrews • 54 - 38 million years ago • Primates in trees • 36 million years ago • Tree-dwelling anthropoids • 10 - 5 million years ago • First hominoids

  25. Early Earth • Primitive atmosphere • H2 • N2 • CO • CO2 • Probably no O2

  26. Complex Compounds Form Organic compounds may have: • Formed when lightning interacted with gases in early atmosphere • Assembled on clays in tidal flats • Formed near hydrothermal vents

  27. Emergence of First Living Cells • Self-Replicating Systems • RNA • DNA • Plasma Membranes • Proto-cells

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