Macroevolution and Early Primate Evolution: Origins, Characteristics, and Relationships

1. Chapter 5 Macroevolution and the Early Primates

2. Chapter Outline • What Is Macroevevolution? • When and Where Did the First Primates Appear, and What Were They Like? • When Did the First Monkeys and Apes Appear, and What Were They Like?

3. Macroevolution • Over time, macroevolutionary forces produce new species from old ones. • Macroevolution focuses upon the formation of new species and on the evolutionary relationships between groups of species. • Isolating mechanisms can separate breeding populations and lead to the appearance of new species.

4. Isolating Mechanisms • Geographical • Anatomical structure • Social and cultural concepts

5. Cladogenesis

6. Isolating Mechanisms • In branching evolution, isolating mechanisms separate breeding populations, creating divergent subspecies and then divergent species. • Geographical, biological, or social isolating mechanisms block gene flow between groups, contributing to the accumulation of genetic mutations in each population. • Biological isolating mechanisms include phenomena such as the sterility of hybrid offspring.

7. Anagenesis and Convergence • Anagenesis • When natural selection, over time, favors some variants over others. • Creates a change in a population’s average characteristics. • Convergence • Occurs when two unrelated species come to resemble each other owing to functional similarities.

8. Anagenesis

9. Continental Drift

11. Primate Evolution • Primates arose from a branching of mammalian forms that began more than 100 million years after the appearance of the first mammals. • Most ecological niches that mammals have since occupied were • preempted by reptiles • nonexistent until flowering plants became widespread about 65 million years ago.

13. Ancestral Features • Features in the Eocene genus Adapis are found in prosimians today. Like modern lemurs, it has a postorbital bar, a bony ring around the eye orbit. Note that the orbit is open behind the ring.

14. Primate Evolution • Geological changes in the orientation and position of the earth’s continents affected the global climate. • This played a key role in the evolution and distribution of the primates. • The first primates were arboreal insect eaters and the characteristics of all primates developed as adaptations to this early way of life.

15. Early Primates • The earliest primates developed 60 million years ago in the Paleocene epoch. • They were small arboreal creatures. • Diverse prosimianlike forms were common in the Eocene across what is now North America and Eurasia. • By the late Eocene, 45 million years ago, small primates combining prosimian and anthropoid had emerged.

16. Location of Hominid Fossils

17. Primate Evolution • By the late Eocene small primates combining lemurlike and tarsierlike features with those in monkeys and apes developed. • In the Miocene epoch, apes proliferated and spread over many parts of the Old World. • Ancestors of large apes and humans appeared by 16 m.y.a. and were widespread as recently as 8 m.y.a.

18. Primate Evolution • Details of dentition suggest that hominines arose from these earlier apes. • Some populations lived in parts of Africa where pressures existed to transform a creature just like it into a primitive hominine. • Other populations remained in the forests, developing into today’s bonobo, chimpanzee, and gorilla.