antropology 3/3
Overview of Extinction Events
Element: Rare on Earth's surface but common in meteors, found at impact sites (e.g., KT boundary).
Evidence suggests meteorite impact dispersed elements into the atmosphere, leading to significant extinction events.
Volcanism as an Alternative Hypothesis
Increased volcanic activity may have contributed to climate change post-extinction.
Volcanic eruptions release rock particles into the atmosphere, leading to global effects on climate similar to recent examples (such as the 2010 Iceland eruption).
Mammalian Speciation after the Dinosaurs
After dinosaur extinction, mammals rapidly speciate into available ecological niches.
The Paleocene epoch witnesses an evolutionary radiation of mammals, filling niches left by the dinosaurs.
Orders of mammals emerge, including primates, carnivores, and bats.
Paleocene Epoch (66-65 million years ago)
Characterized by dinosaur extinction and mammalian diversification.
Early mammals include ancestors of tree shrews and dermopterans.
Plesiadapiformes, a group similar to primates, evolve but lack defining primate features.
Early mammals don't exhibit traits typical of modern primates, such as grasping hands or forward-facing eyes.
Modern Primate Characteristics
Grasping hands and feet, presence of nails instead of claws, and optical convergence (overlapping left and right fields of vision).
Relative brain size to body size is larger compared to other mammals.
Majority of modern primates are arboreal.
Evidence in the Fossil Record
First evidence of traits associated with modern primates appears later in the Eocene epoch (55 to 35 million years ago).
Two main groups of early primates: adapoids and omomyoids.
The fossil record shows characteristics defining modern primates: large brain size, forward-facing eye orbits, and grasping feet.
Eocene Environmental Context
Supported growth of forests; primates thrived in warm, wet conditions.
Intermittent connections existed between continents as sea levels rose and fell.
Fossils show early primates characterized by adaptations for arboreal life.
Oligocene Epoch (35-24 million years ago)
Cooler climates led to forest decline and adaptations of primates.
Emergence of first monkeys and New World monkeys due to environmental changes.
Circumpolar current establishment drastically impacts global temperatures; polar ice caps begin forming.
Evolutionary Impacts During the Oligocene
As temperatures drop, habitats contract leading to primate extinctions in North America.
Fossil records indicate the arrival of early catarrhines (ancestors of modern old-world monkeys and apes).
Migration and Rafting Hypothesis
New World monkeys likely derived from African primates through rafting events.
Evidence of land separation and support for the migration of species over time.
Miocene Epoch (24-5 million years ago)
First appearance of apes and the tribe hominini (ancestors of humans) by the end of the epoch.
Patterns of cooling and drying dramatically affect primate habitats.
Expansion of forests early in the Miocene followed by a decline due to climate changes.
Ape Evolution and Ecological Changes
Beginning of Miocene exhibited warmer, wetter environments conducive to early ape development.
Apes adapt more specialized traits suited for arboreal lifestyles.
Diversity of species decreases in favor of monkeys due to environmental pressures that dryer conditions bring.
Climatic Events and Evolutionary Divergence
Climate change, including monsoonal patterns from the collision of India and Asia, shifts ecological environments.
The Continental shifts contribute to significant changes in biodiversity, impacting primate evolution.
Final Miocene climatic changes coincide with primate evolutionary divergence, notably between human ancestors and chimpanzees.
Summary of Evolutionary Changes (60 million years)
Transition from Cretaceous conditions (warm, wet) to drastic climate changes favoring mammalian evolution.
Emphasizes the relationships between environmental changes and mammalian adaptations over time, leading up to modern primate profiles.