Lecture Notes: The Evolutionary Story of the Human Body
Introduction
The lecture discusses the evolutionary history of human anatomy, from ancient primates to modern humans.
Key aspects of human physiology such as hand structure, color vision, and bipedalism are traced back to ancient ancestors.
The Inner Monkey
Humans share anatomical features with ancient primates.
The coccyx, or tailbone, is a vestige of an ancestral tail.
Modern monkeys, like squirrel monkeys, display physical similarities that connect us to our primate past.
Evolution of Hands
Notharctus, a 50-million-year-old primate, provides insight into early primate anatomy.
Early primate hands had long fingers and nails rather than claws, allowing for better grasping needed in arboreal environments.
Evolution of Color Vision
Early primates initially saw limited colors but evolved to see a broader spectrum, aiding in survival by identifying ripe fruits and nutritious leaves.
The evolution of color vision involved the duplication and mutation of opsin genes.
Research shows that simple genetic changes can significantly impact color perception.
The Trade-off: Vision vs. Smell
Enhanced vision came at the cost of a reduced sense of smell.
Humans have 600 non-functional olfactory genes, indicating a decreased reliance on smell as vision became predominant.
Bipedalism: Walking on Two Legs
Bipedalism is unique among primates and led to significant anatomical changes.
Lucy, a 3.2-million-year-old fossil, shows early developments of bipedalism.
Ardipithecus was another early biped living in woodlands, challenging the theory that bipedalism developed due to savanna environments.
Consequences of Bipedalism
Human skeletons, particularly the spine, reflect the challenges of bipedalism.
The S-shaped curve of the spine is unique and often problematic, causing back issues.
Tool Use and Brain Evolution
The freeing of hands led to tool use, indicative of cognitive development.
Human brains, sharing architecture with primate brains, are highly interconnected, facilitating complex tasks.
The extended human childhood allows for prolonged brain development and learning.
Deep Ancestry
Human brain architecture can be traced back to fish, showing fundamental similarities in structure (forebrain, midbrain, hindbrain).
The genetic roots of brain development predate fish, seen in simple creatures like Amphioxus.
Conclusion
Our bodies contain a record of our evolutionary past, connecting us deeply with all life on Earth.
Understanding our evolutionary history helps us appreciate the intricate design and function of the human body today.