Evolution of the Human Hand

Introduction

• The story of our hands dates back to ancient creatures using fins to crawl out of the sea (~375 million years ago).
• Ancient mammals evolved fins into paws with short, forward-pointing fingers and claws.

Evolutionary Milestones

Transition from Fins to Hands

• Early mammals like Hyrum had claw-tipped paws.
• A significant evolutionary leap was seen in a tree-dwelling species called Narus.

Narus and Early Primates

• Jonathan Block, a fossil hunter, discovered a nearly complete skeleton of Nartis, a primate from ~50 million years ago.
• Found in Wyoming territory in 1870.
• Narus was a climber and adapted to living in trees.

Features of Narus' Hands

• Hands had long fingers and nails instead of claws.
• Thumb was divergent, allowing opposition with other digits.
• Resembles modern primate hands, marking a turning point in human anatomy.

Evolutionary Advantages

Fine Branch Niche

• Early primate hands evolved to navigate small branches for fruits, flowers, and insects.
• Creatures with short fingers and claws excel on thick branches but struggle at branch ends.
  • Can't grasp thin branches effectively.
• Longer fingers and divergent thumbs allowed for better stability and grasp on fine branches.

Conclusion

• Primate hands adapted for life in trees, crucial for evolution.
• Our hands have a long evolutionary history, originating from adaptations needed in trees.
• The anatomy of our hands allows for complex tasks like writing, typing, and throwing.