Comment: 21:48 - 23:23 (01:35)
Source: Annenberg/CPB Resources - Earth Revealed - 11. Evolution Through Time
Keywords: "Jamie Webb", fossil, "Rancho La Brea", Cenozoic, life, horse, evolution, ecosystem, woodland, grassland, environment, habitat, "Charles Darwin"
Our transcription: The fossils at Rancho La Brea represent a very brief span of late Cenozoic time, just 25 to 30,000 years.
Though few ancient life localities are as rich as Rancho La Brea, other Cenozoic fossils provide spectacular evidence of evolution spanning millions of years.
The case of the horse is especially stunning.
Appearing near the beginning of the Cenozoic the first horses were no larger than dogs and had four toes on each foot.
They lived in woodlands.
Then, about 40 million years ago a new ecosystem appeared on earth, the grasslands.
Moving in to forage this environment, the horse grew larger, and through time developed hooves to replace toes.
This permitted horses to run swiftly with better chance of survival in the open.
The idea that species gradually changed to better suit their natural habitats was first described by Charles Darwin some 150 years ago.
The main thing that Darwin contributed to our idea of life in the past and what happened was the method of evolution.
Prior to Darwin's idea of evolution, we knew that plants and animals changed.
We knew that they varied over time, but we didn't really have an idea as to why they changed, and Darwin gave us the method.
Geology School Keywords