Big History: The Big Bang, Life on Earth, and the Rise of Humanity

Lecture 14: The Evidence for Natural Selection

there are occasional errors, which create the tiny variations that provide the

raw material on which natural selection works.

Darwin feared that we could never observe natural selection directly because

it was such a gradual process. In the 20th century, work on rapidly reproducing

species such as fruit À ies (Drosophila) has allowed us to observe evolution

at work in great detail. The rapid evolution of disease vectors such as AIDS

also provides direct evidence of natural selection, as does the declining

effectiveness of antibiotics as new, resistant strains of bacteria have evolved.

Since Darwin’s time, the evidence that living organisms adapt and evolve

through natural selection has become overwhelming, which is why Darwin’s

idea is the key to modern biological science, with applications in many

different areas of life—from the design of pharmaceuticals to the use of DNA

in the courtroom. But how were the very ¿ rst living organisms created? That

is the question tackled in the next lecture. Ŷ

Christian, Maps of Time, chap. 4.

Mayr, One Long Argument.

Darwin, On the Origin of Species.

Jones, Almost Like a Whale.

Watson, The Double Helix.

1. How did Darwin counter contemporary objections to the theory of
   natural selection?


2. What new evidence in support of Darwin’s theory has emerged since
   his death?

Essential Reading

Supplementary Reading

Questions to Consider