When humans apply selection to organisms, it's called artificial selection.
It's like natural selection, but often works faster.
So about 30,000 years ago, humans began artificial selection on
the gray wolf to generate our first domesticated animal, the dog.
Different traits that were already present and
variable in the gray wolf were selected over the millenia.
Long or short legs, long or short hair, body size, skull shape,
erect versus floppy ears, etc., to general the huge diversity of domestic dog breeds.
Again, selection generated enormous complexity simply by
focusing on particular traits of interest.
Finally, I'm going to focus on a recent and ongoing example of natural
selection that's of critical importance to human health and
that's the rise of antibiotic resistant bacteria.
The discovery of antibiotics was one of the triumphs of 20th century science.
For the very first time, we could rapidly and effectively cure bacterial infections.
Your life and mine have probably been saved by antibiotics.
However, bacteria can hit back.
And just occasionally, a bacterial cell can acquire an extra piece of DNA
that confers resistance to antibiotics and
they do this by stealing it from another bacterial cell.
Natural selection by antibiotics kills all the bacteria,
except this one cell that's acquired the new gene, because it's now resistant.
As each new antibacterial compound is introduced into clinics, more and
more resistance genes can be assembled under this power of natural selection.
In fact, it's usually only a few years or
a decade before resistance to a newly introduced antibiotic is observed.
The continuing use of more and
more diverse antibiotic agents has resulted in the assembly of
highly complex DNA molecules that confer resistance to a wide, and
all of this has happened since the 1950s which is an evolutionary instant.
In each of the examples I've presented, selection that allows some
variance to reproduce at the expense of others has generated complexity and
it's done so over a comparably short period of time.
And you don't have to imagine the degree of complexity that selection on a very,
very long time period could generate,
because you just have to look at the natural world around you.
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