Welcome to Defenders, the teaching class of Dr. William Lane Craig.

Today, the creation of life and biological diversity, part 31.

For more information and resources from Dr. Craig, go to reasonable faith.org.

In our last class, we saw that the word evolution is an accordion word with a wide variety

of meanings.

Specifically, we identified three senses in which the word is often used.

First, it's used to simply describe dissent with modification.

At the most, this would imply the thesis of common ancestry, that all organisms are descended

from a prior organism.

Secondly, it can be used as a description of the evolutionary tree of life, a reconstruction of evolutionary history.

And thirdly, it can be used to describe the mechanisms for evolutionary change.

In the Neo-Darwinian synthesis, this refers to random mutation and natural selection. And we saw, according to

Francisco Ayala, one of the most eminent evolutionary biologists of our day, that although

biologists accept evolution as a fact in the first sense of the word, that is to say,

dissent with modification, the other two meanings of the

word remain a matter of investigation and are often quite uncertain and even conjectural.

Now before we look in more detail at these different aspects of the current evolutionary paradigm,

I want to correct a mistake that I made in a previous class in response to a question.

This week an evolutionary biologist emailed me and said that I misspoke when I said that all of the current phila,

animal phyla that exist in the world were already present in the Cambrian and that there had been an attrition of those phyla.

And so I looked into this and what I found is that in the pre-Cambrian fossil record there

are about one to three phyla that are already attested at that point.

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