Does evolution depend on abiogenesis?

When discussing ‘new life forms’ that are supposed to arise from evolution, Norman Geisler and Frank Turek, in their apologetic work, I Don’t Have Enough Faith to Be an Atheist, point out that the most difficult problem for evolution is that Darwinists can’t explain where the first life came from:

If Darwinists don’t have an explanation for the first life, then what’s the point of speaking about new life forms? The process of macroevolution, if it’s possible at all, can’t even begin unless there’s preexisting life. (pg 139)

This argument is similar to one used in this article on evolution, posted on the apologetic website, Stand to Reason. Gregory Koukl, the author, states that for evolution to be a fact, two things are needed: (1) life coming from non-life (i.e., abiogenesis), and (2) change in that life from simple forms to complex forms over time. He then states that nobody knows how life arose, and then argues:

Evolution is claimed to be a fact, but you can't have the fact of evolution unless you have the fact of abiogenesis. Yet nobody knows how such a thing could ever take place. And if life can't be shown to have come from non-life, then the game can't even get started.

One thing is correct in the above argument: scientists don’t yet know how first life arose, although there are some tantalising theories (see here). But is it then valid to argue that evolution is not true because we don’t know how abiogenesis occurred? I don’t think it is.

The above argument does not consider the fact that we can actually observe evolution happening. Many new species have been observed to have formed through evolutionary processes (see here for examples). Not only can we see evolution happening but there are many clues, from many different spheres of research, that suggest that evolution has occurred throughout the ages (see here). The evidence for evolution is so good that evolutionary theory does not depend at all on the validity of abiogenesis. In other words, evolution happens, irrespective of what we know (or don’t know) about the formation of first life.

I will highlight the weakness of the argument further with this analogy. It is not a perfect analogy but it will do the trick. Humankind has only recently, over the last few centuries, discovered the exact process involved in conception. Would it be logical for someone in the Middle Ages, for example, to deny that humans physically grow from babies into adults because Middle Age society lacks complete knowledge of how life begins in the womb?

No. This conclusion is fallacious in that we can observe people growing and developing physically all around us. In other words, physical development in a human individual happens, irrespective of what we know (or don’t know) about the formation of life in the womb.

So not only is this argument an appeal to ignorance, but it also wrongly assumes that the truth of evolution somehow depends on the validity of abiogenesis.