Over 99 percent of the species that ever walked, flew, or slithered upon this earth are now extinct. This fact alone appears to rule out intelligent design.I don't really know where to begin in critiquing such nonsense. Perhaps I should start by saying that it doesn't even come close to being an argument, but is nothing but bald, unsubstantiated opinion. To get from the single premise ('99% of species that have lived are now extinct') to the conclusion ('living things cannot have been designed') requires so many intermediate premises, each of which would require support the likes of which Harris' book is entirely devoid, that it's difficult to imagine that anyone would be persuaded by such claims.
Another thing that might be pointed out is that this pseudo-argument is not scientific, but metaphysical (religious). (This true, by the way, of most of Darwin's arguments and most of those made by his modern defenders.) Harris has here placed himself in the role of designer of life (God), and determined that he wouldn't have done it that way. Apparently, Harris' concept of a supreme, self-existent Being who created the entire universe includes the requirement that He be satisfied with creating life once and once only, and not allowing any such creations to die out. We do not, of course, require the same of either human artists or human designers, giving them instead the freedom to shelve or discard some of their works.
More importantly, this is not a claim about God from the Judeo-Christian Scriptures, which state quite the opposite (in Psalm 104, for example)--that the Creator God reserves the right to give life and to take it away, to create and to re-create. And since the Judeo-Christian God is the one toward which most of Harris' illogical venom is directed, the rules of argumentation would require that he address that God and not a straw-man of his own imagination.
But to see just how ludicrous Harris' claim here is, consider a comparable one...
Over 99% of all dialing telephones are no longer in use. This fact alone appears to rule out the idea that they were designed in the first place.Like living things, some early telephones are still extant, and many of the extinct ones can be found in museums. Far more are buried or lost, never again to see the light of day. And like extinct living things, one possible refutation of the silly claim about phones is that their designer didn't intend that they would last forever, or even remain the most advanced iteration for all of time.
As with most of the subjects Harris has the audacity to address, he's way in over his head with regard to the history of life on earth. What scientists are beginning to understand is that early life forms were perfectly suited for the conditions on earth at the time in which they lived, that later forms could not have survived those quite different earlier conditions, and that the earlier forms played key roles in making earth (including its atmosphere, oceans, crust, and other aspects) suitable for the later forms. In short, the entire history of life on earth--including the many extinction events--absolutely demands the very conclusion of design that Harris' weak pseudo-argument seeks to deny.