Okay, but I still don't see any scientific evidence the claim that 98% or 99% of all species have become extinct. Perhaps you may want to point out exactly where the scientific evidence can be found in your references? Thank you.
Precisely what are you willing to accept as "scientific evidence?" Do you expect Percy's reference to have a listing of all of the billions of species estimated to have existed on Earth throughout history? Do you require documentation of a specific fossil for every species that is believed to have ever existed, despite the fact that fossilization is an extremely rare event and many organisms (including bacteria and other single-celled organisms) simply do not leave fossils? Are you willing to accept a mathematical extrapolation from the number of known species from the fossil record? Given that the number is in fact an "estimate," will you immediately challenge the admitted imprecision of the number, even though it's likely to be accurate, regardless of Percy's response? Do you even understand the difference between precision and accuracy, or will you conflate the two in an attempt to "prove" that the imprecision of an estimate means it's somehow likely to be inaccurate in its entirety?
What if only 90% of the species that have ever existed are now extinct? Would your argument change? Would it change at 80%? At 50%? Because even if it's an absurdly low number like 10%, we know that our hominid ancestors are all extinct, even though it's extremely unlikely to find evidence for a specific cause for the extinction of a specific species. Does the manner of extinction particularly matter when determining whether those hominid ancestors were actually the ancestors of modern humanity? Does it matter whether a branch of our ancient cousins were killed off in a natural disaster because they all lived in a single geographic area, or whether they were simply out-competed by a new branch of the family tree? What's the relevance?
Is there some reason that you think that reversing the typical "if humans descended from apes, why are there still apes" argument into the equally vapid "if humans are descended from apes, why are all the human-ancestor apes extinct" is particularly clever? Why do you think that the Theory of Evolution requires ancestor species to survive to be contemporary with all of their descendants? By that logic, you should be asking "if birds descended from dinosaurs, why aren't there any dinosaurs living today?" After all, we don't see "sub-birds" and "sub-sub-birds" flapping their not-quite-flight-capable wings around today either. I wouldn't expect to, but for some reason you seem to. Why?
Perhaps a more obvious metaphor would be useful.
How come there is no ape species more human like than chimps or bonobos? Why is there such a huge gap? You would expect to find living gradations of species leading up to human, right? There should be sub-humans and sub-sub-humans and sub-sub-sub humans walking around.
"How come there is no members of my family tree more like me than my cousins? Why is there such a huge gap? You would expect to find all of our shared ancestors like parents and grandparents and great-grandparents leading up to me, right? All of my family before me from my father to my grandfather to my great-great grandfather should be walking around."
The fact that most of my ancestors are dead has no logical bearing on whether or not my cousins and second-cousins and other more distant relatives who still breathe are actually related to me.
Why then do you believe that the ancestors of our species must be alive to prove our relation to the distant cousins of humanity that are alive today?
“The human understanding when it has once adopted an opinion (either as being the received opinion or as being agreeable to itself) draws all things else to support and agree with it.” - Francis Bacon
"There are two novels that can change a bookish fourteen-year old's life: The Lord of the Rings and Atlas Shrugged. One is a childish fantasy that often engenders a lifelong obsession with its unbelievable heroes, leading to an emotionally stunted, socially crippled adulthood, unable to deal with the real world. The other, of course, involves orcs." - John Rogers