[sittnick]

So, there is no "present-day cockroach." There are many different species in the cockroach family. Yet, we call them all cockroaches. Evolution at work.

Yeah, and we call lots of different critters "bugs", that doesn't mean that one came from another. We can use a (purportedly) 50,000 year old horse, if you like. It would be harder to revive.

And of course, our naming system is somewhat arbitrary. We group things together according to similarities but the construct is of course, artificial by definition. (e.g. by one standard peanuts are regarded as nuts, but by others they are not nuts).

[Alter Kaker]

We can use a (purportedly) 50,000 year old horse, if you like.

A 50,000 year old member of the equus genus would likely not have been able to easily breed with a modern horse. Equine evolution has been remarkably well documented.

We group things together according to similarities but the construct is of course, artificial by definition. (e.g. by one standard peanuts are regarded as nuts, but by others they are not nuts).

Huh? Peanuts are not nuts, they are legumes. I don't believe that there is any taxonimical controversy over their classification.