Yes. I was taking you up on a particular example, and I challenge you, anyone else, the whole world, to demonstrate that vertebrates, in general, are more "complex" than invertebrates in any meaningful sense whatsoever.
I mean can't you say that a multicellular organism is more complex than a single-celled organism?
Not without knowing more about them.
But the whole idea of "complexity" is that complex organism, the "red herring". It's not an interesting concept within evolutionary thought.
So what should you use instead? That organisms aren't more complex than others, just different from others?
There might be a sense in which some organisms could be said to be more complex than others, but from an evolutionary point of view, yes, that's about right.
I am a vertebrate, a lobster is an invertebrate. I can't see any reasonable biological sense in which one could declare that I am "more complex" than a lobster, we're just different organisms adapted to different environmental niches.
What an awful assumption to make. I can't imagine what they are thinking to conclude that it was probably lost in the chimp lineage.
They're thinking: what are the odds that not having these genes was the basal state and that just by coincidence it was added by separate but identical evolutionary events in the lineages which possess it.
In other words it's one absurd assumption compounding another crazy assumption.
Those are, to be sure, other words. But it is not the same thing in other words.
Try reading it again; and bear in mind that if you don't immediately understand something, it's not always the thing that you don't understand that is stupid. Occasionally it may be you.
Even if we were to assume that the gene evolved as you indicate, this still doesn't imply two evolutionary events.
I have no idea what you're talking about.
You make the assumption I guess on the basis that you have assumed a closer relationship between humans and chimps than other primates.
No: on the basis that chimps do not lie outside a clade which includes humans and gorillas and macaques.
Let me try to explain the reasoning by analogy. Suppose you have seen 100 of the same make of car. 99 of them have a winged horse as a hood ornament. One of them does not. If you had to chose between the following two explanations, which would you find most likely?
(1) The hood ornament is standard, but one car has lost its hood ornament. (2) Having no hood ornament is standard, but 99% of drivers have by complete coincidence chosen to accessorize their cars in exactly the same way.
Both accounts of the history of the cars is possible; but one of them is overwhelmingly more probable, is it not?