Coming along and scratch

1)Does "coming along" mean "bringing up"?
2)"scratch identifying marks"carve out identifiable marks"?

Context:

The logic turns out to be no more convincing than this: 'I [insert
own name] am personally unable to think of any way in which
[insert biological phenomenon] could have been built up step by
step. Therefore it is irreducibly complex. That means it is designed.'
Put it like that, and you immediately see that it is vulnerable to
some scientist coming along and finding an intermediate; or at least
imagining a plausible intermediate. Even if no scientists do come up
with an explanation, it is plain bad logic to assume that 'design'
will fare any better. The reasoning that underlies 'intelligent design'
theory is lazy and defeatist - classic 'God of the Gaps' reasoning. I
have previously dubbed it the Argument from Personal Incredulity.
Imagine that you are watching a really great magic trick. The
celebrated conjuring duo Penn and Teller have a routine in which
they simultaneously appear to shoot each other with pistols, and
each appears to catch the bullet in his teeth. Elaborate precautions
are taken to scratch identifying marks on the bullets before they are
put in the guns, the whole procedure is witnessed at close range by
volunteers from the audience who have experience of firearms, and
apparently all possibilities for trickery are eliminated. Teller's
marked bullet ends up in Penn's mouth and Penn's marked bullet
ends up in Teller's. I [Richard Dawkins] am utterly unable to think
of any way in which this could be a trick. The Argument from
Personal Incredulity screams from the depths of my prescientific
brain centres, and almost compels me to say, 'It must be a miracle.
There is no scientific explanation. It's got to be supernatural.' But
the still small voice of scientific education speaks a different
message. Penn and Teller are world-class illusionists. There is a