Chamber of ....Secrets?

[Carol]

No: HPFGUIDX 186000

Carol earlier:
> > If any previous Heir had appeared, both Tom and Dumbledore would
> have known it if only because the Chamber of Secrets would have been
> opened. 
> 
> Kemper responded:
> You mean any previous heir to /open/ the chamber.  I agree.  That
doesn't mean that there were no students of Slytherin's bloodline to
have gone to Hogwarts. 

Carol:
I take "the Heir of Slytherin" to mean the one true heir who not only
is descended from Slytherin (obviously, Slytherin had at least one
child who in turn had descendants clear down to Tom) but can open the
chamber. (See below.)
> 
Carol earlier:
> > ...
> > As for an absence of competent Slytherins who predate Tom, we have
Slughorn, for one, and Phineas Nigellus for another.
> 
> Kemper now:
> I was referring to the heirs of Slytherin's apparent lack of
ambition/competence and not to students in Slytherin.  Snape was more
than competent, magically not socially.  :)

Carol responds:
I didn't mention Snape (who, of course, is both intelligent and more
than competent magically) because I thought you were referring to
Slytherin students in general *before* Tom Riddle's time. (In Harry's
time, we have several Slytherins intelligent and hard-working enough
to get an O in Potions: Draco, Blaise, and Theo among them.) If you
mean students with the last name Slytherin, I expect that the last
name (the male line) died out quickly. Maybe Slytherin had a daughter
or granddaughter who married into another Pure-Blood family. A few
generations later, a great-great-granddaughter (or whatever) must have
married Cadmus Peverell, and that male line also died out, with the
last Peverell daughter marrying a Gaunt. Eventually, the only people
known to have Slytherin ancestry were the Gaunts, who started marrying
each other. 

Be that as it may, the question is whether any students of Slytherin's
bloodline actually attended Hogwarts and why none of them qualified as
what Diary!Tom called Slytherin's "true heir." I agree that, before
the Gaunt era, most if not all of Slytherin's descendants would have
attended Hogwarts (most if not all of them Sorted into Slytherin). I
see no reason why his direct descendants wouldn't have attended
Hogwarts until several of the male lines (Slytherin and Peverell among
them) had died out. But, clearly, none of those students was the Heir
of Slytherin in the sense that Diary!Tom uses the word. The *true*
heir of Slytherin would have to be not only intelligent, ambitious, 
magically gifted, and highly motivated to root "unworthy" students out
of Hogwarts, but also a Parselmouth--the exact combination of traits
that we find in Slytherin himself and in his distant descendant, Tom
Riddle. Every Slytherin descendant before him must have been lacking
in one or more of those key components. Either they lacked the
motivation to open the Chamber of Secrets and release the monster, or
they lacked the ability, or both.

The Peverell blood would, perhaps, have temporarily reinforced the
traits of ambition, intelligence, and magical power in Slytherin's
descendants (who would have continued to attend Hogwarts), but since
no (true) Heir of Slytherin appeared, those students must not have
been Parselmouths. (I'm sure that they knew they were descended from
both Salazar Slytherin and Cadmus Peverell, given that even Marvolo
Gaunt knew his ancestry, and quite possibly they were Pure-blood
supremacists, but either they thought that the Chamber of Secrets was
just a legend or they lacked the ability to open it. None was the
*true* Heir of Slytherin, not only as intelligent and ambitious and
magically gifted and virulently anti-Muggle as Slytherin himself, but
able to hear the Basilisk roaming through the pipes, find its hidden
chamber, and control it as Tom did. He alone had all the qualities
required to become Slytherin's true heir.)

I conjecture that once Slytherin ancestry was (apparently) restricted
to the Gaunts and they started intermarrying, both ambition and
intelligence dwindled, but the gene (or combination of genes) for
Parseltongue resurfaced. Poor and ignorant but regarding themselves as
special, they apparently stopped attending Hogwarts, or, if they
attended, they quickly dropped out. Parseltongue alone did not make
Marvolo or his children "true heirs." Only Tom, with a combination of
qualities resembling those in Slytherin himself, could hear the
Basilisk and open the chamber.

Carol, realizing that this post is mostly speculation but trying to
account for the absence of a "true heir" in the nearly one thousand
years between Salazar and Tom