Why Tom? (re: wizard genetics and long-lived)

[littleleahstill]

No: HPFGUIDX 101227

In COS, Diary Tom tells Harry that they are probably the only 
Parseltongues to attend Hogwarts in the last 1000 years.  As we know, 
but Diary Tom didn't, Harry's ability to talk to snakes is not 
innate, but was transferred to him at Godric's Hollow. So, if we take 
Diary Tom's word for it, he is the only Parseltongue to attend 
Hogwarts in the last 1000 years.  Is the ability to speak 
Parseltongue genetic?  If so, that's one heck of a recessive gene- 
and why would it be activated in a witch/muggle mating?  It doesn't 
appear to be possible to learn it, considering the many gifted 
wizards who can't do it.

We know Tom is the Heir because he can open the Chamber, but is it 
anywhere directly said that his mother is descended from Salazar? I 
thought it was in COS, but I can't find it.  Who did Salazar have 
this family with? Choosing Rowena or Helga would make Tom the Heir of 
Ravenclaw and Hufflepuff as well, which seems unlikely, so can we 
assume a child born during his wanderings post-Hogwarts.  Perhaps the 
Parseltongue gene descended from Salazar through a very long line of 
squibs, and was activated by Tom Snr's marriage to a witch. That's a 
nice thought.

Or could Parseltongue have been a gift of VaporMort? I like this one, 
but Harry needed Parseltongue to access the chamber, so I assume the 
same would have applied to Tom.

Am I missing something here?

Leah