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Re: The extinction of small dinosaurs



HP Rob Gay commented:
I roundly reject the "disease as mega-killer" hypothesis, because it would
be equivalent to a disease that killed all mammals. A) diseases aren't
successful from an evolutionary standpoint, if they kill all their
hosts...they'll die out B) No known disease has such a widespread effect
today. Even things like Ebola, which can be carried in other mammals
(closely related to us, I hasten to add), it isn't deadly to them. No doubt
when landbridges were opened, some diseases were carried across by the
immigrant dinosaurs, but I sincerely doubt that they ever decimated whole
species.

The ability of a disease to survive depends on how long it takes to kill its
victims.  It just needs time to spread.
Also, a disease can mutate into a deadly form, damaging a population
severely and then disappear, or even mutate again.
Certainty should be treasured for its rarity.
For what it's worth, I think that diseases by themselves would not destroy a
population.  But diseases carried by a competitive species which is
significantly more immune could do a lot of damage.

I'm wondering if a recent speculation from genetic research wouldn't prove
the possibility, if true.  According to a recent article about dog dna (the
one speculating dogs were domesticated once, in Asia), dogs whose ancestry
can be traced to the period before the arrival of Europeans disappeared in
the Americas after the arrival of the newcomers.
Given the affection for and utility of dogs, I have trouble with the notion
that the aboriginal dogs were made extinct in a brief period by their
owners.  If not, then what better explanation than disease and competition?