I'll raise your 'Huh' with my own huh?
How does we KNOW this?
Because a saltational event in one individual is usually weeded out.
"How can a 'mutation' take place in a group and not in an individual?
I didn't say that it did. Genetic changes accumulate in a population through a number of generations not in one generation. This is obvious. A single individual may be the first to experience a mutation but unless that new allele becomes at least semi-fixed, (available to a significant proportion of the population) the population will remain genetically identical to the original species (I'm assuming an allopatric speciation scenario, sympatric would be slightly different). In sexual species, this allele can only be passed on to succeeding generations.
Where it is highly unlikely that a single mutation will result in a large enough morphological change to be considered a new species, (when using morphology as the speciation standard, something that is difficult to do) each additional mutation increases the distance between the parent and daughter species/subspecies.
Don't rail against my equivocation on species; as the word is used by science it can be very difficult to differentiate between two species and more than just morphology and/or interbreeding frequently needs to be considered - determined by the situation.
MAY???