Why do humans need to cook raw food ?

i'm doing coursework for science chemistry, and i'm not too sure on why humans need to cook raw food, is it something to do with bacteria ?Why do humans need to cook raw food ?
some meats and poultry harbor bacteria that can make humans ill

we lack the enzymes to destroy the little beasties so we must apply heat. If you were to ingest said bacteria they would multiply inside you and you would become sick and possibly die depending on the type of bacteria

raw fruits vegetables and grains and most fish do not harbor said beasties hence you can eat an apple right of the treeWhy do humans need to cook raw food ?
Meats have nasty bacteria like e-coli, salmonella, %26amp; listeria.

All of these have been in the news, this past year.

Freezing %26amp; cooking will control these forms of contamination.

Many vegetables contain fibre which is more digestible if cooked.Why do humans need to cook raw food ?
Meat has bacteria that can be fatal to humans such as Salmonella, E.Coli, etc.

We were talking about it today in school