[forgottenpaswrd]

"What if our brain is actually a multi core machine that has millions of cores?"

The brain has billions of cores on parallel units, but they are unconscious.

"Would you still force it to use one core?"

No, you can't use only one at all, but you use "the one",the conscious brain(that could only do one thing at the same time) to coordinate them all, you should "force" the millions of cores to work in the same thing at the same time.

"I think humans were built to multitask, our environment is too complex to be single threaded, think driving: you need o pay attention to multiply things at the same time."

They were built to multi task over the same thing. If you go hunting but you are also thinking on your girlfriend while you remember the taste of the food you ate yesterday and try your nephew does not get hurt you won't be as efficient as someone that focus all their senses and thoughts over one single task.