Our thoughts are more in a language we are most familiar with, and vice versa. I.e., we can't think in Latin if we don't know the language. Means, even if someone has the intellect/capacity to think, we can't actually think or plan if we don't know/been taught a language. We'd just be relying on our reflexes always.
You don't need language to think, but language helps you think more intricately. Obviously a lot of thought goes into planning physical activities.
Musicians, carpenters, sculptors, obviously many people spend much of their day thinking in ways other than language.
To humanity, what'd have come first? thoughts (the key to intelligence and science) or language?
Fortunately we've been able to observe this phenomenon by teaching ASL (American Sign Language) to our closest relatives, the chimpanzees and gorillas.
In the wild they perform very complicated, coordinated tasks, so it's clear that they're thinking. When they learn ASL, they can share their thoughts with others. This makes the entire
community stronger.
Anthropologists and archeologists say it's very likely that the technology of spoken language was invented about 70KYA. This is when we see an explosion of complicated, coordinated activities that could not possibly have been performed by people who were also using their hands to signal.
It's interesting that only 10,000 years later, humans finally migrated out of Africa and established communities that survived and prospered. In a strange place with different weather, food, predators, etc.--that would be difficult to do without speech.