Humanity’s current understanding of magic leads us to believe that it has been a fundamental property of the universe since the Big Bang. Every organism with what we call ‘consciousness’ has the potential to use magic. In the natural world, most organisms will, by chance, use magic to their advantage at least once during their lifespan, but these are sporadic and unfocused anomalies. Creatures with higher levels of consciousness have better chances at reproducing these effects, but the chances are still slim in comparison to humans.
Magical species both novel and familiar have emerged. Over millions of years, these magic-using creatures gradually refined and focused their use of magic into something reliable and practical, and have turned it into their primary weapon or defense mechanism. For humans in the past, this meant that learning magic greatly increased your chance of survival, and magic schools became a staple of the common education system during ancient times, at least 20,000 years ago.
Due to this constant usage, nearly all humans nowadays exhibit minuscule magical traits from birth, and we have to work slightly less hard to learn magic than our ancient ancestors did. It’s still far from easy, though. With the advantage of formal education, it’s common for humans to learn and master magic within their lifespan.
Just as talent in other skills is not evenly distributed, capacity for and natural skill in magic is distributed likewise. There are prodigies that can learn very quickly, while others must work much harder to achieve the same level of proficiency.
Regardless, learning magic is difficult, and it always takes upwards five to ten years of vigorous study and practice before a student can be considered an Apprentice; a title granted when the student demonstrates that they can reliably and effectively call upon their magic, —e.g., a fire user causes a row of wooden pegs to ignite simultaneously. All variations of magic require great focus and skill to use consistently, and thus it is not commonly used by the less experienced in casual settings.