"I don't believe innate talent exists" - This, in light of 100 years of (mathematized quantitative genetics) and thousands of years of empirical observation, is a profoundly wrong observation. There is variation in, broadly speaking, traits and (almost) all physiological and behavioral traits are heritable. Do you believe that taller parents tend to have taller offspring? I guess the answer is yes; then, it is not any different for other traits that are less-observable, for example control of motor functions.
There is a time, early in life, during which traits are more plastic, for a variety of reasons (for height, nutritional interventions are more likely to be successful early in life than during the teenage years), but you won't make a genetically slow phenotype into a top 1% 100-m specialist.
There is a time, early in life, during which traits are more plastic, for a variety of reasons (for height, nutritional interventions are more likely to be successful early in life than during the teenage years), but you won't make a genetically slow phenotype into a top 1% 100-m specialist.