The idea certainly pre-dates Gladwell, though it appears he was the guy that brought it from dry academia into pop-culture or whatever. A 1993 article by psychologist Anders Ericsson and others discuss the 10,000 hour rule, as well as the "ten year" rule (basically the same concept), citing research mostly on the latter that goes back a hundred years.
The main thing to keep in mind, and something that is included in Ericsson's article, is that this rule is descriptive, not prescriptive. The rule isn't "practice this long and you'll be an expert," it's "experts generally have this amount of deliberate practice behind them."
For those interested in the dry academia of it all, from the authors' conclusion:
"We view elite performance as the product of a decade or more of maximal efforts to improve performance in a domain through an optimal distribution of deliberate practice."
The authors acknowledge that practice alone doesn't cut it, and elite performers in any field also have advantages not related to length of practice alone:
"Contemporary elite performers have overcome a number of constraints. They have obtained early access to instructors, maintained high levels of deliberate practice throughout development, received continued parental and environmental support, and avoided disease and injury. When one considers in addition the prerequisite motivation necessary to engage in deliberate practice every day for years and decades, when most children and adolescents of similar ages engage in play and leisure, the real constraints on the acquisition of expert performance become apparent."
-Ericsson, K. A., Krampe, R. T., & Tesch-Römer, C. (1993). The role of deliberate practice in the acquisition of expert performance. Psychological review, 100(3), 363.
The main thing to keep in mind, and something that is included in Ericsson's article, is that this rule is descriptive, not prescriptive. The rule isn't "practice this long and you'll be an expert," it's "experts generally have this amount of deliberate practice behind them."
For those interested in the dry academia of it all, from the authors' conclusion:
"We view elite performance as the product of a decade or more of maximal efforts to improve performance in a domain through an optimal distribution of deliberate practice."
The authors acknowledge that practice alone doesn't cut it, and elite performers in any field also have advantages not related to length of practice alone:
"Contemporary elite performers have overcome a number of constraints. They have obtained early access to instructors, maintained high levels of deliberate practice throughout development, received continued parental and environmental support, and avoided disease and injury. When one considers in addition the prerequisite motivation necessary to engage in deliberate practice every day for years and decades, when most children and adolescents of similar ages engage in play and leisure, the real constraints on the acquisition of expert performance become apparent."
-Ericsson, K. A., Krampe, R. T., & Tesch-Römer, C. (1993). The role of deliberate practice in the acquisition of expert performance. Psychological review, 100(3), 363.