Does high-level intellectual performance depend on practice alone? Debunking the Polgar sisters case

The famous Polgar sisters started chess very young, undertook extensive study, and two became grandmasters. This case often is cited as decisive evidence that practice alone is key in development of expertise, that innate talent is unimportant or non-existent, and that almost anyone can become a grandmaster. But on close examination these claims do not hold up. Performance differences among the sisters cannot be accounted for by practice differences. Furthermore, two sisters reached peak performance levels comparable to those of many far less-practiced players entering the international domain around the same time and only one sister ever reached the top ten. Contrary to a popular view, the case does not show that becoming a grandmaster requires only practice and raises innate talent as a plausible contributor.