In Euclidean geometry, the shortest distance between two points is a straight line. Chern made a conjecture (cf. [10]) in 1977 that an affine maximal graph of a smooth, locally uniformly convex function on two dimensional Euclidean space R 2 must be a paraboloid. In 2000, Trudinger and Wang completed the proof of this conjecture in affine geometry (cf. [47]). (Caution: in these literatures, the term "affine geometry" refers to "equi-affine geometry".) A natural problem arises: Whether the hyperbola is a fully affine maximal curve in R 2 ? In this paper, by utilizing the evolution equations for curves, we obtain the second variational formula for fully affine extremal curves in R 2 , and show the fully affine maximal curves in R 2 are much more abundant and include the explicit curves y = x α α is a constant and α / ∈ {0, 1, 1 2 , 2} and y = x log x. At the same time, we generalize the fundamental theory of curves in higher dimensions, equipped with GA(n) = GL(n) ⋉ R n . Moreover, in fully affine plane geometry, an isoperimetric inequality is investigated, and a complete classification of the solitons for fully affine heat flow is provided. We also study the local existence, uniqueness, and long-term behavior of this fully affine heat flow. A closed embedded curve will converge to an ellipse when evolving according to the fully affine heat flow is proved.