Arriving during gay pride month, Jordan Harrison’s new play explores currents of non-heterosexual identity in a nearly comprehensive way. Its characters cover the waterfront in terms of gender fluidity, with side trips to racial and class identity. Allen Moyer’s primary set is an apartment with ceiling-high bookcases and comfortable modern furniture. In spite of the elegance, however, Harrison’s characters might as well be living in the titular log cabin. They are sexual pioneers lost in a wilderness of fluctuating gender identity rather than ferocious animals and untamed nature.