 Wallace was critical of Darwin’s claim, defended extensively in The Descent of Man (1871) that many human behaviors are grounded in instincts that are shared with other species. In his essay, “On instinct in man and animals,” (1891) Wallace presented alternative explanations for how allegedly instinctive human behaviors might be acquired by learning (Gross 2010). In a paper entitled “The philosophy of birds’ nests”, Wallace argued that Darwin was wrong even about the instinctive basis of animal behavior: