Instinct, habit, and the Baldwin effect: how do the inherited and the acquired combine in evolution?

C. Lloyd Morgan, answered from the texts and cited to the page.

The position in brief

Acquired habits are not inherited — the Lamarckian hope is vain, for what an animal learns dies with it. And yet learning is not therefore idle in evolution. An animal that can learn to meet a new condition survives where the unplastic perish, and so the capacity to acquire the right habit is itself selected, and the stock is steered, over generations, toward the instinct that the habit foreshadowed.1 Plasticity guides evolution without violating heredity — this is organic selection.2345

Sources

  1. It is not that intelligence has any direct influence tending to undermine the hereditary foundations of instinct, for acquired plasticity is not inherited as such; it is rather that when the stereotyped and the plastic are pitted against each other in the struggle for existence in the wider, freer, and more varied life of the higher animals the plastic survives and the stereotyped succumbs.
    Animal Behaviour, p. 176
  2. In the merely organic phase of evolution race-progress is due, either (1) to nnfnr nl in l i 1 M i n i Ihrn n gh the elimination of nnfftv^nrflhi" TO "' nt;m °; or (2) jo t he direct inheritance or tr ansmission of the resu its of modification in certain adaptive directions! or (3) to an inherent tendency of variations to occur in such adaptive directions; or (4) to some combination of these factors.
    Habit and Instinct, pp. 279–281
  3. Trace the ancestry of any cell in the adult body, say a nerve-cell, and you reach the fertilized ovum. Trace back the ancestral line yet further, and you follow a long sequence of reproductive cells, or, at least, of cells which have undergone but little differentiation; but never again will you find, in the course of a genealogy of bewildering length, a nerve-cell.
    Animal Behaviour, pp. 36–37
  4. And in the course of a number of generations the new instinct would reach the fully adaptive level, and further modification by intelligence would become unnecessary unless the environment continued to change yet more.
    Animal Behaviour, pp. 175–176
  5. We have to take into account acquired stability due to habit as well as congenital stability due to heredity. The three factors are, therefore, (1) congenital stability, (2) youthful plasticity, and (3) acquired stability.
    Habit and Instinct, pp. 286–287

Where the argument is made

  • Habit and Instinct (1896)
  • the co-formulation, with Baldwin and Osborn, of organic selection (the Baldwin effect)

How the argument was received

This I hold as one of the soundest things I helped to see: it saves the real role of learning in evolution without the false coin of Lamarckism. That the mechanism was long neglected and is only now rediscovered under the study of plasticity I regard as a vindication deferred.