92 J.J. Haldane
of contemporary evolutionary theory it is conceded that not every significant
characteristic, organ or power is an evolutionary adaptation.
That selection is not a necessary condition of species development may not
be so troubling given the general presumption of evolution. More problem-
atic is the suggestion that it might not be sufficient: that a further cause may
need to be operative. The standard evolutionary account of speciation is in
terms of cumulative selection. That is to say, very roughly, it is supposed that
the origination of one species from another is not by a single step (that would
defy belief ) but by progressive sifting and sorting as the product of one
selection is then subjected to further selection, and so on. Think, for example,
of a gardener who wants to grow large, strong vegetables but currently has
only small, frail flowers. He could try planting the seeds from the latter and
waiting until spring but it would be a miracle if these seeds developed into
what he wanted. However, if he were patient and lived long enough, then he
might proceed by gathering seeds from the largest and strongest of the flowers,
planting these, training and nurturing the seedlings eliminating the weaker
ones; then gathering the seeds from the largest and strongest plants, and so
on. It would be less surprising if eventually cumulative selection proved effect-
ive in leading to the development of a species of the desired sort.
Purged of intention and agency this is how evolutionary theory explains
development. Notice, however, that cumulative selection presupposes some
form of replication possessed by the original and intervening living entities.
They need to have some mechanism of reproduction. This is a feature to be
explained by selection no less than others, but it is hard to see how it can be.
Selection purports to explain adaptive features of which replication is prime;
but it operates over generations, and successive generations only come into
existence because of the replicative powers of their ancestors. These powers
cannot themselves be the product of cumulative selection. So, contrary to
its implausibility, the claim has to be that their emergence occurred in a
single step; somehow non-replicating entities just ‘turned into’ reproducing
species.
A likely rejoinder to this observation will be the claim that the initial step
was not to full-scale reproduction but to proto-replication. Organic reproduc-
tion proceeds asexually or sexually. In the first case parts of the organism
become detached and form new individuals; and in the second, special cells
( gametes) are formed within individuals, and the joining of these in fertiliza-
tion yields a cell that develops into an individual of the same type as its
parents. The selection of advantageous parts and powers is made possible
because of the inheritance by one generation of features possessed by the
previous one, and the transmission of the same or relatively similar character-
istics to its offspring. One way of regarding this process is in terms of the
transmission of organizational information through enduring and reliable