On the Origin of Species HTML version

On The Imperfection Of The Geological Record
On the absence of intermediate varieties at the present day -- On the nature of extinct
intermediate varieties; on their number -- On the lapse of time, as inferred from the rate
of denudation and of deposition number -- On the lapse of time as estimated by years --
On the poorness of our palaeontological collections -- On the intermittence of geological
formations -- On the denudation of granitic areas -- On the absence of intermediate
varieties in any one formation -- On the sudden appearance of groups of species -- On
their sudden appearance in the lowest known fossiliferous strata -- Antiquity of the
habitable earth.
In the sixth chapter I enumerated the chief objections which might be justly urged against
the views maintained in this volume. Most of them have now been discussed. One,
namely, the distinctness of specific forms and their not being blended together by
innumerable transitional links, is a very obvious difficulty. I assigned reasons why such
links do not commonly occur at the present day under the circumstances apparently most
favourable for their presence, namely, on an extensive and continuous area with
graduated physical conditions. I endeavoured to show, that the life of each species
depends in a more important manner on the presence of other already defined organic
forms, than on climate, and, therefore, that the really governing conditions of life do not
graduate away quite insensibly like heat or moisture. I endeavoured, also, to show that
intermediate varieties, from existing in lesser numbers than the forms which they
connect, will generally be beaten out and exterminated during the course of further
modification and improvement. The main cause, however, of innumerable intermediate
links not now occurring everywhere throughout nature depends, on the very process of
natural selection, through which new varieties continually take the places of and supplant
their parent-forms. But just in proportion as this process of extermination has acted on an
enormous scale, so must the number of intermediate varieties, which have formerly
existed, be truly enormous. Why then is not every geological formation and every stratum
full of such intermediate links? Geology assuredly does not reveal any such finely
graduated organic chain; and this, perhaps, is the most obvious and serious objection
which can be urged against my theory. The explanation lies, as I believe, in the extreme
imperfection of the geological record.
In the first place, it should always be borne in mind what sort of intermediate forms must,
on the theory, have formerly existed. I have found it difficult, when looking at any two
species, to avoid picturing to myself forms DIRECTLY intermediate between them. But
this is a wholly false view; we should always look for forms intermediate between each
species and a common but unknown progenitor; and the progenitor will generally have
differed in some respects from all its modified descendants. To give a simple illustration:
the fantail and pouter pigeons are both descended from the rock-pigeon; if we possessed
all the intermediate varieties which have ever existed, we should have an extremely close
series between both and the rock-pigeon; but we should have no varieties directly
intermediate between the fantail and pouter; none, for instance, combining a tail
somewhat expanded with a crop somewhat enlarged, the characteristic features of these