as evidenced by fossil foraminifera, for example. Darwin recognized this criticism
and addressed it in the third edition of Origin:
But it may be objected that if all organic beings thus tend to rise in the scale, how is it that
throughout the world a multitude of the lowest forms still exist; and how is it that in each
great class some forms are far more highly developed than others? Why have not the more
highly developed forms everywhere supplanted and exterminated the lower? . . . On my
theory the present existence of lowly organised productions offers no difficulty; for natural
selection includes no necessary and universal law of advancement or development—it only
takes advantage of such variations as arise and are beneficial to each creature under its
complex relations of life. And it may be asked what advantage, as far as we can see, would it
be to an infusorian animalcule—to an intestinal worm—or even to an earth-worm, to be
highly organised? If it were no advantage, these forms would be left by natural selection
unimproved or but little improved; and might remain for indefinite ages in their present little
advanced condition. (Darwin 1861 pp. 134-5)
2.4 Biogeography of Infusoria
Biogeography was a major point in Darwin’s formulation of his theories of Evolution and Natural Selection (Richardson 1981). While on the Beagle voyage and
during the analysis of his samples afterward, he recognized that the distribution of
animals and plants could not be explained by special creation of creatures that were
designed for the habitat they occupied. Instead, their distribution could be better
explained by migration of creatures between locations and the subsequent adaptation
of the founding population to the local conditions in the new environments. He
especially observed this in the animals of South America and the Galapagos Islands.
Darwin said in his “Essay of 1844” (quoted in Richardson 1981):
I think then I am justified in asserting that most of the above enumerated and often trivial
points in the geographical distribution of past and present organisms (which points must be
viewed by the creationists as so many ultimate facts) follow as a simple consequence of
specific forms being mutable and of their being adapted by natural selection to diverse ends,
conjoined with their powers of dispersal, and the geologico-geographical changes now in
slow progress and which undoubtedly have taken place. This large class of facts being thus
explained, far more than counterbalances many separate difficulties and apparent objections
in convincing my mind of the truth of this theory of common descent.
In 1844 Darwin turned to the German naturalist Christian Gottfried Ehrenberg to
include infusoria, or in modern terminology Protista, in his biogeographic studies
(Fig. 2.2). This was perhaps the only time that he included microorganisms directly
in his work. Darwin was alerted to Ehrenberg’s interest in the geographic distribution of infusoria by his German publisher, Ernst Dieffenbach. In April 1844, Darwin
wrote to Ehrenberg for the first time offering to send him samples he had collected
from the Galapagos Islands and Tierra del Fuego, along with samples provided by
his friend, the botanist Joseph Dalton Hooker who had sailed on an Antarctic
expedition (Darwin Correspondence Project Letter no. 747 2019a). While on the
Beagle voyage, he collected soil and rock samples from various locations as well as
dust that settled on the ship while in the mid-Atlantic.
24
K. M. Noll
and addressed it in the third edition of Origin:
But it may be objected that if all organic beings thus tend to rise in the scale, how is it that
throughout the world a multitude of the lowest forms still exist; and how is it that in each
great class some forms are far more highly developed than others? Why have not the more
highly developed forms everywhere supplanted and exterminated the lower? . . . On my
theory the present existence of lowly organised productions offers no difficulty; for natural
selection includes no necessary and universal law of advancement or development—it only
takes advantage of such variations as arise and are beneficial to each creature under its
complex relations of life. And it may be asked what advantage, as far as we can see, would it
be to an infusorian animalcule—to an intestinal worm—or even to an earth-worm, to be
highly organised? If it were no advantage, these forms would be left by natural selection
unimproved or but little improved; and might remain for indefinite ages in their present little
advanced condition. (Darwin 1861 pp. 134-5)
2.4 Biogeography of Infusoria
Biogeography was a major point in Darwin’s formulation of his theories of Evolution and Natural Selection (Richardson 1981). While on the Beagle voyage and
during the analysis of his samples afterward, he recognized that the distribution of
animals and plants could not be explained by special creation of creatures that were
designed for the habitat they occupied. Instead, their distribution could be better
explained by migration of creatures between locations and the subsequent adaptation
of the founding population to the local conditions in the new environments. He
especially observed this in the animals of South America and the Galapagos Islands.
Darwin said in his “Essay of 1844” (quoted in Richardson 1981):
I think then I am justified in asserting that most of the above enumerated and often trivial
points in the geographical distribution of past and present organisms (which points must be
viewed by the creationists as so many ultimate facts) follow as a simple consequence of
specific forms being mutable and of their being adapted by natural selection to diverse ends,
conjoined with their powers of dispersal, and the geologico-geographical changes now in
slow progress and which undoubtedly have taken place. This large class of facts being thus
explained, far more than counterbalances many separate difficulties and apparent objections
in convincing my mind of the truth of this theory of common descent.
In 1844 Darwin turned to the German naturalist Christian Gottfried Ehrenberg to
include infusoria, or in modern terminology Protista, in his biogeographic studies
(Fig. 2.2). This was perhaps the only time that he included microorganisms directly
in his work. Darwin was alerted to Ehrenberg’s interest in the geographic distribution of infusoria by his German publisher, Ernst Dieffenbach. In April 1844, Darwin
wrote to Ehrenberg for the first time offering to send him samples he had collected
from the Galapagos Islands and Tierra del Fuego, along with samples provided by
his friend, the botanist Joseph Dalton Hooker who had sailed on an Antarctic
expedition (Darwin Correspondence Project Letter no. 747 2019a). While on the
Beagle voyage, he collected soil and rock samples from various locations as well as
dust that settled on the ship while in the mid-Atlantic.
24
K. M. Noll