Stargazer's ignorance of observed evolutionary change does not make it
non-existent. Your ignorance of observed evolutionary change does not
make it non-existent. Stargazer may have an excuse. You lack an excuse -
examples have been presented to you on several occasions. You can't even
"justify" your claims above by your usual resort to the epistemological
nihilism of occasionalism.
There are two classic instances of observed instance of evolution in
Gould's work on Punctuation Equilibrium. While for most taxa the fossil
record is too sparse to distinguish between Punctuated Equilibrium and
Gradualism, or to demonstrate stasis, Gould found two instances where in
a small region of time and space intermediates between two more
widespread and longer occurring species occur.
Speciation has been observed multiple times. From the book I never got
round to writing
"Among those unfamiliar with the science of biology it is widely, but
incorrectly, thought that speciation has not been observed. In fact
speciation by several different modes has been observed or replicated.
Here I focus on polyploid speciation resulting in sexually reproducing
plant species, which is relatively frequent among observed and
replicated instances of speciation, as a result of its shorter
characteristic timescale, and is less open to disputation, compared to
example the formation of new vegetatively or apomictically reproducing
taxa, or in groups with permanent odd polyploidy or permanent
translocation heterozygosity, as to whether a taxon is a genuine species.
By restricting myself to sexually reproducing species I can apply the
biological species concept wherein a species is a congeries of
populations among which individuals reproduce sexually, and which is
sufficiently isolated genetically from other species. Such species have
been observed to have originated in the wild, under cultivation, and in
the laboratory. In other cases species have been recreated
experimentally from the putative ancestors, and in yet other cases the
origins of polyploid species have been inferred from studying their
karyotype and genome.
The ancestral life cycle of plants includes an alternation of
generations between a haploid (gametophyte) generation with a single set
of chromosomes, and a diploid (sporophyte) generation with two sets of
chromosomes. (In the familiar flowering plants the gametophyte
generation is reduced to the pollen grain (male) and embryo sac
(female).) A polyploid plant has 3, 4 or more sets of chromosomes. In an
autopolyploid all the sets of chromosomes come from a single species; in
an allopolyploid the sets of chromosomes represent two or more species.
There are several processes which can result in an increase in the
number in the number of sets of chromosomes - somatic cell chromosome
duplication, formation of unreduced gametes, polyspermy and somatic cell
fusion. These processes, together with hybridisation, can and do combine
to produce new species."
Examples of observed new species in the wild include Spartina anglica,
Senecio cambrica, Tragopogon mirus, Tragopogon micellus and Mimulus
peregrinus. Example of new species emerging spontaneously under
conditions of Aesculus carnea, Digitalis mertonensis and Primula kewensis.
In the laboratory both novel species (such as Elytricum fertile) and
prexisting species (such as hexaploid wheat, tetraploid brassica and
West African okra - the last recreated in a Japanese laboratory by a
researcher unaware of the preexisting crop populations) have been
created from their parent species.
Work on sunflowers has replicated homoploid speciation.
Turning to change less drastic than speciation, there are many examples
of observed changes in allele frequencies in populations. For example
there is industrial melanism in Biston betularia and other moth species;
antibiotic resistance in bacteria; herbicide resistance in plants;
insectide resistance in mosquitoes; drug resistance in malarial
parasites; warfarin resistance in rodents; beak size in Galapagos
finches; and citric acid metabolism in E. coli.
--
alias Ernest Major