[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
New Species, etc.
There are several good examples of new species having been created in the
laboratory. Among the plants, there is Raphanobrassica, an artificial hybrid
between the cabbage and the radish. It is highly fertile
with itself, but infertile with either parent. Normally, C x R crosses
yield sterile offspring, but if the chromosomes are doubled by treatment
with colchicine, the C set can pair with its homolog and the R set with
its. The resulting tetraploid plant is highly fertile. Alas, most varieties
so far combined the worst characters of both parents, the tough root of the
cabbage with the coarse leaves of the radish.
A second plant example is Triticale, an artificial hybrid between wheat
and rye and the first new grain crop since the Middle Ages. It is grown
in cold climates both for grain and I think for animal food.
Actually, remote hybridization and spontaneous chromosome doubling
is not uncommon in nature among plants. It is rare among animals because
sex determination in many animals is chromosomal and generating
tetraploids may disrupt sex determination.
An animal example is furnished by fruit flies. It is possible to select
populations of Drosophila over many generations in the laboratory that
can no longer interbreed with their wild forebearers. Formally, they are
a new species, but one might argue they are still Drosophilids. Still,
this is a good model for allopatric speciation.
In the case of crosses in both directions between horses and asses,
the progeny are sterile. Male mules fail to make good sperm, but the
reciprocal cross, the hinny, may occasionally be fertile as a female.
Female mules are usually sterile, but there is a Roman proverb, "Cum
mula peperit," "If a mule foals," or "Once in a blue moon," used to
describe rare events. So, perhaps it does happen. Scientific American
had an article on the subject back in the 60's or 70's.
Crosses between fish species are sometimes fertile, but in some cases,
the offspring develop tumors.
It is probable that the red wolf, the subject of great conservation
efforts, is a natural hybrid between the coyote and the grey wolf.
In this case, the offspring were fully fertile and had normal chromosome
I believe a posted a summary of remote hybridization from a short lived
hybrid LIST to Skeptic last year. If there is sufficient interest and I can
find it, I'll repost it.
The point is that genuine new species have been created in the laboratory
by mechanisms analogous to those observed in Nature. Species aren't
fixed, nor are they "baramins," the creationist term for 'created kinds"
coined from Hebrew by Morris (I'm not sure the "n" is not a second "m", not
being a Semiticist.)
In reply to Gilgamesh's recent statements, the first land animals are
thought to be detritivores living on semi-decayed plant material and the
bacteria growing on them. This is because plants in general are toxic
as well as hard to digest and partial degradation not only makes
the residue more digestible, it also may detoxify it. In modern organisms,
most of the work is done by the digestive tract, liver, kidney, etc,
but many herbivores still require symbiotic bacteria to digest plants.
There were algae, cyanobacteria and other lower plants near the shores
and in shallow or tidal areas which could have supported a food chain.
One doesn't need large land plants to support a near shore community of
at least partially terrestrial animals. In any case, I thought eurypterids
were aquatic, but I could be wrong.