"Brit-Am Now"-366
February 25, 2004
Food for thought
The following extracts are taken from
Lee M. Spetner, "Not by Chance," 1996
In our opinion the explanation for the phenomenon observed
is due to inbuilt genetic potential being activated.
This may also be the opinion of the author.
p.16-17
Wynne Edwards [1986] has suggested that animals generally manage their
food resources by controlling their own numbers. Populations are kept in
check not by the extrinsic forces of mass starvation or disease, but by the
intrinsic forces built into the animals themselves. This phenomenon may be
surprising and even amazing to most people, but biologists studying animals
in the wild have reported this kind of control operating in a variety of
populations
[Wynne-Edwards 1965, 1986: Wynne-Edwards, V.C., (1965). Self-regulating
systems in populations of animals,Science, vol. 147, pp. 1543-1548).
Wynne-Edwards, V.C., (1986). Evolution Through Group Selection, London:
Blackwell.; Bergerud 1983 : Bergerud A.T., (1983). Prey switching in a
simple ecosystem,Scientific American, vol. 249, December.].
Plants also do not proliferate in a field to the point where
they become crowded. They do not engage in a struggle for existence where
natural selection would preserve the strong and destroy the weak. Plants
tend to control their populations by sensing the density of the planting.
When the growth is dense, plants produce less seeds; when growth is thin,
they produce more seeds [ Bradshaw 1965: Bradshaw, A.D., (1965).
Evolutionary significance of phenotypic plasticity in plants,Advances in
Genetics, vol. 13, pp.115-155.]
p.65-67
There are some alleles in populations that have proved to be useful in the
past. But you cant expect to find new genes lying around that can play a
useful role they never played before. Alleles that have been useful in the
past do get stored in a population, and are found in large numbers, closer
to thousands than to 1. That may be why, when useful genes are found, there
are so many of them. They might be left over from what was once a large
fraction of the population, and maybe selection pressure has not yet got
rid of them.
Genes that were once useful but arent now, could still sit in
the population. The more there are,the longer they can stay dormant in the
population. Some genes would be adaptive now if they could get put together
right. They may need only a recombination or an inversion to reawaken them.
Others could be in the population in working order, but would not be
adaptive now. They could lurk there, hardly noticed, until they are needed
once more. When they are needed they would be selected , and their numbers
would grow. Such examples would not demonstrate the effect of random
variation.
Alcohol resistance in vinegar flies is an example of an
allele that lurks in the population in working order. The gene for it
exists in functional form in a small part of the population [McDonald, et
al. 1977: McDonald J.F., G.K. Chambers, J. David, and F. J. Ayala, (1977).
Adaptive response due to changes in gene regulation: a study with
Drosophila,Proceedings National Academy of Sciences, USA, vol. 74, pp.
4562-4566.].
Some resistant flies are in the population all the time. Their numbers
increase when conditions select for them.
Another example is the peppered moth, which Kettlewell first
reported in the 1950s [Kettlewell 1955, 1959, 1973: Kettlewell, H.B.D.,
(1955). Selection experiments on industrial melanism in the
Lepidoptera,Proceedings Royal Society, B, vol. 145, pp. 297-303.
Kettlewell, H.B.D., (1959). Darwins missing evidence,Scientific
American vol. 200, March.
Kettlewell, H.B.D., (1973). The Evolution of Melanism: the Study of a
Recurring Necessity with Special Industrial Melanism in the Lepidoptera,
Oxford University Press.].
Since then many evolutionists have cited it as a odd example of Darwinian
evolution in action. The peppered moth has changed from a light to a dark
color and then back to a light color, and it seems to have done so through
natural selection.
The peppered moths live in Great Britain. Before the coming of industry
with its pollution they were of a light color peppered with dark spots.
Normally, the moths spend their days on lichen-covered tree trunks. The
moths spotted light color serves as a camouflage against the background of
the light-colored lichens and protect it from birds that prey on it. The
rise of industry in Britain spread soot in the industrial areas, and the
soot blacked the buildings and trees. On the soot-blackened background the
moths light color was no longer a camouflage. But within the 100 years (or
less) the moth population in industrial areas evolved a protective dark
color. In the rural areas, however, most of the moths remained light.
Melanin is the protein that gives the dark color to the skin
and hair of animals. The skin cells of dark moths make more melanin than
the light moths do, and thats what makes them dark.
Pollution control in the industrial areas was started in the
1960s and has since cleaned up the environment. After the air was cleaned
of soot, the lichen-covered tree trunks regained their light color. The
moths have also, to a large extent, returned to their former light color
[Cook et al. 1986 : Cook, L.M., G.S. Mania and M.E. Varley, (1986)
Postindustrial Melanism in the Peppered Moth,Science, vol. 231, pp. 611-613.].
Evolutionists often cite industrial melanism as an example of
evolution. Although it may be an example of natural selection, it is not
an example of random variation. It turns out that when the soot began to
cover the lichens, the light-moth population didnt have to wait for a
mutation to turn dark. The dark moth was already in the population. It was
living as a small minority among the light moths. [Bishop and Cook 1975:
Bishop, J.A. and L. M. Cook, (1975). Moths, melanism and clean
air,Scientific American, vol. 232, January.]. Where the tree trunks are
light, most of the moths are light colored. Where the tree trunks are
sooty, most of the moths are dark. There was no random variation. Both
types of moths have been living side by side in both environments.
p.198-199
Plants and animals hardly ever increase their numbers so much that they
exhaust their resources. They stop increasing well before they deplete
their habitat. Animals are mobile and can disperse when they are
overcrowded, but plants require other strategies. Some plants
adjust their seed production to their density. It has been discovered
that if plants are set close together, they will produce less seeds than if
they are set further apart. Linseed plants, for example, have been
reported to produce almost sixteen times as many seeds per plant when they
are set far apart as when they are set close together. Other plants react
to variations f density by varying the numbers of their leaves or the
lengths of their stems. [ Bradshaw 1965: Bradshaw, A.D., (1965).
Evolutionary significance of phenotypic plasticity in plants,Advances in
Genetics, vol. 13, pp.115-155.]
A Mediterranean grass has been reported to increase its
flowering by a factor of a hundred when it was moved from less fertile to
more fertile ground [ Bradshaw 1965: Bradshaw, A.D., (1965). Evolutionary
significance of phenotypic plasticity in plants,Advances in Genetics, vol.
13, pp.115-155.]. Several species of plants vary their stem height, stem
number, and flowering time as conditions vary from sunshine to shade and
from wet to dry. [ Bradshaw 1965: Bradshaw, A.D., (1965). Evolutionary
significance of phenotypic plasticity in plants,Advances in Genetics, vol.
13, pp.115-155.]
Crabs prey on snails with thin shells, but they cannot eat
snails that have thick shells. Snails can somehow tell if crabs are
around. In the presence of crabs they grow a thick shell [Stearns 1989:
Stearns , S.C., (1989). The evolutionary significance of phenotypic
plasticity,BioScience, vol. 39, pp.436-445.] This adaptation clearly helps
protect the snails from the crabs.
Snails are themselves predators. They prey on barnacles. When
the barnacle senses snails, it protects itself by growing into a bent-over
shape that keeps the snails from eating it. When there are no snails
around, the barnacle develops into its normal straight form. [Stearns
1989: Stearns , S.C., (1989). The evolutionary significance of
phenotypic plasticity,BioScience, vol. 39, pp.436-445.Lively 1986: Lively
C.M., (1986). Predator-induced shell dimorphism in the acorn barnacle
Chthamalus anisopoma,Evolution, vol. 40, pp. 232-242.]
I am suggesting here that the organisms have a built in capability of
adapting to their environment. I am suggesting that to the extent that
evolution occurs, it occurs at the level of the organism. This suggestion
differs sharply from the thesis of the NDT, which holds that evolution
occurs only at the level of the population.]
p.200
Finches are the family of birds we see most. The comprise the largest
family (Fringillidae) of the largest order (Passeriformes) of the class of
birds. In many parts of the world there are more finches than there are
other birds, both in the number of individuals and in the number of their
species. Also known as sparrows and warblers, the finches are the most
diversified of all bird families. Their evolution has been studied more
than any other bird family.
The Galapagos Islands lie isolated in the Pacific Ocean. They straddle the
equator, and are about 650 miles west of mainland South America. Darwin
visited these Islands on his famous voyage on the H.M.S. Beagle. Among the
birds on the islands, he found finches that looked like finches elsewhere,
but they were not the same as any he had seen before. He collected
samples of nine species of them and brought them back with him to England.
p. 202
Laysan Island is a small coral island in the Pacific Ocean about a thousand
miles northwest of Honolulu. It stands not much more than 10 feet out of
the water. Laysan Island together with three other small islands in its
vicinity form an official US Government Bird Reservation, which is the
largest protected bird colony in the world. In 1967 about a hundred
finches from Laysan were broght to a small atoll, called Southeat Island,
about three hundred miles northwest of Laysan and about a hundred miles
southeast of Midway Island. Southeat Island belongs to a group of four
small islands all within a radius of about ten miles.
Through natural dispersion, and with some human help, the
finches spread to all four islands of the group. When the birds were
checked in 1984 they were already found to be different from the Laysan
finches [Conant 1988: Conant S., (1988). Saving endangered species by
translocation,BioScience, vol. 38, pp. 254-257; Pimm 1988: Pimm S. L.,
(1988). Rapid morphological change in an introduced bird,Trends in
Evolution and Ecology, vol. 3, pp. 290-291]. By 1987 the population of
finches had grown to about 800. when the birds were first put on
Southeast Island in 1967 they were all alike. But when they were studied
twenty years later. Birds on different islands were found to differ from
each other. In particular, they were found to have different bill
shapes. The bills on the birds of North Island, about 10 miles north of
Southeat Island, are deeper and shorter than those on either Southeast or
Laysan. The birds on Southeast have longer bills than those on Laysan.
How did these differences arise so fast? To suggest the changes came from
random variation and natural selection is unreasonable.
p. 203
A change to a new species could occur quickly, even in one generation.
Thomas Smith, of the University of California at Berkley,
studied an African finch in Cameroon. He found that the finches can produce
offspring having two different bill sizes. He found this to be true in all
three species of finch that he studied[Smith 1987: Smith, T.B., (1987).
Bill size polymorphism and intraspecific niche utilization in an African
finch,Nature, vol. 329, pp. 717-719.]. he did not say whether or not the
environment played any role in the producing of two bill sizes. But he did
report that the bill sizes are adaptive, each in its own niche. The birds
with large bills crack large hard seeds easily, while those with small
bills do so only with difficulty. The birds with small bills, on the other
hand, feed more efficiently on small soft seeds than do those with large
bills. These results show that bill size in finches can change from one
adaptive type to another with diet.
p.204
There is a cichlid fish, of species alta that preys on large mature
guppies. The killfish preys on small immature guppies. Normally, guppies
that live with the alta mature earlier and produce more ands smaller
offspring than do those that live with killfish. The Aripo River in
Trinidad has guppies together with alta cichlids , and the guppies that
live there follow this rule. Reznick and his team took 200 guppies from
the Arpo and put them in the tributary of the river that is home to the
killfish but has no cichlids and had no guppies. Changes soon appeared in
the newly introduced guppies. The fish population soon changed to what
would normally be found in the presence of the killfish, and Reznick found
the changes to be heritable.
The full change in the guppy population was observed as soon as the first
samples were drawn, which was after only two years. Reznick interpreted
these changes as the result of natural selection acting on variation
already in the population. Could natural selection have acted as fast as to
change the entire population in only two years? A more reasonable
explanation is that the presence of the predator induced the changes in the
individual fish.
p.205-206
* Limbs that protrude from an animals body have more surface area per
unit mass than the rest of the body. In cold weather the animal loses more
heat per unit mass from these limbs than from other parts of the body. In
may species the tails and legs are shorter for those living in colder
climates and larger for those in warmer climates. Gullswings are shorter
in cold climates than in warm. Hares and foxes also have shorter ears in
colder climates than in warm. Eskimos have shorter arms and legs than do
people living in warmer climates [Collier et al. 1973: Collier, B.D.,
G.W. Cox, A.W. Johnson, and P.C. Miller, (1973). Dynamic Ecology,
Englewood Cliffs: Prentice-Hall.]. Sumner [1909] found that mice reared at
low temperature had shorter legs and tails than mice reared at higher
temperatures [Johnson and Gottlieb 1990: Johnston, T.D. and G. Gottlieb,
(1990). Neophenogenesis: a developmental theory of phenotypic
evolution,Journal of Theoretical Biology, vol. 147, pp. 471-495.].
* Glogers rule: Races of birds or mammals living in cool dry regions
have lighter skins than do races of the same species living in a warm
humid area [Schreider 1964: Schreider, E., (1964). Ecological rules,
body-heat regulation, and human evolution,Ecology, vol.18, pp. 1-9.]. This
is true of humans as well.
* Jodans rule: Many species of fish tend to have more vertebrae when
they live in cold water than do the same species living in warm water.
[Schreider 1964: Schreider, E., (1964). Ecological rules, body-heat
regulation, and human evolution,Ecology, vol.18, pp. 1-9.]. These
differences have been shown to depend on the temperature at which the fish
have been reared [Brooks1957: Brooks J.L., (1957). In Mayr [1957],
pp.81-123.; Hubbs 1922, 1926: Hubbs C.L., (1922). Variation in the number
of vertebrae and other meristic characters of fishes correlated with the
temperature of water during development,American Naturalist, vol. 56, p.
360-372. Hubbs C.L., (1926). The structural consequences of modification
of the developmental rate in fishes, considered in reference to certain
problems in evolution.American Naturalist, vol. 60, p. 57-81. ; Murray and
Beacham 1989: Murray C.B. and T.D. Beacham (1989). Responses of meristic
characters in chum salmon (oncorhynchus keta) to temperature changes
during development,Canadian Journal of Zoology, vol. 67, pp. 596-600. ;
Johnson and Gottlieb 1990: Johnston, T.D. and G. Gottlieb,
(1990). Neophenogenesis: a developmental theory of phenotypic
evolution,Journal of Theoretical Biology, vol. 147, pp. 471-495.]
Now Index
HOme