Re: new method of evolutionary change

Robin Mandell (rmandell@jpusa.chi.il.us)
Wed, 16 Dec 1998 19:02:02 -0600

At 03:55 PM 12/15/98 -0400, you wrote:
>>>A more dramatic way to build up genetic information is to duplicate
part of
>>>the genome. This can happen by unequal crossing over during meiosis or by
>>>hybridization (common in plants, rarer in animals), among other methods.
>>>As a result, the organism has extra copies of genes. As long as one stays
>>>functional, mutations in another copy may provide novel functions.
>>>
>>Is there an example of this today? Talk down I am on the edge of not really
>>getting 1/2 of this.
>
>In plants, hybridization often leads to the production of a new species
>with an extra set of genes. Many agriculturally important species have
>this, including wheat, corn, at least some species of cotton, and most
>seedless fruit (including bananas). It has been done deliberately in the
>lab (a Soviet scientist crossed cabbage and raddish and got a useless
>vegetable with cabbage roots and raddish leaves, for example), and also
>happens naturally. Another well-studied example is the marsh grass
>Spartina in England, where the native species has hybridized with some
>introduced from the U.S. Among animals, there are lizards in which hybrids
>are parthenogenic females, recognized as a distinct species. Comparing the
>amount of DNA and number of copies of genes in different species suggests
>that the vast majority of new species of plants may arise in this way. A
>plant with a strange number of chromosomes can start a population by
>asexual reproduction or by self-fertilization, but fewer animals are able
>to do these, and so it happens more rarely in animals. However, there are
>a few points in animal evolution where the amount of DNA has about doubled
>and the number of copies of certain genes has increased.
Could you name one of those points and how we are aware of a "point in
animal evolution" (if this is a long involved question maybe another book
suggestion would be better. I like just quizzing you like this but I am
sure you are busy and do not wish to impose....I think.
>More frequently, there are many gene families that appear to have arisen by
>unequal crossing over or other duplication of a small part of the genome.
>A particular example involving color vision in monkeys has been
>well-studied. Normally, this species is colorblind. A simple mutation
>changes the type of color blindness. If a normal and a mutant breed, the
>offspring will have both genes and color vision. Unequal crossing over can
>then put the two on the same chromosome, so that full color vision (by
>primate standards) is now coded by two genes rather than different versions
>of the same gene.
These colorblind mutations are natural or engineered?
>>Do you think the big jumps in life were sudden or slow and gradual?
>
>Probably some of both. The transition between reptiles and mammals, for
>example, took place by many small steps over tens of millions of years.
>However, mutations in genes that affect development can produce drastic,
>immediate changes.
>
>>Do you see it as all natural or was God directly manipulating things?
>
>I think God directly controls everything. For example, He is no less
>involved if I let go of a rock in midair and it falls to the floor than if
>it were to remain hovering without support. The vast majority of the time,
>He follows certain patterns in how He runs nature. These patterns are what
>we try to describe as natural laws. Miracles are when He does not follow
>these patterns because of some more important factor, such as revelation of
>His nature to humans. I do not see any particular evidence that He did not
>stick with patterns in the process of creeating life. The evidence neither
>requires nor rules out miracles in the process, but He seems to use them
>only when necessary, and I do not believe that they were needed for
>physical creation, except at some point in the very beginning when creation
>was started. I do not know enough physics to guess at what point this
>beginning would have been.
Here I am struggling. What do you mean by "directly controls everything.
Like if God were to blink it would all be up for grabs in the natural law
scene? Seems like God's goodness and other concepts get a bit strange if
God's will actively holds bullets on their course. What about the brain of
man? How could freedom exist? Have I missed something? On the other hand if
God sets it up and lets it go then some of what you describe like "unequal
crossing over" and even mutation begin to sound less like a creative act
and more like accidents. Any guidance here?
>>What do you think of the probability of life from non life by chance?
>
>"Chance" is a word to reagrd with suspicion in this context.
>Mathematically, there are some things that we cannot predict except by a
>general statement based on the laws of probability. These may be referred
>to as random in a technical sense. Some aspects of evolution, as far as we
>can tell, are mathematically random.
>
>However, in a more informal sense, chance can refer to a lack of oversight.
>According to the Bible, God is sovereign over mathematically random things
>such as casting lots, and over everything else. Thus, there is nothing
>that is truly chance in the sense of beyond God's oversight. (Obviously,
>people debate exactly what the role of free will is, but I think most
>people would agree that primordial soup does not have much will).
>
>I think God probably created life from non-life without using miracles,
>because He seems to use them quite sparingly and because I do not see an
>unbridgeable gap. However, there is not enough evidence to be sure.
>
>David C.
Thanks David,
Andrew