On 27/08/2014 12:43 AM, Nigel Dyer wrote:
This summer I read "On the Origin of the Species" from cover to cover
for the first time. I had not realised what a truely remarkable book
it is. It covers the dogs/wolves question in great detail.
I bought a copy but still haven't got around to reading it. Knowing
that Darwin knew nothing of genetics, I have trouble in getting excited
about anything he might have to say on the subject - which is why I
haven't read it yet. But on your recommendation maybe I should.
In some respects my day job could be described as being an
evolutionary geneticist, and it is remarkable how much of the detail
of what I work on was predicted in Darwins book. He describes in
great detail the general principles of evolution, which are backed up
by the DNA sequences that I work on.
For quite a while I have wanted to ask someone working in your field
about what DNA has to say about evolution of species so maybe now is a
good time.
I have almost no doubt that physical life on this planet has evolved
from a very simple looking self-replicating organism into the plethora
of life forms which past and present have occupied it. But the
mechanism by which this process occurs is still a complete mystery to
me. I am totally convinced (from the maths) that random processes
cannot by any means produce the complex folding proteins that are needed
for life - so the question is how did they arise? Is it possible that
the first life form (that as a minimum must have been implanted on this
planet) could have contained in some condensed form sufficient
information and machinery to evolve into all the life forms that have
occurred? Or is it necessary that some additional injection or meddling
was necessary along the way?
For instance, as I understand it, the frog was one of the first
creatures to invade the land from the sea and all land vertebrates
evolved from the frog. So one question would be, is there sufficient
information in the DNA of a frog, to have the potential of developing
(by pre-designed but natural means) into all the land animals that have
occurred (and of course the sea mammals)? Or is it necessary to
postulate some other source of DNA information which needs to be added
to the limited information available in frog DNA?
So my question is really this:- From your knowledge of the DNA content
of various life forms (and assuming the so-called "junk" DNA between
gene coding regions actually contains useful information for possible
future evolution), is there sufficient information in the DNA of simpler
looking life forms to allow them to evolve into the more complex types,
or does information need to be added?
Interestingly, Darwin discusses how if you specifically breed for
variation in a specific characteristic (his example is pigieon beak
length) then this shows greater variablity in future variations. He
also discusses how some things show a remarkable fixedness over vast
periods of time. This suggests the possibility that evolution may
proceed in fits and starts: puncutated equilibrium, and yet he then
talks very much in terms of gradual and continuous evolution, which
has become taken as the defining feature of Darwinian evolution.
Punctuated equilibrium is seen as somethiong of a heresy.
I have always felt that punctuated equilibrium was far more consistent
with the evidence, both fossil records and from DNA, and I strongly
suspect that it is associated with the DNA rearrangements that occur
occasionally (I have been looking at a virus sequence where a section
of the sequence has become inverted).
Yes you are right. Punctuated equilibrium (ie sudden and relatively
large changes) does match the evidence. I am not aware of any radically
new physical features that can be shown to have developed gradually over
time. If sufficient information was included in the original
protoplasmic life form, then it is easy to imagine how accumulated
adaptation could be designed to trigger a new physical feature to
suddenly appear, fully formed and functional, just when where and when
it is needed!
There was also a recent paper that shows that one of the differences
between the hooded crow and the black crow, which can interbreed so is
arguably a single species, is an inversion of part of the DNA
sequence. This will have occurred with one individual (a punctuation
of the equilibrium), and has subsequently allowed the two crow races
to drift away from each other, potentially leading ultimately to two
species.
