From: the other end of the sidewalk
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Message 1 of 108 (440999)
12-15-2007 6:57 PM
There are several threads (definition of evolution, definition of the theory of evolution, etc) and posts that mention evolution on this forum, but I want to discuss what evolution is - as a process, as a theory and as a scientific field of study - in one combined thread, and what any competing ideas regarding evolution involve and how we can test concepts of evolution against reality to determine which concepts explain the evidence and which ones do it best.
We'll start with the process, where evolution is the change in hereditary traits in populations from generation to generation
trait is an aspect that can be quantified, such as an allele or variation of a gene, the length of a bone, the size of a skull, the color of an eye, the thickness of hair,
change is a measurable quantifiable difference in a trait, such as the number, length or color,
hereditary means that it is passed from parent to child,
population means a group of individual organisms of the same species, and
generation is the average time it takes for a newborn to become able to reproduce.
You don't have to take my word for this, you can look these up and see how they are used, just be sure to stick to usage within the science of biology, seeing as that is what we are talking about.
Evolution is a process that is observed in everyday life: there is no species that does not change hereditary traits in populations from generation to generation. This process is an observed fact, and this is the objective evidential basis for the "Theory of Evolution" (ToE), and then both become the foundation of the science of Evolutionary Biology.
Astute creationists will notice that this is "just variation and adaptation within kinds" or "microevolution" which has become a well accepted fact even in these circles (as has a heliocentric solar system). That's the good news: creationists should not be concerned about evolution as defined here. The next question then is "what is the controversy all about," and how does this relate to "the rest of the story."
Darwin, Descent with Modification and Time
On 24 November 1859 Darwin published On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life, where he first described â€œdescent with modificationâ€ and established his theory of natural selection. He does not use the word "evolution" but he does say:
He who can read Sir Charles Lyell's grand work on the Principles of Geology, which the future historian will recognise as having produced a revolution in natural science, yet does not admit how incomprehensibly vast have been the past periods of time, may at once close this volume.
When the views entertained in this volume on the origin of species, or when analogous views are generally admitted, we can dimly foresee that there will be a considerable revolution in natural history.
At that time geologists and other scientists had already determined that the earth was much older than was previously thought. He refers to Lyell's "the Principles of Geology" as one reference to geological age. Meanwhile, Lord Kelvin working from principles of thermodynamics shortly before Darwin's book had come to the conclusion that:
"This earth, certainly a moderate number of millions of years ago, was a red-hot globe ... ."
and after the book was published he
... settled on an estimate that the Earth was 20-40 million years old. Shortly before his death however, Becquerel's discovery of radioactivity and Marie Curie's studies with uranium ores provided the insight into the 'energy source beyond' that would power the sun for the long time-span required by the theory of evolution.
This means that at that time the minimum age of the earth from sources outside biology was 20 million years, and probably a lot older due to the addition of radioactivity into the equations.
Darwin came to his conclusions based on comparison to animal breeding and his discoveries of existing life in various parts of the world, most notably the Galapagos Islands. He based his concept on what he knew about existing life, not on the fossil record. Not on rocks, organic soup or single cell organisms, and not on the evolution of man (his book on The descent of man, and selection in relation to sex was published in 1871). He noticed that life changed (modification), that those changes were hereditary (descent), that natural selection had to be involved because there were more offspring produced than were necessary, and that this predicted that there was a mechanism for developing new traits and transferring hereditary information from one generation to the next even though he did not know what it was.
Embryology, Evolution and Genetics
In 1900 the work of Mendel (originally published in 1866) was rediscovered by scientists working on plant physiology and then it was spread to embryology by Bateson, and this led to the further developments in biology by Haeckel, de Beers and others, leading to the use of the term evolution in studying how life develops and (ultimately) to genetics and the study of how genetic hereditary traits are passed from parent to offspring. While genetics was able to show that traits were inherited through chromosomes and genes, it took until the 1950's to link this to DNA. During that time there were a lot of theories that were proposed tested and discarded on how hereditary traits where physically transferred from parent to child before the truth was finally understood.
From 1936 to 1947 the modern synthesis was developed to combine the study of genetics with Darwinism based on morphology and fossils, and they concluded that â€œevolution consists primarily of changes in the frequencies of alleles between one generation and another as a result of genetic drift, gene flow, and natural selectionâ€ ...
Definitions used in Science
Evolutionary Biology is taught by many universities as part of their various degree programs for biologists, culminating in Ph.D.s, so if we want to look for modern definitions of evolution as used in science then we can look to how universities that teach these programs define it.
the University of California Museum of Paleontology, Berkeley definition is â€œevolution, simply put, is descent with modificationâ€
The University of Michigan defines evolution as â€œchanges in the genetic composition of a population with the passage of each generationâ€ and the â€œgradual change of living things from one form into another over the course of time, the origin of species and lineages by descent of living forms from ancestral forms, and the generation of diversityâ€ ...
The Massachusetts Institute of Technology (MIT) (Population Genetics) definition is â€œevolution is a change in the frequency of alleles within the gene pool of a population from one generation to the nextâ€
One of the areas where evolution has seen new developments is the field of evolutionary developmental biology, "a field of biology that compares the developmental processes of different animals and plants in an attempt to determine the ancestral relationship between organisms and how developmental processes evolved."
Some evo-devo researchers see themselves as extending and enhancing the modern synthesis by incorporating into it findings of molecular genetics and developmental biology. Others, drawing on findings of discordances between genotype and phenotype and epigenetic mechanisms of development, are mounting an explicit challenge to neo-Darwinism.
This can also include the effects of environment on the development of individual genotypes into adult forms, the phenotype that is the subject of natural selection.
(1) The scientific definitions from universities are consistent with the definition that evolution is the change in hereditary traits in populations from generation to generation,
(2) That this is consistent with "variation and adaptation within kinds" or "microevolution" as used by creationists, and thus that creationists should not be concerned about evolution as defined here.
(3) This thread is long enough already.
But wait --- what's the BIG LIE?
The big lie is what creationists say about evolution, that evolution is a problem for creationist beliefs, that there is something else to evolution than the change in hereditary traits in populations from generation to generation or that this is NOT evolution (but will they define what is?).
If nobody objects to this definition of evolution, or you just agree to it for the sake of the argument, then we can move on to what the definition of "the Theory of Evolution" (ToE) contains, and see what develops, something that is a problem for creationism.
Edited by RAZD, : added
Edited by RAZD, : pop in def list
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Member (Idle past 2525 days)
From: Leicester, UK
Message 14 of 108 (441321)
12-17-2007 3:12 AM
Reply to: Message 11 by Beretta
12-17-2007 1:34 AM
Re: Icon Problems
|Well quite simply if gradualistic evolution is true, what about the cambrian explosion which defies explanation in gradualistic terms.|
The simple answer to this is that the term "explosion" is misleading. The diversification of organisms in this period is estimated to have occurred over a range of about 30 million years. What's more, in order to be available to us as fossils, certain conditions must be met in the biochemical makeup of the organism, and the conditions in which it died; the sparseness of the pre-Cambrian fossil record is believed to reflect some difficulties in meeting those conditions. You can read about it here.
However, if you look at RAZD's definition of evolutionary theory, he talked about it being a synthesis of different theories. Lack of gradualism is often only apparent rather than factual, and this topic has already been addressed in theories by well-known evolutionary scientists, Gould and Eldredge for example.
Your list at the end of this post is OT here as we are discussing the definition of evolution, the theory of evolution, and evolutionary biology. However, I have seen each one of these things addressed in other topics on the forum if you'd care to have a look.
|This message is a reply to:|
| ||Message 11 by Beretta, posted 12-17-2007 1:34 AM|| ||Beretta has responded|
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| ||Message 20 by Beretta, posted 12-17-2007 7:32 AM|| ||Kitsune has not yet responded|