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
Where:
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, 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 “descent with modification” and established his theory of natural selection. He does not use the word "evolution" but he does say:
quote:
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:
quote:
"This earth, certainly a moderate number of millions of years ago, was a red-hot globe ... ."[29]
and after the book was published he
quote:
... 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), and this predicted that there was a mechanism for 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 “evolution consists primarily of changes in the frequencies of alleles between one generation and another as a result of genetic drift, gene flow, and natural selection” ...
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 “evolution, simply put, is descent with modification”
The
University of Michigan defines evolution as “changes in the genetic composition of a population with the passage of each generation” and the “gradual 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 diversity” ...
The
Massachusetts Institute of Technology (MIT) (Population Genetics) definition is “evolution is a change in the frequency of alleles within the gene pool of a population from one generation to the next”
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."
quote:
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.
Conclusions
(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.
Enjoy.
Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click)
we are limited in our ability to understand
by our ability to understand
RebelAAmericanOZen[Deist
... to learn ... to think ... to live ... to laugh ...
to share.
™ Version 4.2