... But since that acts to preserve the current allele frequencies it does not result even in microevolution!
If it causes a change in the frequency of alleles then microevolution occurs. Selection for stasis is still evolution.
But the Theory of evolution requires much more. Since it hypothesizes ascent from a microbial ancestor ...
Wrong, and this is the kind of error one makes when one starts with a wrong definition for the ToE.
Note that I am referring to your definition for the ToE in Message 7:
quote:The Theory of Evolution is the theory that all the living forms in the world have arisen from a single source which itself arose naturally from an inorganic form.
All the ToE (scientific version) says is that mutations occur and cause variation in the inheritable traits, and selection operates on those variations by allowing the individuals with traits that are a better fit for the ecological challenges and opportunities to survive and reproduce. When that ecology is static and the population has reached an equilibrium fitness, selection will work to maintain a stasis in the population.
... the evidence must show that beneficial mutations that increase the genome can occur in a cumulative manner within the time available. Deleterious changes do not support that at all.
Actually all the evidence needs to show is that inheritable traits change over time, that anagenesis and cladogenesis do actually occur ... and it does.
Darwin had sufficient evidence to propose this as a hypothesis but the evidence since then is predominantly against it.
And I have no idea where you are getting this false information/idea. All scientific studies of evolution confirm evolution occurring, you can see it in every generation of every species currently living.
Again, you appear to be working with your problematic (misleading) definition of the ToE that "ascent" must occur, evolution must climb a ladder, when this is not what the ToE (scientific version) says.
But the Theory of evolution requires much more. Since it hypothesizes ascent from a microbial ancestor with a minimal genome (which appeared by unspecified magical means) the evidence must show that beneficial mutations that increase the genome can occur in a cumulative manner within the time available.
First . . .
Do you consider the evolution of humans from a common ancestor shared with other apes to be macroevolution. If so . . .
Of the genetic differences between humans and chimps, which of those are you saying that evolution could not produce?
Darwin’s theory of evolution entails the following fundamental ideas. The first three ideas were already under discussion among earlier and contemporaneous naturalists working on the “species problem” as Darwin began his research. Darwin’s original contributions were the mechanism of natural selection and copious amounts of evidence for evolutionary change from many sources. He also provided thoughtful explanations of the consequences of evolution for our understanding of the history of life and modern biological diversity.
Species (populations of interbreeding organisms) change over time and space. The representatives of species living today differ from those that lived in the recent past, and populations in different geographic regions today differ slightly in form or behavior. These differences extend into the fossil record, which provides ample support for this claim.
All organisms share common ancestors with other organisms. Over time, populations may divide into different species, which share a common ancestral population. Far enough back in time, any pair of organisms shares a common ancestor. For example, humans shared a common ancestor with chimpanzees about eight million years ago, with whales about 60 million years ago, and with kangaroos over 100 million years ago. Shared ancestry explains the similarities of organisms that are classified together: their similarities reflect the inheritance of traits from a common ancestor.
Evolutionary change is gradual and slow in Darwin’s view. This claim was supported by the long episodes of gradual change in organisms in the fossil record and the fact that no naturalist had observed the sudden appearance of a new species in Darwin’s time. Since then, biologists and paleontologists have documented a broad spectrum of slow to rapid rates of evolutionary change within lineages.
The primary mechanism of change over time is natural selection, elaborated below. This mechanism causes changes in the properties (traits) of organisms within lineages from generation to generation.
The Process of Natural Selection
Darwin’s process of natural selection has four components.
Variation. Organisms (within populations) exhibit individual variation in appearance and behavior. These variations may involve body size, hair color, facial markings, voice properties, or number of offspring. On the other hand, some traits show little to no variation among individuals—for example, number of eyes in vertebrates.
Inheritance. Some traits are consistently passed on from parent to offspring. Such traits are heritable, whereas other traits are strongly influenced by environmental conditions and show weak heritability.
High rate of population growth. Most populations have more offspring each year than local resources can support leading to a struggle for resources. Each generation experiences substantial mortality.
Differential survival and reproduction. Individuals possessing traits well suited for the struggle for local resources will contribute more offspring to the next generation.
From one generation to the next, the struggle for resources (what Darwin called the “struggle for existence”) will favor individuals with some variations over others and thereby change the frequency of traits within the population. This process is natural selection. The traits that confer an advantage to those individuals who leave more offspring are called adaptations.
In order for natural selection to operate on a trait, the trait must possess heritable variation and must confer an advantage in the competition for resources. If one of these requirements does not occur, then the trait does not experience natural selection. (We now know that such traits may change by other evolutionary mechanisms that have been discovered since Darwin’s time.)
Natural selection operates by comparative advantage, not an absolute standard of design. “…as natural selection acts by competition for resources, it adapts the inhabitants of each country only in relation to the degree of perfection of their associates” (Charles Darwin, On the Origin of Species, 1859).
During the twentieth century, genetics was integrated with Darwin’s mechanism, allowing us to evaluate natural selection as the differential survival and reproduction of genotypes, corresponding to particular phenotypes. Natural selection can only work on existing variation within a population. Such variations arise by mutation, a change in some part of the genetic code for a trait. Mutations arise by chance and without foresight for the potential advantage or disadvantage of the mutation. In other words, variations do not arise because they are needed.
Today we continue a three-lecture sequence on biological, or organic, evolution. Evolution is a unifying theme of this course, and the concept of evolution is relevant to many of our topics.
The word "evolution" does not apply exclusively to biological evolution. The universe and our solar system have developed out of the explosion of matter that began our known universe. Chemical elements have evolved from simpler matter. Life has evolved from non-life, and complex organisms from simpler forms. Languages, religions, and political systems all evolve. Hence, evolution is an appropriate theme for a course on global change.
The core aspects of evolution are "change" and the role of history, in that past events have an influence over what changes occur subsequently. In biological evolution this might mean that complex organisms arise out of simpler ancestors - though be aware that this is an over-simplification not acceptable to a more advanced discussion of evolution.
A full discussion of evolution requires a detailed explanation of genetics, because science has given us a good understanding of the genetic basis of evolution. It also requires an investigation of the differences that characterize species, genera, indeed the entire tree of life, because these are the phenomena that the theory of evolution seeks to explain.
We will begin with observed patterns of similarities and differences among species, because this is what Darwin knew about. The genetic basis for evolution only began to be integrated into evolutionary theory in the 1930's and 1940's. We will add genetics into our understanding of evolution through a discussion activity.
Definitions of Biological Evolution
We begin with two working definitions of biological evolution, which capture these two facets of genetics and differences among life forms. Then we will ask what is a species, and how does a species arise?
Changes in the genetic composition of a population with the passage of each generation
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
Note that the first definition emphasizes genetic change. It commonly is referred to as microevolution. The second definition emphasizes the appearance of new, physically distinct life forms that can be grouped with similar appearing life forms in a taxonomic hierarchy. It commonly is referred to as macroevolution.
The link to the third lecture no longer works (it repeats the second lecture above).
Definition 1 is what results from process of evolution in a breeding population, while definition 2 is what results from the processes of anagenesis and cladogenesis, which are the long term, multigenerational, accumulation of the results of the process of evolution in a breeding population.
These are pretty standard definitions, and you can find similar definitions on other university websites.
Biological evolution, simply put, is descent with modification. This definition encompasses small-scale evolution (changes in gene frequency in a population from one generation to the next) and large-scale evolution (the descent of different species from a common ancestor over many generations). Evolution helps us to understand the history of life.
The explanation Biological evolution is not simply a matter of change over time. Lots of things change over time: trees lose their leaves, mountain ranges rise and erode, but they aren't examples of biological evolution because they don't involve descent through genetic inheritance.
A genealogy illustrates change with inheritance over a small number of years.
Over a large number of years, evolution produces tremendous diversity in forms of life.
As you can (or should be able to) see these two sources provide the same basic definition.
You can also compare these to my definition:
(1) The process of evolution involves changes in the composition of hereditary traits, and changes to the frequency of their distributions within breeding populations from generation to generation, in response to ecological challenges and opportunities for growth, development, survival and reproductive success in changing or different habitats.
This is sometimes called microevolution, however this is the process through which all species evolve and all evolution occurs at the breeding population level.
If we look at the continued effects of evolution over many generations, the accumulation of changes from generation to generation may become sufficient for individuals to develop combinations of traits that are observably different from the ancestral parent population.
(2) The process of lineal change within species is sometimes called phyletic speciation, or anagenesis.
If anagenesis was all that occurred, then all life would be one species, readily sharing DNA via horizontal transfer (asexual) and interbreeding (sexual) and various combinations. This is not the case, however, because there is a second process that results in multiple species and increases the diversity of life.
(3) The process of divergent speciation, or cladogenesis, involves the division of a parent population into two or more reproductively isolated daughter populations, which then are free to (micro) evolve independently of each other.
The process of anagenesis, with the accumulation of changes over many generations, is an observed, known objective fact, and not an untested hypothesis.
The process of cladogenesis, with the subsequent formation of a branching nested genealogy of descent from common ancestor populations is an observed, known objective fact, and not an untested hypothesis.
This means that the basic processes of "macroevolution" are observed, known objective facts, and not untested hypothesies, even if major groups of species are not observed forming (which would take many many generations).
(4) The Theory of Evolution (ToE), stated in simple terms, is that the process of anagenesis, and the process of cladogenesis, are sufficient to explain the diversity of life as we know it, from the fossil record, from the genetic record, from the historic record, and from everyday record of the life we observe in the world all around us.
This theory is tested by experiments and field observations carried out as part of the science of evolution.
Reference required to the official definition of the TOE (scientific version).
"We conducted association studies by using markers in candidate pigmentation genes and discovered four mutations in the melanocortin-1-receptor gene, Mc1r, that seem to be responsible for adaptive melanism in one population of lava-dwelling pocket mice." http://www.pnas.org/content/100/9/5268.full
Thanks for that information from Universities of Michigan and Berkley, it’s most interesting.
I agree with you that “There is no single "official" definition of the Theory of Definition. Definitions 1 & 2 given in the first quote are definitions of the process of micro and macroevolution respectively. Neither is a definition of the Theory of Evolution. As you say “Definition 1 is what results from process of evolution in a breeding population, while definition 2 is what results from the processes of anagenesis and cladogenesis, which are the long term, multigenerational, accumulation of the results of the process of evolution in a breeding population.”
From Michigan we get Universal Common Ancestry, “Far enough back in time, any pair of organisms shares a common ancestor.” Abiogenesis, “Life has evolved from non-life, and complex organisms from simpler forms.” This is an assumption prior to rather part of the process of evolution. Microevolution, “Definition 1: Changes in the genetic composition of a population with the passage of each generation. … [this] “definition emphasizes genetic change. It commonly is referred to as microevolution.” Macroevolution, “Definition 2: 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. … [this] “emphasizes the appearance of new, physically distinct life forms that can be grouped with similar appearing life forms in a taxonomic hierarchy. It commonly is referred to as macroevolution.”
Similarly from Berkley Universal Common Ancestry, “Through the process of descent with modification, the common ancestor of life on Earth gave rise to the fantastic diversity that we see documented in the fossil record and around us today. Evolution means that we're all distant cousins: humans and oak trees, hummingbirds and whales.” Abiogenesis, they include as an event in “Important events in the history of life”, “Unicellular life evolves. So according to Berkley and Michigan all life evolved from a common microbial ancestor that arose naturally from non-living matter. Microevolution, is evolution on a small scale — within a single population. That means narrowing our focus to one branch of the tree of life. Biologists who study evolution at this level define evolution as a change in gene frequency within a population. Macroevolution, generally refers to evolution above the species level.
So both sources appear to agree with what is included in the theory of evolution.