Evolution Pt. I  What is Evolution?

Evolution Pt. II  Fossils

Evolution Pt. III  Dating Methods

Darwin wrote:

I am fully convinced that species are not immutable; but that those belonging to what are called the same genera are lineal descendants of some other and generally extinct species, in the same manner as the acknowledged varieties of any one species are the descendants of that species. Furthermore, I am convinced that Natural Selection has been the main but not exclusive means of modification. (69) [1]

Audesirk et al. wrote:

evolution: the descent of modern organisms with modification from preexisting life-forms; strictly speaking, any change in the proportions of different genotypes in a population from one generation to the next. (G-9) [2]

Alters wrote:

evolution: a scientific theory of orgnismal change over time originally developed by Charles Darwin; it embodies the ideas that species alive today are descendants of species living long ago, and that species have changed and diverged from one another over billions of years; the process of change over time by which existing populations of organisms develop from ancestral form through modification of their characteristics. (G-10) [3]

Quote:

Evolution is any process of growth or development that entails change, but most commonly refers to biological evolution. The theory of evolution is the single unifying paradigm of biology – the current consensus among biologists is that modern life is the result of an extensive process of evolution that began several billion years ago with simple single-celled organisms. While the idea of biological evolution has existed for thousands of years, it only developed a scientific foundation in the middle of the 19th century. As the theory of evolution has become more widely accepted, it has displaced other explanations for the origins and diversity of life, such as spontaneous generation of complex organisms and creationsism. Often the word evolution is used as shorthand for the modern theory of evolution of species based uponDarwin’s idea of natural selection.


The current dominant theory of evolution is known as the "modern evolutionary synthesis" (or simply "modern synthesis"), referring to the synthesis ofDarwin’s theory of evolution by natural selection and Mendel’s theory of the gene. Within this theory, evolution may be defined as the change in the frequency of an allele within a gene pool, caused by natural selection and/or genetic drift. Such changes over long periods of time lead to major changes in phenotype. According to this theory, the fundamental event of speciation is the genetic isolation of two populations, which allows their gene pools to diverge. Since the modern synthesis, biological evolution has been defined as changes in allele frequencies in a population from one generation to another.

Dictionary.com wrote:

An assumption based on limited information or knowledge; a conjecture.

Dictionary.com wrote:

A set of statements or principles devised to explain a group facts or phenomena, especially one that has been repeatedly tested or is widely accepted and can be used to make predictions about natural phenomena.

Quote:

Calling the theory of evolution "only a theory" is, strictly speaking, true, but the idea it tries to convey is completely wrong. The argument rests on a confusion between what "theory" means in informal usage and in a scientific context. A theory, in the scientific sense, is a "coherent group of general propositions used as priniciples of explanation for a class of phenomena" [Random House American College Dictionary]. The term does not imply tentativeness or lack of certainty. Generally speaking, scientific theories differ from scientific laws only in that laws can be expressed more tersely. Being a theory implies self-consistency, agreement with observations, and usefulness. (Creationism fails to be a theory mainly because of the last point; it makes few or no specific claims about what we would expect to find, so it can’t be used for anything. When it does make falsifiable predictions, they prove to be false.)

Quote:

The essential elements of the scientific method are iterations and recursions of the following sour steps:

Characterization
Hypothesis (a theoretical, hypothetical explanation)
Prediction (logical deduction from the hypothesis)
Experiment (test of all of the above)
This can be called the hypothetic-deductive method. These activities do not describe all that scientists do (see below). The 4-step method described above is often used in education. Teachers using inquiry as a teaching method sometimes teach a slightly modified version of the scientific method in which "Question" is substituted for Observation.

Science is a social activity. The process is subject to evaluation by the scientists directly involved, or by the scientific community, at any or every stage. A scientist’s theory or proposal is accepted only after it has become known to others (usually via publication, ideally peer reviewed publication) and criticised.

Trefil & Hazen wrote:

Observations and experiments must be reported in such a way that anyone with the proper equipment can verify the results. Scientific results, in other words, must be reproducible, and they must be reproducible by anyone, not just the original experimenters (10) [4]

Gravetter & Wallnau wrote:

The null hypothesis (H0) states that in the general population there is no change, no difference, or no relationship. In the context of an experiment, H0 predicts that the independent variable (treatment) will have no effect on the dependent variable for the population. (235).

The alternative hypothesis (H1) states that there is a change, a difference, or a relationship for the general population. In the context of an experiment, H1 predicts that the independent variable (treatment) will have an effect on the dependent variable. (235) [5]

Leary wrote:

independent variable: in an experiment, the variable that is varied or manipulated by the researcher to assess its effects on participants’ behavior. (423)[6]

Leary wrote:

dependent variable: the response measured in a study...(421)[6]

Bunch et al. wrote:

Body fossils are either actual remains of organisms in which the original chemicals have been replaced by other chemicals, thus retaining the original shape but not the organic chemistry. Bones, teeth, and shells are the most common animal body fossils. Petrified wood is a common plant body fossil. Softer tissues, such as those that compose worms and leaves are less apt to be preserved; they are more likely to have been eaten or broken down by decomposers (bacteria, etc.).

Trace fossils include imprints, tracks, burrows, feces, and chemical traces. They can be very informative about the habits and habitats of their creators. They also may tell us something about the organisms’ anatomy. For example, footprint size and the distance between prints in a track provide clues to the size and weight of the animal that made the track. (211)[1]

Levin wrote:

If life has evolved, the fossils preserved in consecutive formations should exhibit those changes. Indeed, many examples are known of sequential morphological changes among related creatures during successive intervals of geologic time (120) [2]

Pojcta wrote:

The fossil record remains first and foremost among the databases that document changes in past life on Earth. Fossils provide the dimension of time to the study of life. Some of the most basic observations about fossils and the rock record were made long beforeDarwin formulated his theory of "descent with modification." The fossil record clearly shows changes in life through almost any sequence of sedimentary rock layers. Successive rock layers contain different groups or assemblages of fossil species. (3) [3]

Plummer wrote:

The oldest fossils found are prokaryotes - microscopic, single-celled organisms that lack a nucleus. These date back to around 3.5 billion years (b.y.) ago, so life on Earth is at least that old. It is likely that even more primitive organisms, similar to viruses, date back further in time but are not preserved in the fossil record. Fossils of much more complex, single-celled organisms that contained a nucleus (eukaryotes) are found in rocks as old as 1.4 b.y. These are the earliest living creatures to have reproduced sexually. Colonies of unicellular organisms likely evolved into multicellular organisms. Multicellular algae fossils date back at least a billion years. (187) [4]

Wright wrote:

Deposits inAustralia, Greenland, andSouth Africa offer a cryptic view of the earth’s surface as it was between 3.2 billion and 3.8 billion years ago. The deposits are made up of layers of accumulated particles that were later buried, heated, and compressed. Rounded pebbles and smoothed sand grains in the sediments indicate that they were seabeds, so any life they record would be marine.

The oldest fossil of that life comes from a remote desert site inWestern Australia called North Pole. The rocks there bear the marks of stromatolites – sizable mounds of mud and minerals trapped or precipitated by microbial colonies living in shadow ocean water. Modern stromatolites grow knee-high inAustralia and theBahamas, and the organisms that build them leave distinct patterns in the mud pedestal that can’t be duplicated by mere geological manipulation. (24) [5]

Pennock wrote:

...it is not at all surprising that there are "missing links" in the fossil record and this is not good evidence against evolutionary transmutation; on the contrary, given what we know, it is what we expect to see. Given the difficulties involved in fossilization in the first place the record of intermediate forms is remarkably good and continually getting better...Even more exciting is the whole new category of fossil information that advances in genetic technology are just beginning are just beginning to open up. (153). [6]

Monroe & Wincander wrote:

Dissolved minerals can be precipitated in the pores of bones, teeth, and shells or can fill the spaces within cells of wood. Wood may be preserved by silica replacing the woody tissues; it then is referred to as petrified, a term that means "to become stone". Silicon dioxice (SiO2) or iron sulfide (FeS2) can completely replace the calcium carbonate (CaCO3). Insects and the leaves, stems, and roots of plants are commonly preserved as thin carbon films that show the details of the original organism.

Shells and bones in sediment may be dissolved leaving a cavity called a mold shaped like the shell or bone. If a mold is filled in, it becomes a cast. (178-179). [7]

Alters wrote:

During the formation of sedimentary rock, dead organisms are sometimes washed along with the mud or sand and eventually reach the bottom of a pond or lake. Dead marine organisms fall to the bottom of the ocean. As the sediments harden into rock, they harden around the bodies of these dead organisms. The hard parts of these organisms, such as their skeletons, may become preserved or may be broken down and replaced with other minerals.

Sometimes, however, soft-bodied animals are preserved in exceptionally fine-grained muds, in conditions in which the supply of oxygen was poor while the muds were being deposited, thus slowing the decomposition of the organism. Eventually, the soft parts of an organism decay completely, leaving behind a mold, or impression, of its body. Mold may become filled with minerals, such as lime or silica found in underground water, forming casts, which resemble the original organism or body part. (539-540) [8]

Plummer wrote:

No matter where on Earth they are found, individual fossil species always occur in the same sequence relative to one another. By comparing fossils found in a layer of rock in one area with similar fossils in another area, we can correlate the two rock units. More accurately, we can say that both rock units formed during the span of time that the species existed on Earth. (186) [4]

Trefil & Hazen wrote:

The fossil record of horses, for example, includes a series of precursor animals beginning with one about the size of a cat some 50 million years ago, and changing through many intermediate forms up to modern times. (615) [9]

MacFadden wrote:

Fossil horses have held the limelight as evidence for evolution for several reasons. First, the familiar modern Equus is a beloved icon that provides a model for understanding its extinct relatives. Second, horses are represented by a relatively continuous and widespread 55-My evolutionary sequence. And third, important fossils continue to be discovered and new techniques developed that advance our knowledge of the Family Equidae. The fossil horse sequence is likely to remain a popular example of a phylogenetic pattern resulting from the evolutionary process. (1730) [10]

Benton & Pearson wrote:

Marine plankton appear to show gradual speciation, with subsequent morphological differentiation of lineages taking up to 500,000 years to occur. Marine invertebrates and vertebrates more commonly show punctuated patterns, with periods of rapid speciation followed by long-term stasis of species lineages. (405) [11]

Boisserie, J., Lihoreau, F., & Brunet, M. wrote:

Molecular comparisons indicate that Cetacea should be the modern sister group of hippos. This finding implies the existence of a fossil lineage linking cetaceans (first known in the early Eocene) to hippos (first known in the middle Miocene). (1537) [12]

Pojcta and Springer wrote:

In the mid-1600's about 200 years beforeDarwin published his theory of evolution, the Danish scientist Nicholas Steno found that it was possible to establish the order in which layered rocks were deposited.

...in any sequence of undisturbed layered rocks, a given bed must be older than any bed on top of it. This Principle of Superposition is fundamental to understanding the age of rocks; at any one place it indicates the relative age of the rock layers and of the fossils they contain.

If we begin at the present and examine older and older layers of rock, we will arrive at a level where no human fossils are found. If we continue backward in time, we successively come to layers where no fossils of birds are present, no mammals, no reptiles, no four-footed animals, no fishes, no shells, and no members of the animal kingdom. These concepts are summarized in the general principle called the Law of Fossil Succession . (14-15).

Geologists create a relative time scale using rock sequences and the fossils contained within these sequences. The time scale they create is based on The Law of Superposition, which states that in a regular series of sedimentary rock strata, or layers, the oldest strata will be at the bottom, and the younger strata will be on top. Danish geologist Nicolaus Steno (also called Niels Stensen) used the idea of uniformity of physical processes. Steno noted the sediment was denser than liquid or air, so it settled until it reached another solid. The newer sediment on the top layer is younger than the layer it settled upon. Since this is what happens in the world today, it should also determine how rock layers formed in the past. Crosscutting relationships are also used to determine the relative age of rocks. For instance, if a thin intrusion of granite, called a dike, cuts through a layer of limestone, the granite must be younger than the limestone.

Levin wrote:

From the time of Hutton [James Hutton (1726-1797)], leaders in the scientific community were convinced that the Earth was indeed very old, and certainly it was much older than the approximately 6000 years estimated by biblical scholars from calculations involving the ages of post-Adamite generations. (18)

Jurmain et al. wrote:

Another method of dating is flourine analysis, which only applies to bones. Bones in the earth are exposed to the seepage of groundwater that usually contains flourine. The longer a bone lies in the earth, the more flourine it will incoporate during the fossilization process. Therefore, bones deposited at the same time in the same location should contain the same amount of flourine. (234)

Tattersall wrote:

Many naturally occurring atoms (the radioactive ones) possess unstable nuclei that spontaneously "decay" to stable states of lower energy. When a radioactive "parent" atom decays, it changes to another type of atom known as the "daughter" product. The rate of decay is characteristic of the particular kind of atom involved, and is effectively independent of external conditions (98).

Levin wrote:

The rate of decay of radioactive isotopes is uniform and is not affected by changes in pressure, temperature, or the chemical environment. Therefore, once a quantity of radiocative nuclides has been incorporated into a growing mineral crystal, that quantity will begin to decay at a steady rate with a definite percentage of the radiogenic atoms undergoing decay in each increment of time. Each radioactive isotope has a particular mode of decay and a unique decay rate. (21)

Plummer et al. wrote:

Radioactive decay is the spontaneous nuclear change of isotopes with unstable nuclei. Energy is produced with radioactive decay. Emissions from radioactive elements can be detected by a Geiger counter or similar device, and, in high concentrations, can kill humans.

Nuclei of radioactive isotopes change primarily in three ways. An alpha emission is the ejection of two protons and two neutrons from a nucleus. When an alpha emission takes place the atomic number of the atom is reduced by two and its atomic mass number is reduced by four. After an alpha emission, U-238 becomes Th-234, which has an atomic number of 90. The original isotope (U-238) is referred to as the parent isotope. The new isotope (Th-234) is the daughter product.

Beta emissions involve the release of an electron from a nucleus. To understand this, we need to explain that electrons, which have virtually no mass and are usually in orbit around the nucleus, are also in the nucleus as part of a neutron. A neutron is a proton with an electron inside of it, thus it is electrically neutral. If an electron is emitted from a neutron during radioactive decay, the neutron becomes a proton and the atom’s atomic number is increased by one.

The third mode of change is electron capture, whereby a proton in the nucleus captures an orbiting electron. The proton becomes a neutron. The atom becomes a different element having an atomic number one less than its parent isotope. (189-190)

Abell wrote:

...the earth’s crust contains radioactive elements that decay slowly. Among these are potassium 40, which decays to argon 40 with a half life of 1,250 million years, rubidium 87, which decays to strontium 87 with a half life of 4,880 million years, and uranium 238, which decays through a series of elements (including radium) to lead 206 with a half life of 4,470 million years (38).

Brush wrote:

As far as is known, chemical or geological processes cannot change the relative abundances of these isotopes (60).

Monroe & Wicander wrote:

The emission of atomic particles resulting from the spontaneous decay of uranium within a material damages its crystaline structure. The damage appears as microscopic linear tracks that are visible only after etching the mineral with hydrofluoric acid. The age of the sample is determined on the basis of the number of fission tracks present and the amount of uranium the sample contains: the older the sample, the greater the number of tracks (238)

Monroe & Wicander wrote:

It is most useful for dating samples about 40,000 to 1.5 million years ago (238)

A fission-track date can be determined based on the ratio of the number of fission-tracks produced during spontaneous versus induced fission. Fission is induced through controlled irradiation with thermal neutrons of Uranium 235 (0.7 x 10 9 half-life) in a nuclear reactor. Due to the phenomenon known as annealing (fission track fading occurring as a result of exposure to high temperatures) induced fission becomes necessary in order to arrive at an accurate artifact date. With the information gained from both spontaneous and induced fission an approximate thermal age can be calculated through this equation as long as the neutron dose is known:

Age=N x Ds/Di x 6x 10 -8

N=Total Neutron dose expressed in neutrons per square cm

Ds=Observed track density for spontaneous fission

Di=Observed track density for induced fission