Explain taphonomy and provenience, and discuss how they are important to researc
ID: 98672 • Letter: E
Question
Explain taphonomy and provenience, and discuss how they are important to research looking for human ancestors. If you were trying to find the first bipedal hominid, how would these terms affect your research? What are three of the important scientific discoveries, theories, or field that PRE dated Darwin's theory of natural selection? Describe three and the person each is attributed to. How does our current understanding of the process of meiosis reinforce Mendel's laws of segregation and independent assortment? List and describe each of the four forces of evolution that we discussed in class. Give an example of each that we can observe in living populations.Explanation / Answer
1) Bipedal Hominid:
Walking upright on two legs is the trait that defines the hominid lineage: Bipedalism separated the first hominids from the rest of the four-legged apes. It took a while for anthropologists to realize this. At the turn of the 20th century, scientists thought that big brains made hominids unique. This was a reasonable conclusion since the only known hominid fossils were of brainy species–Neanderthals and Homo erectus.
While the timeline of the evolution of upright walking is well understood, why hominids took their first bipedal steps is not. In 1871, Charles Darwin offered an explanation in his book The Descent of Man: Hominids needed to walk on two legs to free up their hands. He wrote that “…the hands and arms could hardly have become perfect enough to have manufactured weapons, or to have hurled stones and spears with a true aim, as long as they were habitually used for locomotion.” One problem with this idea is that the earliest stone tools don’t show up in the archaeological record until roughly 2.5 million years ago, about 4.5 million years after bipedalism’s origin.
Taphonomy and Provinience:
In 1949, vertebrate paleontologist Ivan Yefremov, introduced the concept of taphonomy to describe the transition of animal remains from the biosphere into the lithosphere.
Taphonomic phenomena are grouped into two phases: biostratinomy; events that occur between death of the organism and the burial, and diagenesis; events that occur after the burial.Since Efremov's definition, taphonomy has expanded to include the fossilization of organic materials, inorganic materials, and both cultural and environmental influences.
This is a multidisciplinary concept and is used in slightly different contexts throughout different fields of study. Fields that employ the concept of taphonomy include:
There are five main stages of taphonomy: disarticulation, dispersal, accumulation, fossilization, and mechanical alteration.The first stage, disarticulation, occurs as the organism decays and the bones are no longer held together by the flesh and tendons of the organism. Dispersal is the separation of pieces of an organism caused by natural events (i.e. floods, scavengers etc.). Accumulation occurs when there is a buildup of organic and/or inorganic materials in one location (scavengers or human behavior). When mineral rich groundwater permeates organic materials and fills the empty spaces, a fossil is formed. The final stage of taphonomy is mechanical alteration; this is processes that physically alter the remains (e.i. Freeze-thaw, compaction, transport, burial).
Taphonomy has undergone an explosion of interest since the 1980s, with research focusing on certain areas.
Effect of Bipedal Hominid on Taphonomy:
The taphonomic pathways involved in relatively inert substances such as calcite (and to a lesser extent bone) are relatively obvious, as such body parts are stable and change little through time. However, the preservation of "soft tissue" is more interesting, as it requires more peculiar conditions. While usually only biomineralised material survives fossilisation, the preservation of soft tissue is not as rare as sometimes thought.
Both DNA and proteins are unstable, and rarely survive more than hundreds of thousands of years before degrading. Polysaccharides also have low preservation potential, unless they are highly cross-linked; this interconnection is most common in structural tissues, and renders them resistant to chemical decay. Such tissues include wood (lignin), spores and pollen (sporopollenin), the cuticles of plants (cutan) and animals, the cell walls of algae (algaenan), and potentially the polysaccharide layer of some lichens. This interconnectedness makes the chemicals less prone to chemical decay, and also means they are a poorer source of energy so less likely to be digested by scavenging organisms. After being subjected to heat and pressure, these cross-linked organic molecules typically "cook" and become kerogen or short (<17 C atoms) aliphatic/aromatic carbon molecules. Other factors affect the likelihood of preservation; for instance scleritisation renders the jaws of polychaetes more readily preserved than the chemically equivalent but non-sclerotised body cuticle.
It was thought that only tough, cuticle type soft tissue could be preserved by Burgess Shale type preservation, but an increasing number of organisms are being discovered that lack such cuticle, such as the probable chordate Pikaia and the shellless Odontogriphus.
It is a common misconception that anaerobic conditions are necessary for the preservation of soft tissue; indeed much decay is mediated by sulfate reducing bacteria which can only survive in anaerobic conditions. Anoxia does, however, reduce the probability that scavengers will disturb the dead organism, and the activity of other organisms is undoubtedly one of the leading causes of soft-tissue destruction.
Plant cuticle is more prone to preservation if it contains cutan, rather than cutin.
Plants and algae produce the most preservable compounds, which are listed according to their preservation potential by Tegellaar (see reference).
Link for Reference: https://anthropology.missouri.edu/~anthro/sites/default/files/2010%20what%20taph%20is.pdf
2) Natural selection is the differential survival and reproduction of individuals due to differences in phenotype. It is a key mechanism of evolution, the change in heritable traits of a population over time. Charles Darwin popularised the term "natural selection", and compared it with artificial selection.
a) Interestingly, Darwin and Wallace found their inspiration in economics. An English parson named Thomas Malthus published a book in 1797 called Essay on the Principle of Population in which he warned his fellow Englishmen that most policies designed to help the poor were doomed because of the relentless pressure of population growth. A nation could easily double its population in a few decades, leading to famine and misery for all.
When Darwin and Wallace read Malthus, it occurred to both of them that animals and plants should also be experiencing the same population pressure. It should take very little time for the world to be knee-deep in beetles or earthworms. But the world is not overrun with them, or any other species, because they cannot reproduce to their full potential. Many die before they become adults. They are vulnerable to droughts and cold winters and other environmental assaults. And their food supply, like that of a nation, is not infinite. Individuals must compete, albeit unconsciously, for what little food there is.
Selection of traits
In this struggle for existence, survival and reproduction do not come down to pure chance. Darwin and Wallace both realized that if an animal has some trait that helps it to withstand the elements or to breed more successfully, it may leave more offspring behind than others. On average, the trait will become more common in the following generation, and the generation after that.
As Darwin wrestled with natural selection he spent a great deal of time with pigeon breeders, learning their methods. He found their work to be an analogy for evolution. A pigeon breeder selected individual birds to reproduce in order to produce a neck ruffle. Similarly, nature unconsciously "selects" individuals better suited to surviving their local conditions. Given enough time, Darwin and Wallace argued, natural selection might produce new types of body parts, from wings to eyes.
b) The acceptance of biological evolution is an essential part of the modern scientific explanation of the natural world. Most scientists and major religions in the Western World have long since incorporated it into their understanding of nature and humanity. However, some churches still maintain that there was a special and independent creation of every species and that life forms do not change through time from generation to generation. These "creationists" often share beliefs about the Judeo-Christian Bible that were widely held, even by scientists, during the early 19th century and before.
The traditional Judeo-Christian version of creationism was strongly reinforced by James Ussher, a 17th century Anglican archbishop of Armagh in Northern Ireland. By counting the generations of the Bible and adding them to modern history, he fixed the date of creation at October 23, 4004 B.C. During Ussher's lifetime, debate focused only on the details of his calculations rather than on the approach. Dr. Charles Lightfoot of Cambridge University in England had the last word. He proclaimed that the time of creation was 9:00 A.M. on October 23, 4004 B.C.
This belief that the earth and life on it are only about 6000 years old fit neatly with the then prevalent theory of the "Great Chain of Being." This held that God created an infinite and continuous series of life forms, each one grading into the next, from simplest to most complex, and that all organisms, including humans, were created in their present form relatively recently and that they have remained unchanged since then. Given these strongly held beliefs, it is not surprising that 17th and 18th century European biology consisted mainly of the description of plants and animals as they are with virtually no attempt to explain how they got to be that way.
c) Another late 18th century closet-evolutionist was Erasmus Darwin, the grandfather of the well known 19th century naturalist, Charles Darwin. Erasmus was an English country physician, poet, and amateur scientist. He believed that evolution has occurred in living things, including humans, but he only had rather fuzzy ideas about what might be responsible for this change. He wrote of his ideas about evolution in poems and a relatively obscure two volume scientific publication entitled Zoonomia; or, the Laws of Organic Life (1794-1796). In this latter work, he also suggested that the earth and life on it must have been evolving for "millions of ages before the commencement of the history of mankind."
The first evolutionist who confidently and very publicly stated his ideas about the processes leading to biological change was a French protégé of the Comte de Buffon. He was Jean-Baptiste Chevalier de Lamarck Unfortunately, his theory about these processes was incorrect.
Lamarck believed that microscopic organisms appear spontaneously from inanimate materials and then transmute, or evolve, gradually and progressively into more complex forms through a constant striving for perfection. The ultimate product of this goal-oriented evolution was thought by Lamarck to be humans. He believed that evolution was mostly due to the inheritance of acquired characteristics as creatures adapted to their environments. That is, he believed that evolution occurs when an organism uses a body part in such a way that it is altered during its lifetime and this change is then inherited by its offspring. For example, Lamarck thought that giraffes evolved their long necks by each generation stretching further to get leaves in trees and that this change in body shape was then inherited. Likewise, he believed that wading birds, such as herons and egrets, evolved their long legs by stretching them to remain dry. Lamarck also believed that creatures could develop new organs or change the structure and function of old ones as a result of their use or disuse.
Several philosophers of the classical era, including Empedocles and his intellectual successor, the Roman poet Lucretius, expressed the idea that nature produces a huge variety of creatures, randomly, and that only those creatures that manage to provide for themselves and reproduce successfully persist. Empedocles' idea that organisms arose entirely by the incidental workings of causes such as heat and cold was criticised by Aristotle in Book II of Physics. He posited natural teleology in its place, and believed that form was achieved for a purpose, citing the regularity of heredity in species as proof. Nevertheless, he accepted in his biology that new types of animals, monstrosities (), can occur in very rare instances (Generation of Animals, Book IV).As quoted in Darwin's 1872 edition of The Origin of Species, Aristotle considered whether different forms (e.g., of teeth) might have appeared accidentally, but only the useful forms survived:
So what hinders the different parts [of the body] from having this merely accidental relation in nature? as the teeth, for example, grow by necessity, the front ones sharp, adapted for dividing, and the grinders flat, and serviceable for masticating the food; since they were not made for the sake of this, but it was the result of accident. And in like manner as to the other parts in which there appears to exist an adaptation to an end. Wheresoever, therefore, all things together (that is all the parts of one whole) happened like as if they were made for the sake of something, these were preserved, having been appropriately constituted by an internal spontaneity, and whatsoever things were not thus constituted, perished, and still perish.
But Aristotle rejected this possibility in the next paragraph, making clear that he is talking about the development of animals as embryos with the phrase "either invariably or normally come about", not the origin of species:
Yet it is impossible that this should be the true view. For teeth and all other natural things either invariably or normally come about in a given way; but of not one of the results of chance or spontaneity is this true. We do not ascribe to chance or mere coincidence the frequency of rain in winter, but frequent rain in summer we do; nor heat in the dog-days, but only if we have it in winter. If then, it is agreed that things are either the result of coincidence or for an end, and these cannot be the result of coincidence or spontaneity, it follows that they must be for an end; and that such things are all due to nature even the champions of the theory which is before us would agree. Therefore action for an end is present in things which come to be and are by nature.
3) Mendel's Law is observed in meiosis because modern scientists are fully aware of chromosomes and genes, and paired chromosomes separate during meiosis. In this way gene pairs are segregated, proving Mendel's Law of Segregation beyond doubt.
While Gregor Mendel's Law of Segregation is perhaps his most well known, the famous monk and scientist postulated three laws of inheritance. They are:
Mendel's three famous hypotheses elegantly explained genetics to a generation that was wholly ignorant of chromosomes and genes in the way that modern geneticists understand them.
The duplication of a cell results in the duplication of DNA as it divides twice to produce four reproductive cells. It is this process that is known as meiosis.
Despite the fact that modern scientists now have an infinitely greater understanding of the cell division process in all sexually-reproducing eukaryotes, Mendel's groundbreaking work ensured that he gained great fame posthumously. He is often referred to as the father of the modern science of genetics.
Mendel's Law of Segregation states that a diploid organism passes a randomly selected allele for a trait to its offspring, such that the offspring receives one allele from each parent.
Independent assortment allows the calculation of genotypic and phenotypic ratios based on the probability of individual gene combinations.
4) The four forces of evolution are: mutation, gene flow, genetic drift, and natural selection.
a) Mutation: Mutation is a random heritable change in a gene or chromosome, resulting from additions, deletions, or substitutions of nitrogen bases in the DNA sequence. Mutations may create advantageous, deleterious, or neutral traits for the organism. Eg: However, my favorite example of a beneficial mutation is called “the CCR532 mutation.” This is where a certain protein that sits on the surface of your cells is missing a small segment. Because of this deletion, the human immunodeficiency virus (HIV) is unable to attach to and enter your cells. This means that individuals with one copy of this gene are resistant to AIDS, and people with two copies of this mutation are completely immune to HIV-1. This mutation also makes people resistant to both plague and smallpox. However, since the normal version of this gene helps people resist infection by the West Nile virus, the same people who have resistance to HIV and AIDS are also have a higher risk of being infected by the West Nile virus and contracting encephalitis as a result.
b) Gene flow: Gene flow is the exchange of genetic material between two populations. Also known as admixture, gene flow works to decrease the variation between the two populations. Eg:
c) Genetic Drift: Genetic drift is the random change in allele frequency from one generation to the next. Genetic drift has much more effect in small populations, which may have an allele drift to fixation, in which all members have that allele. Eg:
d) Natural Selection: Natural selection is the process by which some organisms have a greater chance of surviving and reproducing than others due to features that are better adapted to the environment. As a result, those advantageous features are passed on at a higher frequency than less advantageous traits. Eg:
Related Questions
drjack9650@gmail.com
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.