(Sail) Study Help Only On the voyage of the Beagle (1831-1836) Darwin collected and described thousands of animals and plants. In South America he observed the adaptations of organisms to a variety of habitat from jungle to grassland to mountain habitats. In the temperate regions the species resembled more closely the species of the tropical regions of South America rather than the corresponding species of the temperate regions of Europe. For example, in the grasslands of Argentina there are no rabbits, however, there are rodents that resemble rabbits; these rodents are unrelated to European rabbits but are similar to other rodents in South America. Moreover, the fossils in South America are dissimilar to European fossils but have similarities with extant (i.e.
currently living) plants and animals in South America. Darwin was particularly intrigued by the finches on the islands of Galapagos which are located approximately 500 miles from the mainland of South America. These finches, although unique to these islands, were clearly related to mainland species. There were 14 different species or genera of Galapagos Finch and their bills were adapted for particular diets. Darwin amassed these and other data including observations on variability in domestic animals (for example, dogs) which had been brought about by generations of selective breeding.
As well as drawing on his own observations, Darwin drew from the work of Linnaeus, Cuvier, Hutton, Lyell, Malthus and Lamarck. In the hierarchial classificatory system of Linnaeus there is a tacit acknowledgement of relatedness, for example, species belonging to one genus have more in common with each other than they do with species belonging to another genus. Linnaeus was a creationist – as evidenced by his egotistical proclamation God creates, Linnaeus arranges. Cuvier, also a creationist, was a comparative morphologist (he described the similarity/dissimilarity in anatomy of diverse animals). Cuvier founded the science of paleontology and described the differences between the fossil flora and fauna in different strata of rock: he observed that the more recent strata had fossils that more closely resembled extant organisms. Cuvier believed that the discontinuities between fossils in different strata were brought about by catastrophes such as floods which caused the extinction of many species living at a particular time.
This interpretation of earth’s history is termed catastrophism and was also held by many contemporary geologists. By contrast, Hutton and subsequently Lyell held that geological processes are slow and subtle but that over prolonged periods of time (millions of years) these can lead to major changes; implicit in this viewpoint is an age for the earth radically different from the 6,000 years of the biblical creationists. Other key influences on Darwin were Malthus who had concluded that war and famine were inevitable as the human population grew more rapidly than available resources, and Lamarck who had proposed a theory of evolution based on a continuous process of gradual modification due to acquired characteristics. Both Darwin and Wallace brought together a multitude of facts including the geographical distribution of organisms, comparative morphology of living organisms and their fossil precursors. They postulated that long-term environmental changes including movement of land masses and changes in climate could have served in the process of natural selection over many generations with the result that diverse species arose from ancestral types.
Darwin termed this descent with modification (the term evolution was introduced later, as was the tautology survival of the fittest). Darwin’s ideas can be summarized in his own words from The Origin of Species: As many more individuals of each species are born than can possibly survive, and as consequently there is a frequently recurring struggle for existence, it follows that any being, if it vary in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of survival and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form. In assessing the contribution of Darwin and Wallace it should be noted that the key role in heredity of the nucleus, chromosomes and DNA were not demonstrated until 1892, 1903, 1943, respectively. Also, the Darwin-Wallace theory of evolution was developed without an appreciation of Mendel’s work on inheritance (ironically, Mendel had written to Darwin with his ideas but Darwin overlooked their significance). Subsequent studies have drawn closely together the fields of evolution, genetics and molecular biology.
For example, the inherited disease of sickle-cell anemia is caused by a minor change in DNA which causes a minor change in the hemoglobin protein of red blood cells. Individuals with two sickle-cell genes suffer sickness and may die, but those individuals with one sickle-cell gene have a greater resistance to malaria. Thus it can be seen that this gene may have a survival advantage for Africans in malarial areas. Not all changes in DNA produce such dramatic effects in proteins and in the individuals who possess those proteins. Some changes in DNA cause only minor effects or may have no tangible effects on the organism.
By systematically comparing the DNA of different organisms it is possible to determine the degree of similarity/dissimilarity between organisms and thus determine phylogenetic (i.e., evolutionary) relationships between them. For example, in the case of human phylogeny both skeletal structure (comparative morphology) and gene structure (molecular biology) indicate that humans are more closely related to chimpanzees than to New World monkeys. He also wrote The Descent Of Man. In 1974, a discovery was made that dramatically popularized the issue of human evolution. In Hadar, Ethiopia, Dr.
Donald Johanson unearthed a strange primate skeleton. Although it would be four years before Australopithecus afarensis was declared a new species, A.L 288-1 — better known as Lucy — soon became a cultural icon. [photo of Lucy specimen] Johanson had been searching for Lucy or something like her for almost a year when the skeleton came to light. In 1973, he and another paleontologist had found a knee joint they could not classify washed out of a river in Hadar. Suspecting that other members of the same species were buried in the area, Johanson began to dig. Lucy was the result. Several things struck Johanson about his find.
First, it appeared to be of the same species as the 1973 knee joint. Second, the remains were clearly female. Finally — and this is by far Johanson’s most important claim — he believed that this primate had walked upright. As soon as the news hit the presses, Lucy became a superstar. Creationists quickly declared that Lucy was not a hominid, but only an ape. Allegations were made that Johanson had tampered with the evidence in order to become famous. Evolutionists argued that Lucy was a perfect example of a transitional hominid, closely related to both humans and an ancient, undiscovered ancestor of boths humans and modern apes. What Was Lucy? More than two decades after her discovery, debate still smoulders over Lucy’s identity.
Was Australopithecus afarensis truly an ancestral human? Or were they merely apes, now long extinct? Although Lucy is by far the best-known example of Australopithecus afarensis, about 300 separate individuals have been found since 1973. Using argon-argon dating and other techniques rejected by Creationists as inaccurate, Evolutionists have determined ages of between 3 and 4 million years for Australopithecus afarensis remains. The Lucy specimen herself has been dated at 3.2 million years. Creationists say these methods are arbitrary and wrong. Evolutionists maintain they are accurate.
Modern opinions about Australopithecus afarensis vary. Evolutionists now speculate that Lucy and her species were ancient relatives of modern humans, although not necessarily direct ancestors. According to the evolutionary perspective, Lucy could be considered a sort of great-aunt rather than a great-grandmother to modern humanity. Evolutionists point to anatomical evidence in the afarensids that indicates Lucy’s species was capable of walking upright in a manner unlike any modern apes. Evolutionists view this as the first step towards full humanity. Creationists, on the other hand, believe Lucy has been misinterpreted. They insist that Lucy was just another ape, and that her species was almost identical to the chimpanzees of today.
Although they agree that Lucy may have walked upright now and then, they point out that modern chimpanzees are also capable of an occasional upright stroll. Creationists emphasize the ape-like features of Australopithecus afarensis. They feel there is little or no evidence that the species was a product of evolution. What is the truth about Lucy? That is for you to decide. The Lucy Test was developed as a springboard for people interested in the topic of human evolution.
I hope you will pursue this topic further and research it to your heart’s content. Take The Lucy Test. Your results may surprise you. What are some of the features that make us different. There are lots of features that make us unique.
We are the only species that has an opposable thumb. We are also the only ones that are able to walk upright. Why do I think people have a hard time accepting human evolution. I think people have trouble accepting human evolution for many reasons. I think they are afraid of what they dont want to accept not to mention damn stubborn. I also think that they want to belong to some great force like they think is there god.
I personally dont believe in god. I accept the concept. History Essays.