“It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change.” -Charles Darwin
Charles Darwin’s Theory of Evolution:
All life is related and has descended from a common ancestor: birds and bananas, fishes and flowers, humans and kangaroos--all related to each other. “ Descent and modification” means that simplistic ancestors evolved to more complex creatures over time naturally. Then there is “natural selection” which is the process where random genetic mutations aid survival. It is basically survival of the fittest. Through time and space, species evolved due to genetic mutations, environmental change, different climates, lack of food sources, and etc. Over time, beneficial mutations accumulate and the result is an entirely different organism.
Darwin’s Theory of Evolution follows three fundamental ideas:
1) Species: Population or group capable of interbreeding and producing fertile offspring. For example “deer” refers to a family of 34 species that include Eld’s Deer, Red Deer, Wapiti, etc.
2) All organisms share common ancestors with other organisms.
3) Evolutionary change is slow.
The process of Natural Selection:
1. Variation: Organisms show variation in appearance and behavior while others show very little to no variation among individuals. For example, number of eyes in vertebrates.
2. Inheritance: Some traits are consistently passed on from parent to offspring. Some traits are heritable while other traits are influenced by the environment and shows weak heritability.
3. High rate of population growth: High population growth may lead to a struggle for resources. Each generation experiences high mortality.
4. Differential survival and reproduction: Traits that are passed on for survival.
PROOF OF DARWINS THEORY:
Homologous structures:
Forelimbs of human, bat, penguin and the alligator share anatomical traits.
The humerus, radius, ulna in each forelimb of these animals are similar to the human skeletal structure. They also derived from the same structures in the embryo. Even though these animals look different from each other their homologous structures shows that they are quite similar. Homologous structure are structures that are embryologically similar, but have different functions.
Vestigial Organs:
Vestigiality describes homologous characters of organisms that has lost their original functions in species through evolution. Humans have a vestigial organ. It is the tailbone at the end of the spine that has no useful functions whatsoever. Vestigial organs are often homologous organs to organs that are useful in other species. For example, ostrich and chickens have wings but they cannot fly.
Anatomical atavisms:
According to The Talk Origins Archive, atavismis the reappearance of a lost character specific to a remote evolutionary ancestor and not observed in the parents or recent ancestors of the organisms displaying the atavistic character. Atavisms have several features.
1) presence in the adult stages of life
2) absence in parents or recent ancestors
3) extreme rarity in a population
Hypothetical example: If a mutant horse had gills, it could be considered a atavism because the horse has something (gills) that belongs to Taxa (e.g fish) to which horses do not belong.
Some examples of Anatomical Atavisms:
1) Whales: According to the standard phylogenetic tree , whales use to be terrestrial mammals with legs and feet. There has been cases where whales have been found with hind limbs.
2) Another example is an atavistic tail found in a six year old girl.
X-ray image of an atavistic tail found in a six-year old girl. A radiogram of the sacral region of a six-year old girl with an atavistic tail. The tail was perfectly midline and protruded form the lower back as a soft appendage. The five normal sacral vertebrae are indicated in light blue and numbered; the three coccygeal tail vertebrae are indicated in light yellow. The entire coccyx (usually three or four tiny fused vertebrae) is normally the same size as the fifth sacral vertebrae. In this same study, the surgeons reported two other cases of an atavistic human tail, one with three tail vertebrae, one with five. All were benign, and only one was surgically "corrected" for cosmetic reasons (image reproduced from Bar-Maor et al. 1980,
Humans shared a common ancestor with chimpanzees 8 million years ago, whales, 15 million years ago, and kangaroo over 150 million years ago. Our shared ancestry illustrates our similarities with these organisms. We inherited certain traits from these common ancestors.
<--------/----------/----------/-------->
150 mya 15 mya 8 mya
Kangaroo Whales Chimpanzees
Chimpanzees:
Chimpanzees and humans shared a common ancestor with chimpanzees 8 million years ago. Around 6 million years, the divergence of the lineage began and started a specie, modern humans. This speciation started an evolutionary process that made chimpanzees to become the most closest living cousin.
There is a debate about whether humans evolved in Africa which is the out of Africa hypothesis or whether humans arose simultaneously in many different places in the world after our ancestors moved out of Africa (multi-regional hypothesis). Though there is a controversy about where humans evolved, there is no disagreement that the common ancestor of both the chimpanzees and modern humans lived in Africa.
What led to this divergence?
One hypothesis is that part of the population of the common ancestor became geographically isolated from the rest of the population over a long period of time. Geographic isolation would prevent the process of gene flow from one population to the other. This caused two evolutionary paths that can no longer interbreed.
Another hypothesis is mutation that prevent interbreeding between parts of the population that have mutation and parts that do not.
Some characteristics that we share with chimpanzees are genes and skeletal structure. According to Dr. Daniel Geschwind, “We share more than 95 percent of our genetic blueprint with chimps. What sets us apart from chimps are our brains: homo sapiens means ‘the knowing man’.”
This visual timeline shows the stages of development of human from chimpanzees. It explains certain traits and characteristics that has been passed on through evolution.
So you can see here that both chimpanzees and humans have the same skeletal structure.
Whales:
Humans shared a common ancestor with whales 15 million years ago. Whales share many similar traits to humans. They are social and intelligent creatures which allow them to use tools, cooperate and have intricate communication skills. Two whale species and humans are the only ones that go through menopause. No other animal develops menopause. Scientists found that several cetacean species including whales have a type of neutron in their brains that is also found in humans and apes. There was also a presence of spindle cells in the humpback whale cortex which is only encountered in the human and ape brain. Spindle cells allows them to feel emotions and interact socially. But it seems like whales developed spindle cells far longer than humans. It appeared in apes about 15 million years ago while whales developed them as long as 30 million years ago.
Kangaroo:
Humans shared a common ancestor with kangaroo 150 million years ago. According to Australian researchers, Australia’s kangaroo are genetically similar to humans. They have, for the first time mapped the genetic code of the kangaroo and found that much of it was very similar to human genome.
Director Jenny Graves says “ There are a few differences, we have a few more of this, a few less of that, but they are the same genes and a lot of them are in the same order. Kangaroos are hugely informative about what we were like 150 million years ago”.
Horses:
Modern humans also shared a common ancestor with horses.
They are both a part of the kingdom animalia. They are both from the phylum chordata and they are both in the class of mammalia. Well sure, all animals fall into those three classifications. What other characteristics do they share.
You may not now this but early man, Ardipithicus Ramidus, was an herbavore. Ardipithicus ramidus ventured out of the forest and into the grasslands, perhaps to escape the omnivorous Ardipithicus Ramapithicus. The grasses and plants there were tougher than the softer leaves and fruits of the forest. As ardi. rami. developed into Australopithecus Afarensis her jaws had become stronger and molars more developed for the tougher plants of the plains.
The first horse, Hyracotherium, was also a forest dweller. It also grazed on soft plants and fruits and had more of a dog-like body structure with four toes on it’s front and three toes on it’s hind legs that were padded. Towards the end of the of the Eocene it too moved out into the plains and developed more grinding molars to deal with the tougher grasses and plants.
Both evolved from forest life to life on the plains which required a better apparatus for chewing the tough plants of the plains. Another common trait horses and humans share is hair. Most animals have fur, such as cats and dogs. Though some dogs, such as poodles have hair, all breeds of horses have hair. Based on homologies, it is concluded that horses and humans did share a common ancestor. While the first horses appeared around 54 my and the first humanoids only around 5my, their early transitions were similar.
In terms of bone structure, horses never did have five toes, but we share the same basic arm and leg structures.
As you can see from the above image, the ulna and radius of the horse has fused together ( an adaptation specialized for running and jumping which were necessary for escape from predators). The radius and ulna of humans remained split allowing for rotation which was required for the use of manipulating tools. Though our basic bone structures remain similar, right down to our useless tail, they adapted to our individual requirements for survival.
They are both a part of the kingdom animalia. They are both from the phylum chordata and they are both in the class of mammalia. Well sure, all animals fall into those three classifications. What other characteristics do they share.
You may not now this but early man, Ardipithicus Ramidus, was an herbavore. Ardipithicus ramidus ventured out of the forest and into the grasslands, perhaps to escape the omnivorous Ardipithicus Ramapithicus. The grasses and plants there were tougher than the softer leaves and fruits of the forest. As ardi. rami. developed into Australopithecus Afarensis her jaws had become stronger and molars more developed for the tougher plants of the plains.
The first horse, Hyracotherium, was also a forest dweller. It also grazed on soft plants and fruits and had more of a dog-like body structure with four toes on it’s front and three toes on it’s hind legs that were padded. Towards the end of the of the Eocene it too moved out into the plains and developed more grinding molars to deal with the tougher grasses and plants.
Both evolved from forest life to life on the plains which required a better apparatus for chewing the tough plants of the plains. Another common trait horses and humans share is hair. Most animals have fur, such as cats and dogs. Though some dogs, such as poodles have hair, all breeds of horses have hair. Based on homologies, it is concluded that horses and humans did share a common ancestor. While the first horses appeared around 54 my and the first humanoids only around 5my, their early transitions were similar.
In terms of bone structure, horses never did have five toes, but we share the same basic arm and leg structures.
As you can see from the above image, the ulna and radius of the horse has fused together ( an adaptation specialized for running and jumping which were necessary for escape from predators). The radius and ulna of humans remained split allowing for rotation which was required for the use of manipulating tools. Though our basic bone structures remain similar, right down to our useless tail, they adapted to our individual requirements for survival.
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http://www.onelife.com/evolve/manev.html#C
Http://www.talkorigins.org/faqs/horses evol.html
http://accessscience.com/content/taxonomy/679400
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