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==What about now?== | ==What about now?== | ||
Nowadays there are evidences, which shows that humans had involved through the time. Let's take the example of people, who are able to digest lactose. Of course, every human are born with the capacity to digest lactose, a sugar which is in the milk, because that is the main food of an infant. But after a certain age, the ability to digest lactose disappeared, because we stop producing lactase, an enzyme which breaks down the lactose in order to absorb it more easily. This disappearance can be caused by the natural selection, in fact our ancestors did not have any source of mil, so producing the lactase, an enzyme which was not needed was useless. | Nowadays there are evidences, which shows that humans had involved through the time. Let's take the example of people, who are able to digest lactose. Of course, every human are born with the capacity to digest lactose, a sugar which is in the milk, because that is the main food of an infant. But after a certain age, the ability to digest lactose disappeared, because we stop producing lactase, an enzyme which breaks down the lactose in order to absorb it more easily. This disappearance can be caused by the natural selection, in fact our ancestors did not have any source of mil, so producing the lactase, an enzyme which was not needed was useless. But in some population, mainly the one who raise cows, the ''pastoralists'' , there are people who go on to produce this enzyme during their adulthood, this production gives them a rich source of nutrition not available to the others. The persistence of lactase depends on a simple modification in the DNA. | ||
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*retour à [[Evolution_3BIbDF10-11_2011/12]]<br> | *retour à [[Evolution_3BIbDF10-11_2011/12]]<br> | ||
*retour à [[Accueil]] | *retour à [[Accueil]] | ||
Version du 26 avril 2012 à 09:02
WHAT ABOUT US?
What is Darwin's theory of Evolution?
The theory of Darwin suggested that all living creatures are related to one another. The fishes, the birds, the mammals, the plants, and so on all have a common ancestor. There might just have been modifications and mutations that came along the long process of evolution.--KimberlyR 16 mars 2012 à 15:43 (CET)
Where were the first Humans found?
Darwin supposed that the early humans first lived in Africa, then migrated out of Afica and then into Asia about 2 million years ago. And then eventually reached Europe.--KimberlyR 16 mars 2012 à 15:43 (CET)
What are the human's ancestors?
Darwin thought that homosapians came from Africa because our closest relatives, gorillas and chimpanzees are found there.--KimberlyR 16 mars 2012 à 16:21 (CET) But the author is sceptic about it, because there are no concrete evidences, no fossils to prove that.--KimberlyR 16 mars 2012 à 16:21 (CET)
Darwin affirmed that humans had evolved from apes. He said that the mutation of the apelike species, which included the higher mental faculties of humans could be explain by the natural selection...
Our common ancestor
Who discovered the first fossil ancestors?
In 1871, the physician Eugene Dubois had discoverd in Java a human fossil. The skull was more robust than humans and the size of the brain was smaller. This fossil was too humanlike to be the missing link between us and apes. But distressed by the opposition between religion and science, Dubois decided to buried the fossil of Homo erectusin his house and he hid it for three decades.
In 1924, Dart a professor of anatomy at the University of Witwatersrand, but also an amateur of anthropology had discovered one of the greatest fossil. While he was at a wedding, a postman brought him two boxes containing bones fragment. When he oppened the boxes, he discovered a replica of a brain three time larger than a baboon's brain and bigger than a brain of an adult chimpanzee. The size of this replica of the brain was not big enough to be a primitive man, but it was much bigger than ape's brain. Dart is the one who discovered the first Australopithecus africanus.
Australopithecus africanus
This species is a fossil hominid, wich lived
Donald Johanson, a paleoanthropologist from America, made the decisive find by discovering "Lucy" in the Afar region of Ethopia. On November 1974, he found the bones of a single indiviual, Lucy was a female aged between twenty and thirty years old, measuring three and a half feet ang weighing around sixty pounds and the most important thing, she was a biped. Johanson discovered a new species: the Austrlopithecus afarensis
Australopithecus afarensis
The Australopithecus afarensiswas a biped hominid, which lived in Africa between 3 and 4 million years ago. It had an apelike head with a chimpsized brain, but its skull showed similarities with humans. Its tooth row was semiparabolic and the canine teeth were reduced.The arms were longer than humanlike, but shorter that apelike, and their fingers were curved, wich shows that Austrlopithecus afarensis had spent some time in the trees. This species shows perfectly the transition between apes and humans: the head and the neck were apelike; in the middle, it was a "mixture" between humans and apes; and from the wais down, this species is biped, almost like modern human. The Austrlopithecus afarensis shows a fact, which was agains the convention of the time: the human posture evolved long before human's big brain.
definitively not enough... Wake you up!--Pierre.brawand 28 mars 2012 à 14:05 (CEST)
How different are Humans from Chimpanzees?
In 1975, Allan Wilson and Mary-Claire King at the University of California, made an experiment to try to find out what differentiates us from our closest relatives, apes. They took humans and chimpanzees protein sequence, and compared them. They then found out that humans and chimpanzees, aren't actually that different, because the protein sequence only differed by only about one percent. After some time, with some more recent researches, that difference rose to about 1.5 percent. But that still stayed relatively low, which shows a great similarity between both species. Wilson and King thought that those changes only rested on a few gene mutations. But actually, what those two researchers found in 1975 is not totally accurate. Because the reason why humans and chimps are so different, is much more complicated. We can not rely totally on that 1.5 percent diffrence.. Changes aren't only present in "proteins produced my genes, but also in the presence or absence of genes, the number of gene copies, and when and where genes are expressed during development." -à devolopper cette partie... --KimberlyR 30 mars 2012 à 16:35 (CEST)
What are the different races?
What about now?
Nowadays there are evidences, which shows that humans had involved through the time. Let's take the example of people, who are able to digest lactose. Of course, every human are born with the capacity to digest lactose, a sugar which is in the milk, because that is the main food of an infant. But after a certain age, the ability to digest lactose disappeared, because we stop producing lactase, an enzyme which breaks down the lactose in order to absorb it more easily. This disappearance can be caused by the natural selection, in fact our ancestors did not have any source of mil, so producing the lactase, an enzyme which was not needed was useless. But in some population, mainly the one who raise cows, the pastoralists , there are people who go on to produce this enzyme during their adulthood, this production gives them a rich source of nutrition not available to the others. The persistence of lactase depends on a simple modification in the DNA.
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- retour à Accueil