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Archive for the tag “evolution”

Evolution, in a nutshell

This is a nice video that explains how Evolution works. It is very summarizing of course, since it is eleven minutes long, but it is very well explained and the animation helps visualize the mechanisms that allow Evolution to take place.

This is Charles Lyell

Why should we talk about Charls Lyell? Well he was one of the most important scientists that drew attention to his discipline as well as a great thinker of his time. Unfortunately, most of the time we are told that he influenced Charles Darwin, A. R. Wallace, T. H. Huxley and R. I. Murchison, but how and why?

charles-lyell-5

One thing Lyell (1797 – 1875) is known for is that he wrote the book that really founded modern Geology: “Principles of Geology“. But how did he get to be interested in Geology in the first place?
He studied in Oxford, graduated around 1820 and started working as lawyer. During this time he travelled around England, thus being able to observe geological formations. He was so fascinated by geology that even during his honeymoon in Switzerland and Italy, he and his wife (daughter of a member of the Geological Society of London) did a geological tour of the area.

His best known work is the book “Principles of Geology” which is itself known not only because it is important, but also for inspiring Darwin in his work.

lyellprinciplesgeology.1

First Edition of the “Principles of Geology”

He had the vision and the ability to think a bit beyond a simple landscape, and, having in mind the works of James Hutton, was able to find an explanation for the deposition of geological layers. The central argument of the Principles is that of uniformitarism, and in his own words he made “an attempt to explain the former changes of the Earth’s surface by reference to causes now in operation”. And this is what makes his works and way of thinking absolutely modern.
Another important part of his work was in Stratigraphy – I believe this is his most important contribution to Geology. He travelled through Europe, studied and described many formations and he kept updating his Principles with the latest works until the 12th edition of 1875.

His interest and work on Evolution is also something we should remember: he endorsed both Darwin and Wallace in their works, as he was already a well respected scientist in the United Kingdom.

He died two years after his wife, in 1875, and was buried in Westminster Abbey.

Shells and Bones?

Could anyone imagine that a world in which no skeletal parts would exist could replace the world as we know it?
Well it already has existed, in fact this was the world during the whole of the Precambrian.

Do we not take all the skeletal parts for granted? Most of the time, the animals that surround us, that we notice the most, are composed of one sort of skeleton or another. Cats, dogs, snails, chickens… all have a kind of skeleton. But how often to we think about why do we even have hard mineralized bones? How are bones and shells made? Why do not all animals have it?

During the last couple of decades research on the topic of bio-mineralizations, or how do organisms create hard parts, has taken off. The major axes of interest are the mechanics and the genetic signal and control of the elaboration of skeletal parts in animals, the functional history of these genes etc.

Before the Cambrian, many animals existed as attests the famous Ediacara fauna, and it is believed that many more must have existed but we have no fossils to trace. The main reason for this is that these creatures did not possess skeletal elements, therefore making the fossilisation process extremely unlikely. The other consequence is that it is very difficult to assess the biodiversity of the Precambrian. And one very interesting problem arises: the Cambrian explosion cannot be seen as a real explosion of life, a moment of rapid diversification of life.
Indeed, for a long period of time – and today still, the Cambrian era was considered as the time when biodiversity increased considerably in a very short time lapse, simultaneously with the first appearance of skeletal parts. For this, it is only logical to believe that the genes must have existed previously to the “explosion” itself. Questions rise as to the true nature of the beginning of the Cambrian; it seems to be more of an extinction crisis: the organisms that weren’t able to keep up with the new technological advancement of the skeletal parts, and the first known predation advancements that also occurred during the Cambrian.

© SWEDISH MUSEUM OF NATURAL HISTORY. PHOTOS: STEFAN BENGTSON.

Early tube-dwelling Cambrian animals. © SWEDISH MUSEUM OF NATURAL HISTORY. PHOTOS: STEFAN BENGTSON.

Many things we do take for granted but do not stop to think about why and how they exist, and yet so many questions and mysteries lie in their study.

Wallace

http://www.morningstaronline.co.uk/content/view/full/133310.

Cuckoo: evolutionary mystery uncovered

A remarkable bird shows how many things were impossible to understand before the Evolutionary theory was fomulated. A few observations that puzzeled naturalists for a long time in the most well known “evolutionary cheat”.

Lamarckism and the scala naturæ

This is something that I have happened to notice a few times: how the ideas of lamarckism and the great chain of beings (scala naturæ) are still present in the minds of many people.

It seems a bit outdated, but these are two ideas that are quite popular among those who do believe in Evolution. As far as lamarckism is concerned, very often it is confused with the principles of natural selection. Indeed, it is believed that mutations happen and that they are the ones  that produce changes within species. But the mechanisms of how the mutations work and how they intervene are not well known. Here lies the global difference between Lamarck’s evolution and Darwin’s evolution (where the mutations occur in the germinal cells). Also, there is the belief that characters appear because there is a need for them by the organisms. The fact that characters appear hazardously and are retained or rejected by natural selection is not well grasped, which brings us to the same confusion of how mutations function.

Now, about the “Great Chain of Being” or scala naturæ. This is another type of misunderstanding of the diversity of life and man’s place in it. Humans often believe that they are superior to all of the other animals, and to plants as well (the french botanist Francis Hallé http://fr.wikipedia.org/wiki/Francis_Hall%C3%A9 has described how plants are very complex organisms, proving that such an idea is simply false). Therefore, the scala naturæ makes sense, since it  describes the succession of organisms that lead to the complexity and the perfection of humans. Other concepts accompany this idea: lower/superior animals, lower/superior plants… These ideas only make sense in the larger frame of the chain of being.

The true understanding of the science of Evolution, needs the general understanding of genetics, biochemistry and some knowledge of the diversity of living organisms on Earth. Perhaps this is the cause for these misunderstandings and misinterpretations that lead to the persistence of these ideas in today’s popular evolutionist belief.

http://www.alfredwallace.org/

http://www.alfredwallace.org/

The biography of the great naturalist of the 19th century. A very interesting website about the life and work of Alfred Russel Wallace.

George Gaylord Simpson.

G. G. Simpson is one of the greatest and most influential palaeontologists of the 20th century for several reasons: the evolution of horses is a very well known example of his work, as well as his contribution on the modern evolutionary synthesis.

I remember though, during palaeontology and/or evolution classes, the professors telling us repeatedly that we had to know and remember Simpson, but without ever telling us precisely why. It was only after a while that I came across one of his books in a little naturalistic bookstore right beside the University of Jussieu. It was an old book, published in French in 1951: “The meaning of evolution”, it was originally published in English in 1949.

First of all it is quite curious and pleasant to see that so shortly after the end of the Second World War the interest in palaeontology and evolution was such that this book was translated and published.

More importantly, while reading it, I realized that almost all of its content was the bigger part of everything that is taught in palaeontology classes (the principle of vicarience, speciation, migrations, the orientation of evolution and its trends, radiations, evolutionary factors and their impacts, …) . Only then did I understand his contribution to modern palaeontology, the importance of his life’s work, and how he established all the bases in the paleontological studies.

Evolution by Alfred Russel Wallace

Yes, in our minds Evolution = Charles Darwin. But if we lived in the 19th century things would be slightly different.

In 1855 Alfred Russel Wallace had not only been convinced of the existence of natural selection but he strongly believed that it was a driving force in the process of evolution. Like most naturalists of his time, he traveled first in Brazil – on board of the Mischief – along with entomologist Henry Bates. What is really interesting about this naturalist is that he deliberately planned his work hoping to find evidence that would support the evolutionary theory, which by the way was called “the transmutation of species” at that time.

It does seem a bit odd that A. R. Wallace is largely unknown and it was very nice to see that a team of the Natural History Museum of London is currently working on his collections of insects and other specimens, as well as on his letters and notes.

Wallace had a bigger interest for studying populations and observing more insects and plants. Maybe this is due to his fellow friends with whom he collected all of his specimens, unlike Charles Darwin who traveled by himself. The fundamental ecological and biogeographical perspectives that Wallace gave to the evolutionary theory along with his observations that led to the “discovery” of natural selection make him a fundamentally important naturalist in evolutionary sciences and maybe another person for creationists to blame…

Evolutionary Epigenetism: why do we still mention it?

I was at the lab (UOA) looking for bibliography on the Pliocene of Greece, when  I found a copy of a rather old book on Evolutionary Paleontology (“Paléontologie Evolutive” of Jean Roger, 1976). It caught my attention, not only because it is one of my favorite subjects, but also because from what I’ve seen, Evolutionary Paleontology is and has been taught in different ways.

In the summary I found a lot of things that I’ve learned in relevant lectures, but there was one or two things that really got my attention. So here is my question: why do we still talk about evolutionary epigenetics?

Yes, in genetics classes we’ve learned that there are modifications of the genes after they’re transcripted into mRNA, and we’ve been told that this is one epigenetic mechanism. But, what is the relation between this and the evolutionary theories of epigenetics?

The book enlightened one first point, in the chapter on the mechanisms of evolution there is one part about the epigenetic theory. The author quotes P.P. Grassié: “an evolutionary necessity is the acquisition of new genes”. And later on we find another quote by S. Ohno (1970): “natural selection, much like a “policeman” is extremely conservative; if evolution depended only on this, from Bacteria could be obtained only many other forms of Bacteria. The creation of Metazoans, Fish, Mammals would be almost impossible without the creation of new genes.” No further explanation by the author. This is epigenetic evolution. The lack of further knowledge on genetics, genes duplication, the fact that natural selection is able to produce new genes, horizontal transfer etc. generated this idea that there are other mechanisms that produce diversity, independent from Darwin’s evolutionary theory. It does seem a little like an ensemble of speculations, because there is no specific proposition of a precise epigenetic mechanism. Also, and very wisely, the author does not take any sides, and waits for further research for an answer on the importance and the existance of such processes.

Modern epigenetics do not have the same evolutionary dimension.

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