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About Natural History

Archive for the month “June, 2012”

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.

The human brain

How often do we hear that humans only use 10% of their brain? “Imagine what humans would do if they used a greater part of their minds!”

Yet there has been a species with a larger brain than the human one, Homo neanderthalensis.

The final answer is very simple: the humans don’t use the totality of their brain because they don’t need to; the human brain is larger due to its ontogeny.

It is well known that humans do not use but approximately 10% of their brains and often one asks himself what would happen if a bigger part of the brain were used. But is this something that is possible? Sure, it could happen but it would be due to some physiological dysfunction (or some other similar phenomenon) and it wouldn’t mean that it is the way it should normally function.

The case of the human brain is a nice example for the principle of exaptation. During the evolution of the humanoids,  Homo neanderthalensis was the one species that had a larger brain than the one of Homo sapiens (humans). The reason is very simple: the brain was larger because it could. Human brains are quite big as well, for the embryological reason that it was able to grow more. This means that we do not actually need more than the 3/4 of our brain, we just have it because during the early ontogenesis, the nervous tissue of the region of the head gets larger than the one of other animals. It is a passive process that does not consist of a specific adaptation or a need. Indeed, it is quite useless to have such a large brain since humans -and much more neanderthals- do not even use half of it. But the organism is not able to find a way to use it from a physiological and histological point of view.

The large brain that we are so proud of is therefore something that we only have a partial use for, and from the moment that we know that, the myth that we could be much smarter if we could use more than 10% of this organ seems irrelevant.

The use of logics in science

The goal of scientists is to retrieve data and emit hypotheses on a question they ask themselves. They seek the truth about something using logics to guide them through their work. Taking into consideration the facts, the data, they try to treat it correctly, in an objective manner, and have results that reflect the real phenomenon. But how well does this work? There are some examples that reflect this idea, I’m going to talk about the one that I know best, having encountered it during my studies.

There is this known controversy of mathematicians and physicists against evolutionary biologists and palaeontologists: the first two fail to understand how it is possible for organisms with survival rates close to zero to actually survive. Following the laws of probabilities it is indeed impossible for living beings (such as the horse or even humans to take as some popular examples) to survive in the struggle for life. Yet they still exist and others, with better mathematical survival-probabilities, disappear very rapidly. Should these scientists think a bit outside the box, would they understand how evolution works; it is not about what we should find, nature -and life- does not always work that way.

But this is only an example of how scientific logic works. How can we be sure that we are open-minded or that we even can be right in the treatment of data?

In the book of Stephen Jay Gould “Time’s arrow, time’s cycle”, the author refers to F. Engels saying how it is impossible to think out of the trends and the ideas of our times. This is just another point to the fact that scientists do not know everything, as much as they’d like to think they do (I admit that I should include myself in this category…).

So can scientists be certain to explore a problem from every possible aspect?

Understanding the history of the earth before the discovery of tectonics

While reading S.J. Gould’s “Time’s arrow, time’s cycle  – Myth and metaphore in the Discovery of Geological Time“, I noticed a few things.

In the first part of the book, Gould describes the ideas on the -brief- history of the earth as seen by Thomas Burnett (late 17th century). It gets far more interesting, as far as the modern thought is concerned, in the second part of the book. There, we find the work of James Hutton, a scottish geologist of the 18th century. He had made very accurate and original observations in his homeland (discordances, discontinuities…). He tried to explain them but in vain. How would it be possible to understand a discontinuity, sediment orientation, etc. without having any knowledge of a mechanism that would allow change of the surface of the earth? How is it possible to study and understand the history of the earth without using tectonics?

The third part of the book is dedicated to the work of Charles Lyell (19th century). There again, we see that he observes faults and other landscape results of earthquakes. As much as Lyell’s work is significant to Geology, the mechanism responsible for some of his observations was still unknown; raising the same problems of the changes of the surface of the earth. All the theories preceding the discovery of tectonics were speculative even if the scientists tried to be realistic.

If we want to do a parallel with evolutionary biology, I remember the famous quote of Theodosius Dobzhansky: “Nothing makes sense in Biology except in the light of Evolution”. Well, I think that something similar can be said about tectonics: “Nothing makes sense in Geology, except in the light of Tectonics”. Therefore, Tectonics is to Geology what Evolution is to Biology.

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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