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Posts Tagged ‘punctuated equilibrium

“For you formed my inward parts; you knitted me together in my mother’s womb. I praise you, for I am fearfully and wonderfully made.”*…

DNA is indisputably important to biological development. But, Alfonso Martinez Arias argues, far from being a blueprint for an organism, genes are mere tools used by life’s true expert builders: cells…

… Over the past century, scientists have discovered a material explanation for the source of life, one that needs no divine intervention and provides a thread across eons of time for all beings that exist or have ever existed: deoxyribonucleic acid — DNA. While there is little doubt that genes have something to do with what we are and how we come to be, it is difficult to answer precisely the question of what their exact role in all of this is.

A closer look at how genes work and what they can accomplish, compared to what they are said to achieve, casts doubt on the assertion that the genome in particular contains an “operating manual” for us or any other living creature. When it comes to the creation of organisms, we’ve overlooked — or, more accurately, forgotten — another force. The origin and power of that force are cells.

What makes you and me individual human beings is not a unique set of DNA but instead a unique organization of cells and their activities…

A fascinating essay, adapted from Martinez Arias’ forthcoming book, The Master Builder- How the New Science of the Cell Is Rewriting the Story of Life: “Cells, Not DNA, Are The Master Architects Of Life,” in @NoemaMag.

[Image above: source]

* Psalm 139: 13–14

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As we delve into design, we might send insightful birthday greetings to Ernst Mayr; he was born on this date in 1904. A  taxonomist, tropical explorer, ornithologist, philosopher of biology, and historian of science, he is best remembered as one of the 20th century’s leading evolutionary biologists. His work contributed to the conceptual revolution that led to the modern evolutionary synthesis of Mendelian genetics, systematics, and Darwinian evolution, and to the development of the biological species concept.

His theory of peripatric speciation (a more precise form of allopatric speciation which he advanced), based on his work on birds, is still considered a leading mode of speciation, and was the theoretical underpinning for the theory of punctuated equilibrium, proposed by Niles Eldredge and Stephen Jay Gould. Mayr is sometimes credited with inventing modern philosophy of biology, particularly the part related to evolutionary biology, which he distinguished from physics due to evolutionary biology’s introduction of (natural) history into science.

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“The body is our general medium for having a world”*…

Leonardo’s Vitruvian Man

The biggest component in any human, filling 61 percent of available space, is oxygen. It may seem a touch counterintuitive that we are almost two-thirds composed of an odorless gas. The reason we are not light and bouncy like a balloon is that the oxygen is mostly bound up with hydrogen (which accounts for another 10 percent of you) to make water — and water, as you will know if you have ever tried to move a wading pool or just walked around in really wet clothes, is surprisingly heavy. It is a little ironic that two of the lightest things in nature, oxygen and hydrogen, when combined form one of the heaviest, but that’s nature for you. Oxygen and hydrogen are also two of the cheaper elements within you. All of your oxygen will set you back just $14 and your hydrogen a little over $26 (assuming you are about the size of Benedict Cumberbatch). Your nitrogen (2.6 percent of you) is a better value still at just forty cents for a body’s worth. But after that it gets pretty expensive.

You need about thirty pounds of carbon, and that will cost you $69,550, according to the Royal Society of Chemistry. (They were using only the most purified forms of everything. The RSC would not make a human with cheap stuff.) Calcium, phosphorus, and potassium, though needed in much smaller amounts, would between them set you back a further $73,800. Most of the rest is even more expensive per unit of volume, but fortunately only needed in microscopic amounts.

Thorium costs over $3,000 per gram but constitutes just 0.0000001 percent of you, so you can buy a body’s worth for thirty-three cents. All the tin you require can be yours for six cents, while zirconium and niobium will cost you just three cents apiece. The 0.000000007 percent of you that is samarium isn’t apparently worth charging for at all. It’s logged in the RSC accounts as costing $0.00.

Of the fifty-nine elements found within us, twenty-four are traditionally known as essential elements, because we really cannot do without them. The rest are something of a mixed bag. Some are clearly beneficial, some may be beneficial but we are not sure in what ways yet, others are neither harmful nor beneficial but are just along for the ride as it were, and a few are just bad news altogether. Cadmium, for instance, is the twenty-third most common element in the body, constituting 0.1 percent of your bulk, but it is seriously toxic. We have it in us not because our body craves it but because it gets into plants from the soil and then into us when we eat the plants. If you are from North America, you probably ingest about eighty micrograms of cadmium a day, and no part of it does you any good at all.

A surprising amount of what goes on at this elemental level is still being worked out. Pluck almost any cell from your body, and it will have a million or more selenium atoms in it, yet until recently nobody had any idea what they were there for. We now know that selenium makes two vital enzymes, deficiency in which has been linked to hypertension, arthritis, anemia, some cancers, and even, possibly, reduced sperm counts. So, clearly it is a good idea to get some selenium inside you (it is found particularly in nuts, whole wheat bread, and fish), but at the same time if you take in too much you can irremediably poison your liver. As with so much in life, getting the balances right is a delicate business.

Altogether, according to the RSC, the full cost of building a new human being, using the obliging Benedict Cumberbatch as a template, would be a very precise $151,578.46. … That said, in 2012 Nova, the long-running science program on PBS, did an exactly equivalent analysis for an episode called ‘Hunting the Elements’ and came up with a figure of $168 for the value of the fundamental components within the human body…

An excerpt from Bill Bryson’s The Body: A Guide for Occupants, via the ever-illuminating Delanceyplace.com: “How much, in materials, would it cost to build a human body?

* Maurice Merleau-Ponty, Phenomenology of Perception

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As we take our vitamins, we might we might send dynamically-evolved birthday greetings to Stephen Jay Gould; he was born on this date in 1941.  One of the most influential and widely read writers of popular science in his generation (e.g., Ever Since Darwin, The Panda’s Thumb), Gould was a highly-respected academic paleontologist, evolutionary biologist, and historian of science.  With Niles Eldridge, he developed the theory of “punctuated equilibrium,” an explanation of evolution that suggests (in contrast with the gradualism that was prevalent until then) that most evolution is marked by long periods of evolutionary stability, which are interrupted– “punctuated”– by rare instances of branching evolution (c.f., the Burgess Shale).

Scientists have power by virtue of the respect commanded by the discipline… We live with poets and politicians, preachers and philosophers. All have their ways of knowing, and all are valid in their proper domain. The world is too complex and interesting for one way to hold all the answers.

Stephen Jay Gould, Bully for Brontosaurus: Reflections in Natural History

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Names to all cattle, and to the fowl of the air, and to every beast of the field…

 

A murder of crows

From E.O. Wilson’s Encyclopedia of Life, via the TED Blog, a collection of very amusing (and altogether appropriate) animal group names: “Animals that travel in schools, towers, bloats and more.”

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As we noodle on nomenclature, we might send dynamically-evolved birthday greetings to Stephen Jay Gould; he was born on this date in 1941.  One of the most influential and widely read writers of popular science in his generation (e.g., Ever Since Darwin, The Panda’s Thumb), Gould was a highly-respected academic paleontologist, evolutionary biologist, and historian of science.  With Niles Eldridge, he developed the theory of “punctuated equilibrium,” an explanation of evolution that suggests (in contrast with the gradualism that was prevalent until then) that most evolution is marked by long periods of evolutionary stability, which are interrupted– “punctuated”– by rare instances of branching evolution (c.f., the Burgess Shale).

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Written by (Roughly) Daily

September 10, 2012 at 1:01 am