Human genomics
The Neanderthal genome will be fully sequenced. There will be no evidence of interbreeding with modern humans (although proponents of the multiregional model will remain unconvinced). By comparing this genome with ours, we may reconstruct the genome of archaic humans who lived almost a million years ago and who were ancestral to Neanderthals and modern humans.
Meanwhile, work will begin on sequencing the genome of early modern humans (10,000 – 40,000 years ago). This project should ultimately prove to be more interesting by showing us how much modern humans have evolved during their relatively short existence. We will probably find out that John Hawks erred on the low side in concluding that natural selection had changed 7% of the human genome over the past 40,000 years.
Darwin remembered
With the 150th anniversary of The Origin of Species, much will appear in 2009 about Charles Darwin and his life. We already know how he came up with his theory of evolution (Darwin salted away almost everything he wrote), although a few questions remain unanswered. What would he have done if he had lived longer? What did he have in mind for future projects?
Probably not much. He had said everything he wanted to say. The Origin of Species (1859) came out of a backlog that had built up in his mind during the previous twenty years. Then came The Descent of Man (1871), which used material left out of The Origin. Finally, The Expression of the Emotions in Man and Animals (1872) was largely a spin-off of The Descent. With this trilogy completed, he had little more to say. A younger Darwin might have addressed one of the dilemmas of evolution. How do selected characteristics perpetuate themselves? What keeps them from being blended away into non-existence with each generation of sexual reproduction? Darwin might have learned about another contemporary scientist, Gregor Mendel, and together the two of them might have proposed a particulate theory of genetics—more than thirty years before later evolutionists rediscovered Mendel’s work. The field of genetics would have developed much faster and, under Darwin’s guidance, may have avoided some of its later blind alleys (e.g., mutation pressure, saltationism, etc.).
Perhaps. But Darwin was unprepared for success. He had finally got to tell the world everything he had so long held back. And the world listened. From then on, a sense of emptiness took over, as if his remaining years were little more than an epilogue.
The Crisis?
The Second Great Depression will not begin in 2009. In any case, what scares me is not the prospect of a sudden drop in the standard of living. Rather, it’s that of a gradual decline to almost half its current value. That scenario is scarier and likelier. And it’s probably already started. For the past fifteen years, median wages have stagnated despite decent economic growth. What will happen when growth stays in the 0-2% range?
Some have suggested Darwin's theory wasn't really fully formed until shortly before he went public (after discovering Huxley was due to present a paper containing related ideas).
ReplyDeleteSexual Selection - Wikipedia
Charles Darwin...hypothesized a remote prehistoric time, when males had overwhelming selective.
power, and that it nonetheless affected males due to genetic correlation between the sexes. He also hypothesized that sexual selection could also be what had differentiated between different human races, as he did not believe that natural selection provided a satisfactory answer.
Not his least perceptive ideas, but with this pedigree why are they not accepted wisdom today?
For the past fifteen years, median wages have stagnated despite decent economic growth. What will happen when growth stays in the 0-2% range?
As they become impoverished with low standards of living Western industry/workers would become competitive with India and China.
OVERVIEW OF THE SYSTEM OF VITAMIN D
METABOLISM, AND ITS REGULATION.
If one looks at the system of vitamin D metabolism in Figure 2 from the perspective of a system
designed to control something, it becomes clear that this is a system better designed to cope with an abundance of supply, not a lack of it. The flow of vitamin D toward 25(OH)D is remarkably inefficient, with most bypassing
it. Furthermore, there is no way to correct for deficiency of vitamin D, other than to redirect utilization of 25(OH)D toward 1,25(OH)2D production, which is the pathway most acutely important for life. That is, when supplies of
vitamin D are severely restricted, its metabolism is directed only toward the maintenance of calcium
homeostasis. To expand on the point that the system of vitamin D metabolism is effectively a designed for adjusting for higher inputs, not lower inputs, I offer the example of an air-conditioner system. Air conditioners are designed to compensate for excessive heat, but they are a useless way to compensate for a cold environment.
here
Harvard Public Health Review spoke with HSPH Professor of Nutrition and Epidemiology Edward Giovannucci.
Q: What are the best sources of vitamin D?
A: The sun is the most potent source. When the sun’s ultraviolet rays hit the skin, the skin makes the vitamin, which is rapidly absorbed in the blood and can be stored for several months, mostly in the blood and fat tissue. This is why it’s hard to figure out how much supplemental vitamin D people might need.
If you spend a fair amount of time outdoors, you probably don’t need a vitamin D supplement. A light-skinned person living in Boston who takes walks in the summer with the face, neck, and arms exposed for 15 minutes gets enough. A 30-minute, full-body exposure to summer sun at noon without any sunscreen protection triggers the release of about 20,000 IU into the bloodstream. Most of that is stored.
Studies show that if you go out in the summer sun in your bathing suit until your skin just begins to turn pink, you make between 10,000 and 50,000 units of cholecalciferol in your skin. Professor Michael Holick of Boston University School of Medicine has studied this extensively and believes a reasonable average of all the studies is 20,000 units. That means a few minutes in the summer sun produces 100 times more vitamin D than the government says you need! As discussed in other pages, this is the single most important fact about vitamin D.
The vitamin D is produced by the solar UVB wavelength which is strongest when the sun is closest, around midday in the middle of summer. If we assume white skin evolved during a time of less UVB due to ice age weather, people would have evolved to maximize vitamin D during the summer and store it for the winter,(vitamin D can be stored in tissues).
If the synthesis of Vitamin D was so difficult due to low levels of UVB why would there be a mechanism to restrict it after only 20 minutes.
UVB is not strong enough in north Europe during the winter to make Vitamin D; therefore the storing of the Vitamin D synthesized in the body to tide one over the winter would seem to be logical.
My point is why would there be a limit on the manufacture of vitamin D in this brief period of high UVB?
The cloud and rain for much of the year you mention makes me wonder. Why have a mechanism to restrict UVB manufacture of Vitamin D, couldn't that excess be used in the winter?
The continuing existence of this stopping of Vitamin D manufacture in white skinned people a(after 20min body exposure) shows their skin was not related to a shortage of vitamin D, because thiss evolved mechanism (the stopping of of UVB manufactured vitamin D) the vitamin would have been the first thing to be modified. In other words the vit D would have continued to be synthesized and would then be stored for the winter.
It bears repeating, why are white people not an exception to the following?
If one looks at the system of vitamin D metabolism in Figure 2 from the perspective of a system
designed to control something, it becomes clear that this is a system better designed to cope with an abundance of supply, not a lack of it.
Why have north Europeans not evolved any changes to their limit of UVB synthesized Vitamin D (20,000IU) acording to Vitamin D3 Cholecalciferol Physiology
ReplyDelete"Studies show that if you go out in the summer sun in your bathing suit until your skin just begins to turn pink, you make between 10,000 and 50,000 units of cholecalciferol in your skin. Professor Michael Holick of Boston University School of Medicine has studied this extensively and believes a reasonable average of all the studies is 20,000 units. That means a few minutes in the summer sun produces 100 times more vitamin D than the government says you need! As discussed in other pages, this is the single most important fact about vitamin D.
The skin does another amazing thing with cholecalciferol. It prevents vitamin D toxicity. Once you make about 20,000 units, the same ultraviolet light that created cholecalciferol, begins to degrade it. The more you make, the more is destroyed. So a steady state is reached that prevents the skin from making too much cholecalciferol. This is why no one has ever been reported to develop vitamin D toxicity from the sun, though it is possible when taken orally.
Surely the first change under conditions of low UVB such that vitamin D would not be able to be synthesized for most of the year would be to the mechanism that broke down the excess. This excess would be stored for the winter.
Vitamin D can be stored of course :- The sun is the most potent source. When the sun’s ultraviolet rays hit the skin, the skin makes the vitamin, which is rapidly absorbed in the blood and can be stored for several months, mostly in the blood and fat tissue. This is why it’s hard to figure out how much supplemental vitamin D people might need.
Tod,
ReplyDeleteDarwin wrote a 230-page summary of his theory in 1844, which he showed to a few close associates. Sexual selection seems to have been a later theoretical development. It was not as well received back then and even today is still less broadly accepted than natural selection. I have a paper on this topic that will come out shortly ...
Your point on vitamin D synthesis is spot on. Why would northern Europeans have a mechanism for elimination of excess vitamin D if they had evolved white skin to cope with chronic vitamin D deficiency?
Normally, organisms quickly lose anything that is no longer necessary. Cave-dwelling fish and salamanders have lost all of their skin pigmentation -- because they no longer need it. Our ancestors lost the ability to synthesize vitamin C -- because they no longer needed it (there being plenty of fresh fruits and vegetables in their environment). Apparently the human genome still has the gene for vitamin D synthesis, but in a severely degraded and unusable state.
You've probably read this, still...
ReplyDeleteRace; John R. Baker,1974,Oxford University Press P.552, APPENDIX 8
Livingstone on evolution by sexual selection
"A NOTEWORTHY fact about Livingstone, which seems to have been overlooked by historians of biology is that he made a very short but very significant remark on sexual selection in relation to evolution. This was published in 1857, the year before Charles Darwin's preliminary paper was read before the Linnean Society, and two years before it was published. Livingstone remarks on the small size of most kinds of domestic animals in tropical Africa, and goes on: 'It is not from want of care in the breeding, for the natives always choose the larger and stronger males for stock, and the same arrangement prevails in nature, for it is only by overcoming their weaker rivals, that the wild males obtain possession of the herd. Invariably they show the scars received in battle.' [1] In his preliminary paper Darwin calls attention to 'the struggle of the males for the females. These struggles are generally decided by the law of battle...The results of the struggle among the males may be compared in some respects to those agriculturists who pay less attention to the careful selection of all their young animals and more to the occasional use of a choice male.' [2] Darwin introduced the term 'Sexual Selection' in 1859,in the first edition of his work On the origin of species. He defines it as the form of selection that 'depends not on a struggle for existence, but on a struggle between the males for the for possession of the females; the result is not death to the unsuccessful competitor, but few or no offspring. Generally, the most vigorous males those who are best fitted for their places, will leave most progeny.' In his book on The decent of man, and selection in relation to sex published in 1871, Darwin records Livingstone's remark about scars received in fights between males, but he makes no mention of the latter's idea of evolution through sexual selection, which is clearly implied in Livingstone's words recorded above"
[1] Livingstone,D., 1857. Missionary travels and researches in South Africa; including a sketch of sixteen years residence in the interior of Africa
[2] Darwin,C.,1859a, Extract from an unpublished work on species