Altricial mammals - large, helpless litters
Precocial mammals - small, able litters
What about us? Humans have small litters that are helpless! Why?
Answer -> Human babies are born as embryos, and they remain so for the next 9 months of their life.
If we measure time according to the rate of metabolism, almost all mammals live for the same amount of "time". For example, all mammals breathe the same number of times. Small, short-lived mammals just breathe (and metabolize) faster. By this relative measure of time, human gestation should take around 18 months.
Then why do births occur after just 9 months? Is it because we need the next 9 months to get familiar with the sights and sounds of the real world? No, the reason is more likely to be "mechanical". The culprit is our large brain. It would be hard for a delivery to happen if the brain became any larger!
Ever Since Darwin: Reflections in Natural History by Stephen Jay Gould
Monday, March 31, 2008
Sunday, March 30, 2008
Ever Since Darwin, 2: Human Evolution, 7: The Child as Man's Real Father
We evolved by retaining the youthful characters of our ancestors.
This process is called neoteny (literally, "holding youth")
Many of our adult features are similar to the juvenile features of other primates.
This delayed development is a basic event in human (and primate) evolution.
We live longer and mature more slowly than mammals of comparable body size.
Humans have the most protracted period of infancy, childhood and juvenility.
Nearly 30% of our life is spent growing.
What is the adaptive significant of retarded development?
Humans are not particularly strong, swift or well-designed. We don't reproduce rapidly.
We are a learning animal and our primary advantage is our brain.
To enhance our learning, we have lengthened our childhood by delaying sexual maturation with its adolescent yearning for independence. Our children are tied for longer periods to their parents, increasing their learning time and strengthening family ties.
Ever Since Darwin: Reflections in Natural History by Stephen Jay Gould
This process is called neoteny (literally, "holding youth")
Many of our adult features are similar to the juvenile features of other primates.
This delayed development is a basic event in human (and primate) evolution.
We live longer and mature more slowly than mammals of comparable body size.
Humans have the most protracted period of infancy, childhood and juvenility.
Nearly 30% of our life is spent growing.
What is the adaptive significant of retarded development?
Humans are not particularly strong, swift or well-designed. We don't reproduce rapidly.
We are a learning animal and our primary advantage is our brain.
To enhance our learning, we have lengthened our childhood by delaying sexual maturation with its adolescent yearning for independence. Our children are tied for longer periods to their parents, increasing their learning time and strengthening family ties.
Ever Since Darwin: Reflections in Natural History by Stephen Jay Gould
Ever Since Darwin, 2: Human Evolution, 6: Bushes and Ladders
A ladder is not the right metaphor for evolution. A bush is.
New species arise in very small populations that become isolated from their parental group at the periphery of the ancestral range, the "bush". Speciation in these branched groups is very fast by evolutionary standards - hundreds or thousands of years (a geological microsecond).
The steps of this speciation might not be captured in fossils since it happens very fast. We encounter the new species when it reinvades the ancestral range and becomes a major population by itself. The process repeats and we find "sudden" changes in fossil records.
There were several co-existing brances of the human bush. We are merely the surviving branch.
Ever Since Darwin: Reflections in Natural History by Stephen Jay Gould
New species arise in very small populations that become isolated from their parental group at the periphery of the ancestral range, the "bush". Speciation in these branched groups is very fast by evolutionary standards - hundreds or thousands of years (a geological microsecond).
The steps of this speciation might not be captured in fossils since it happens very fast. We encounter the new species when it reinvades the ancestral range and becomes a major population by itself. The process repeats and we find "sudden" changes in fossil records.
There were several co-existing brances of the human bush. We are merely the surviving branch.
Ever Since Darwin: Reflections in Natural History by Stephen Jay Gould
Ever Since Darwin, 2: Human Evolution, 5: A Matter of Degree
We only have differences in degree (of features) with chimpanzees, there are no unambiguous differences of kind. We differ just quantitatively, not qualitatively.
The genetic distance between us and chimps is very small (small enough that interbreeding might be possible). Then why the vast differences in form and behavior? Genes do not just determine traits. During development, different genes must turn on and off with exquisite timing to achieve differences from the same genetic system. For example, when a hand forms from a homogeneous limb bud, cells must proliferate in some areas (destined to be fingers) and die in others (the spaces between them).
We have genetic differences most likely in regulatory genes, that control this timing, resulting in large differences with only a few (relatively) differing genes.
Ever Since Darwin: Reflections in Natural History by Stephen Jay Gould
The genetic distance between us and chimps is very small (small enough that interbreeding might be possible). Then why the vast differences in form and behavior? Genes do not just determine traits. During development, different genes must turn on and off with exquisite timing to achieve differences from the same genetic system. For example, when a hand forms from a homogeneous limb bud, cells must proliferate in some areas (destined to be fingers) and die in others (the spaces between them).
We have genetic differences most likely in regulatory genes, that control this timing, resulting in large differences with only a few (relatively) differing genes.
Ever Since Darwin: Reflections in Natural History by Stephen Jay Gould
Ever Since Darwin, 1: Darwiniana, 4: Darwin's Untimely Burial
Darwin's theory of natural selection has been a perennial candidate for burial.
Does the theory have a logical error in its formulation?
Natural selection was defined by Herbert Spencer as "survival of the fittest".
Is fitness just "differential reproductive success"?
If fitness is defined in terms of survival, Spencer's phrase becomes a tautology - "survival of those who survive".
Darwin did propose an independent criterion but relied upon an analogy - artificial selection of the fittest by animal breeders. But nature is no animal breeder. How is the analogy valid?
The breeder's priorities represent a "change in environment" for the animals. Superior design in changed environments is an independent criterion of fitness. Thus, survival is a result of fitness, not a definition of it.
Ever Since Darwin: Reflections in Natural History by Stephen Jay Gould
Does the theory have a logical error in its formulation?
Natural selection was defined by Herbert Spencer as "survival of the fittest".
Is fitness just "differential reproductive success"?
If fitness is defined in terms of survival, Spencer's phrase becomes a tautology - "survival of those who survive".
Darwin did propose an independent criterion but relied upon an analogy - artificial selection of the fittest by animal breeders. But nature is no animal breeder. How is the analogy valid?
The breeder's priorities represent a "change in environment" for the animals. Superior design in changed environments is an independent criterion of fitness. Thus, survival is a result of fitness, not a definition of it.
Ever Since Darwin: Reflections in Natural History by Stephen Jay Gould
Friday, March 28, 2008
Ever Since Darwin, 1: Darwiniana, 3: Darwin's Dilemma: The Odyssey of Evolution
Darwin, Lamarck and Haeckel - the greatest 19th century evolutionists of England, France and Germany respectively - did not use the word evolution in the original editions of their great works.
Evolution had another technical meaning in Darwin's time - a theory that all future generations existed, like Russian dolls, in the ova of Eve or sperm of Adam. Latin evolvere means "to unroll".
However, by 1859, evolution was losing this meaning. It had become a common English word and embodied a concept of progressive development. It was available as a description for Darwin's "descent with modification".
Darwin, though, did not like the term evolution because he was uncomfortable with the notion of inevitable progress inherent in its vernacular meaning. Darwin stood almost alone in insisting that organic change led only to increasing adaptation between organisms and their own environment and not to an abstract ideal of progress - never say higher or lower.
Evolution has no necessary links to progress. Scientists know this but most laymen still associate evolution with progress, not simply as change.
Ever Since Darwin: Reflections in Natural History by Stephen Jay Gould
Evolution had another technical meaning in Darwin's time - a theory that all future generations existed, like Russian dolls, in the ova of Eve or sperm of Adam. Latin evolvere means "to unroll".
However, by 1859, evolution was losing this meaning. It had become a common English word and embodied a concept of progressive development. It was available as a description for Darwin's "descent with modification".
Darwin, though, did not like the term evolution because he was uncomfortable with the notion of inevitable progress inherent in its vernacular meaning. Darwin stood almost alone in insisting that organic change led only to increasing adaptation between organisms and their own environment and not to an abstract ideal of progress - never say higher or lower.
Evolution has no necessary links to progress. Scientists know this but most laymen still associate evolution with progress, not simply as change.
Ever Since Darwin: Reflections in Natural History by Stephen Jay Gould
Ever Since Darwin, 1: Darwiniana, 2: Darwin's Sea Change or Five Years at the Captain's Table
Trick question: Who was the naturalist aboard the H.M.S. Beagle?
Answer: Not Darwin, the official naturalist was the ship's surgeon, Robert McKormick, even though Darwin's efforts began to outstrip his collections, forcing McKormick to go home.
In those days, British naval tradition dictated that a captain have virtually no contact with anyone down the chain of command. These voyages lasting many years, with only a very limited contact by mail with friends and families, can exert a heavy psychological toll. The previous captain of Beagle had shot himself to death during his third year away from home. Darwin sailed on the Beagle as a companion to Captain Fitzroy since he had the right social standing.
Fitzroy believed in "god's design" while Darwin proposed a natural explanation for the perfection of organic structure. Discussions with Fitzroy while dining with him every day for five years, without being able to rebuke him, might have been more important than the finches of Galapagos in inspiring the materialistic and antitheistic tone of Darwin's philosophy and evolutionary theory. For five long years, one of the most brilliant men in recorded history kept his peace.
After the voyage, Fitzroy began to see himself as the unwitting agent of Darwin's heresy. He shot himself eventually.
Ever Since Darwin: Reflections in Natural History by Stephen Jay Gould
Answer: Not Darwin, the official naturalist was the ship's surgeon, Robert McKormick, even though Darwin's efforts began to outstrip his collections, forcing McKormick to go home.
In those days, British naval tradition dictated that a captain have virtually no contact with anyone down the chain of command. These voyages lasting many years, with only a very limited contact by mail with friends and families, can exert a heavy psychological toll. The previous captain of Beagle had shot himself to death during his third year away from home. Darwin sailed on the Beagle as a companion to Captain Fitzroy since he had the right social standing.
Fitzroy believed in "god's design" while Darwin proposed a natural explanation for the perfection of organic structure. Discussions with Fitzroy while dining with him every day for five years, without being able to rebuke him, might have been more important than the finches of Galapagos in inspiring the materialistic and antitheistic tone of Darwin's philosophy and evolutionary theory. For five long years, one of the most brilliant men in recorded history kept his peace.
After the voyage, Fitzroy began to see himself as the unwitting agent of Darwin's heresy. He shot himself eventually.
Ever Since Darwin: Reflections in Natural History by Stephen Jay Gould
Thursday, March 27, 2008
Ever Since Darwin, 1: Darwiniana, 1: Darwin's Delay
Darwin developed his theory of evolution in 1838 but published it 21 years later. Why? Was he afraid of sounding heretical? No, evolution was a heresy but a common and well-discussed one.
He was afraid of exposing something far more heretical: Philosophical Materialism - the idea that matter is the stuff of all existence and all mental and spiritual phenomena are its by-products.
The most ardent materialists of the 19th century, Marx and Engels, recognized Darwin's accomplishment. In fact, Marx offered to dedicate volume 2 of Das Kapital to Darwin (who declined since he hadn't read the German work)
Darwin eventually published The Origin of Species in 1869 but only because A. R. Wallace was about to scoop him.
Ever Since Darwin: Reflections in Natural History by Stephen Jay Gould
He was afraid of exposing something far more heretical: Philosophical Materialism - the idea that matter is the stuff of all existence and all mental and spiritual phenomena are its by-products.
The most ardent materialists of the 19th century, Marx and Engels, recognized Darwin's accomplishment. In fact, Marx offered to dedicate volume 2 of Das Kapital to Darwin (who declined since he hadn't read the German work)
Darwin eventually published The Origin of Species in 1869 but only because A. R. Wallace was about to scoop him.
Ever Since Darwin: Reflections in Natural History by Stephen Jay Gould
The Colossal Book of Mathematics by Martin Gardner
This is a book of recreational mathematics. I could not finish this book as I had to return it to library. Some of the sections in the book that are of interest are (directly from my notebook):
1. Rep-n Polygons
2. Piet Heins Superellipse
Super Egg - Exponent 2-1/2 . Columbus experiment of making an egg stand
Interesting Fact: If Center of Curvature is above Center of Gravity the superegg will be stable -P69 -> Wiki
3. Planiverse - 2D universe - very interesting depiction of men and women
4. Helix and its importance - The shape is everywhere - shapes of nut & bolts , horns ,sea shells, snails shells, DNA molecules -> can be both right handed and left handed
5. Spheres & Hyperspheres
137 -> a2+b2+c2+d2=r2 is called hypersphere in 4 dimensions
surface of a n-sphere has a dimensionality of n-1. Does this mean that 3-space is actually the hypersurface of the vast 4-sphere.
If space is a hypersphere, then that hypersphere must sit in a four-dimensional Euclidean space, allowing us to view it from the outside. Nature, however, need not cling to this notion. It would be perfectly acceptable for the universe to be a hypersphere and not be embedded in any higher-dimensional space. Such an object may be difficult to visualize, because we are used to viewing shapes from the outside. But there need not be an "outside."
Good Explanation: Paradigm Shifts in Astronomy and Cosmology - More
6. The Church of Fourth Dimension
I had to stop here. I will provide some updates on more sections once I get the book back.
The Colossal Book of Mathematics>
1. Rep-n Polygons
2. Piet Heins Superellipse
Super Egg - Exponent 2-1/2 . Columbus experiment of making an egg stand
Interesting Fact: If Center of Curvature is above Center of Gravity the superegg will be stable -P69 -> Wiki
3. Planiverse - 2D universe - very interesting depiction of men and women
4. Helix and its importance - The shape is everywhere - shapes of nut & bolts , horns ,sea shells, snails shells, DNA molecules -> can be both right handed and left handed
5. Spheres & Hyperspheres
137 -> a2+b2+c2+d2=r2 is called hypersphere in 4 dimensions
surface of a n-sphere has a dimensionality of n-1. Does this mean that 3-space is actually the hypersurface of the vast 4-sphere.
If space is a hypersphere, then that hypersphere must sit in a four-dimensional Euclidean space, allowing us to view it from the outside. Nature, however, need not cling to this notion. It would be perfectly acceptable for the universe to be a hypersphere and not be embedded in any higher-dimensional space. Such an object may be difficult to visualize, because we are used to viewing shapes from the outside. But there need not be an "outside."
Good Explanation: Paradigm Shifts in Astronomy and Cosmology - More
6. The Church of Fourth Dimension
I had to stop here. I will provide some updates on more sections once I get the book back.
The Colossal Book of Mathematics>
Ever Since Darwin, Prologue
Darwin convinced the thinking world, within a decade, that evolution had occurred but his own theory of natural selection didn't prevail until the 1940s. Even today it is misunderstood.
However, natural selection is just two facts and one conclusion:
* organisms vary and the variations are inherited (at least in part) by their offspring
* organisms produce more offspring than can possibly survive
=> Organisms varying in directions favored by the environment will survive and propagate.
Darwin contended that natural selection is a creative force, not just an executioner of the unfit. It must construct the fit as well. This is accomplished by small, random variations that are not predirected in favorable ways.
Evolution is a mixture of chance and necessity - chance at the level of variation, necessity in the level of selection.
Ever Since Darwin: Reflections in Natural History by Stephen Jay Gould
However, natural selection is just two facts and one conclusion:
* organisms vary and the variations are inherited (at least in part) by their offspring
* organisms produce more offspring than can possibly survive
=> Organisms varying in directions favored by the environment will survive and propagate.
Darwin contended that natural selection is a creative force, not just an executioner of the unfit. It must construct the fit as well. This is accomplished by small, random variations that are not predirected in favorable ways.
Evolution is a mixture of chance and necessity - chance at the level of variation, necessity in the level of selection.
Ever Since Darwin: Reflections in Natural History by Stephen Jay Gould
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