Dan masih ada manusia berotak anjing, baik yang beragama islam maupun yang
beragama Nasrnai yang bilang teori Darwin hanya ngibuo dan telah dipatahkan...
Menyedihkan, sungugh menyedihkan betapa ortak mereka itu telah di rusak dan
dibusukkan oleh ajaran agama semitik yang hanya berdasarkan omong kosong dan
kibulan itu.
Adalah bahagian dari usaha pecerdasan manusia Indoneisa untuk menunjukkan
betapa dungunya ajaran agama semitik yang seperti juga ajaran agama lain
hanyalah tahayul dan berdasarkane kapada omong kosong dan kibulan doang.
---
Thursday, Feb. 12, 2009
The Ever Evolving Theories of Darwin
By Carl Zimmer
What do Harry Potter, Sherlock Holmes, G.I. Joe and Charles Darwin have in
common? They will all be coming to movie theaters this year. The only real
person on that list will be played by Paul Bettany in the biopic Creation. And
in true celebrity fashion, Darwin will be everywhere this year. In a
convergence of anniversaries, Darwin would have turned 200 years old on Feb.
12, and his landmark book, On the Origin of Species, turns 150 on Nov. 24.
There will be documentaries, lectures, conferences and museum exhibits.
Darwin-themed blogs are being launched, and a cartload of Darwin-related books
are being published. A replica of H.M.S. Beagle, the ship that carried Darwin
around the world, will retrace his path. This January, Stanford University let
a group of 90 people do likewise--albeit more comfortably, on a private Boeing
757.
It's only fitting to recognize the accomplishments of a great biologist. But
there's a risk to all this Darwinmania: some people may come away with a
fundamental misunderstanding about the science of evolution. Once Darwin mailed
his manuscript of On the Origin of Species by Means of Natural Selection, or
the Preservation of Favoured Races in the Struggle for Life to his publisher,
the science of evolution did not grind to a halt. That would be a bit like
saying medicine peaked when Louis Pasteur demonstrated that germs cause
diseases.
Today biologists are exploring evolution at a level of detail far beyond what
Darwin could, and they're discovering that evolution sometimes works in ways
the celebrated naturalist never imagined. "The biological problems we're
dealing with are much more complex," says Massimo Pigliucci, an evolutionary
biologist at Stony Brook University in New York. "That said, it's a lot of fun.
I'm not complaining."
Darwin developed his theory by gathering as much information as he could about
life. He collected it while voyaging on the Beagle, by sitting in front of a
microscope back in England and by writing to a global network of
correspondents. Today, however, biologists can feast on a far bigger banquet of
data. The fossil record was scanty in Darwin's day, but now it has pushed the
evidence of life on Earth back to at least 3.4 billion years ago. And while
Darwin recognized that variation and heredity were the twin engines that made
evolution possible, he didn't know what made them possible. It would take
almost a century after the publication of On the Origin of Species for
biologists to determine that the answer was DNA.
DNA is like a genetic cookbook, using four molecular "letters" to spell out
recipes for everything from hormones to heart valves. Biologists today are
reading the 3.5 billion letters in the human genome as well as the DNA from
thousands of other species, and they've amassed vast databases of genetic
information that they can rummage through to learn about how life evolved.
Time and again, biologists are finding that Darwin had it right: evolution is
the best way to explain the patterns of nature. "You just can't even start to
make sense of all this data without a framework of evolution," says Günter
Wagner, an evolutionary biologist at Yale University.
Darwin proposed that natural selection could gradually transform a species.
Scientists have observed thousands of cases of natural selection in action.
They've documented that beaks of finches on the Galápagos Islands have gotten
thicker when droughts forced the birds to crack tough seeds to survive. They've
observed bacteria develop resistance to drugs that were believed to be
invincible. Now biologists are applying DNA-sequencing technology to natural
selection, which lets them identify the individual genetic changes that boost
reproductive success.
As populations adapt to their surroundings, they can gradually evolve into new
species. "We now have, I think, a good understanding of how new species
arise--that is, how biological diversity is created," says Jerry Coyne, an
evolutionary biologist at the University of Chicago and the author of the new
book Why Evolution Is True. "Darwin made little inroad into the problem,
despite the title of his magnum opus."
Biologists have also found plenty of evidence to support Darwin's other major
claim: that different species share a common ancestry. Over the past 15 years,
for example, paleontologists have found several fossils of whales with legs,
linking modern whales to their terrestrial ancestors. Besides studying fossils,
biologists can discover the genealogy of species by looking at their DNA. The
fossil record points to hippos and other hoofed mammals as being the closest
living relatives of whales. So does their DNA. Our own DNA contains clues to
the bonds we share with the rest of life--it turns out, for instance, that we
are closer kin to mushrooms than to sunflowers.
It's been 1.5 billion years or more since our ancestors split off from our
fungal cousins. How did the genome of our ancestor change so that it could
produce two-legged primates? One part of the answer is that mutations over time
altered genes that encode proteins, and some of those changes have been favored
by natural selection. But that does not mean that our genome--the sum total of
our human DNA--is a finely tuned collection of protein-coding genes. In fact, a
lot of mutations that all humans carry neither helped nor harmed our ancestors.
They spread just by chance. And a lot of our genome is not made up of
protein-coding genes. In fact, 98.8% of it is not. Some of that 98.8% consists
of "pseudogenes"--genes that once encoded proteins but no longer can because of
a crippling mutation. They are the molecular equivalent of a vestigial tail,
allowing us to see evolution's track.
Biologists are a long way from understanding the entire genome, but as they get
to know its parts better, they're getting a more precise comprehension of one
of the most important features of evolution: how complex organs evolve. The
notion that something as intricate as an eye could have evolved, Darwin wrote,
"seems, I freely confess, absurd in the highest degree." But he argued that new
complex organs could evolve through a series of intermediate forms.
Paleontologists can track some of life's transformations in fossils--observing
how fins gradually evolved into feet, for example. But fins and feet and other
complex structures are also encoded in DNA, and until the 1980s, biologists had
almost no knowledge of the genes that built them. Over the past 25 years,
biologists have identified many of the genes that help build embryos. A number
of them help lay out the embryo's blueprint by letting cells know where they
are. The cells absorb proteins floating around them, and the signals trigger
the cells to make other proteins, which in turn clamp onto certain bits of DNA
to switch neighboring genes on and off. This network of genes eventually leads
a cell to give rise to an arm or a brain or a tongue.
These networks are so intricate that they probably put some limits on
evolution's creative potential. Once a lineage of animals evolves networks for
arms and legs, it's not easy for evolution to rewire the networks to produce,
say, wheels. For one thing, many networks share some of the same genes. A
change to a gene that improves one network may wreck another one. So for the
most part, we're stuck with what evolution gave us.
Nevertheless, new traits have evolved. Once there were no brains, and now there
are billions. Once you could search the entire world and never find a leaf. Now
the world is green. Biologists are discovering some of the genetic secrets for
evolving new traits. One is to recycle old genes.
Growing hair, for example, is a trait that evolved only in mammals. One of the
key proteins in our hair is known as alpha-keratin. Not long ago, some Austrian
and Italian researchers decided to search for alpha-keratin genes in animals
that lack hair. They found those genes in chickens and lizards--which belong to
the closest living lineages to mammals. Lizards build alpha-keratin in their
claws. And it turns out that mammals do as well. The research suggests that the
hairless ancestors of today's mammals already had alpha-keratin that was used
to build their claws; only later was alpha-keratin borrowed to help build hair.
Darwin had no way of knowing this, since he had no way of examining DNA. If he
did, he might well have rethought one of his most potent metaphors for
evolution: the tree of life. It's not that the metaphor is wrong. Scientists
regularly reconstruct evolutionary branches today. When a new disease breaks
out, for example, the fastest way to figure out what to do is to determine what
the pathogen is related to.
But there's more to the history of life than the branching of a tree. Every now
and then, DNA moves between species. Viruses ferry genes from one host to
another. Bacteria swap genes inside our bodies, evolving resistance to
antibiotics in our own gut. Some 2 billion years ago, one of our single-celled
ancestors took in an oxygen-consuming bacterium. That microbe became the
thousands of tiny sacs found in each of our cells today, known as mitochondria,
that let us breathe oxygen. When genes move this way, it's as if two branches
of the tree of life are being grafted together.
Biologists have documented a vast amount of gene-swapping among single-celled
organisms--which happen to make up most of the diversity of life on Earth.
There are 10,000 species of bacteria in a spoonful of dirt, twice as many
species as all the mammals in the world. In the genome of a typical microbe,
most of the genes hopped from one species to another at some point in the
history of life. In some ways, the history of life is indeed like a tree,
sprouting new branches. But in some ways, it's also like a tapestry, emerging
from a loom, its genetic threads woven together in new combinations.
In the mid-1900s, biologists succeeded in merging the newest biological
developments at the time into a new vision of evolution known as the Modern
Synthesis. Today a number of biologists argue that it's time for a new
understanding of evolution, one that Pigliucci has called the Extended
Evolutionary Synthesis. For now, they are fiercely debating every aspect of
that synthesis--how important gene-swapping is to the course of evolution, for
instance, and how gene networks get rewired to produce new traits.
Some researchers argue that many patterns of nature--such as the large number
of species in the tropics--cannot be reduced to the effect of natural selection
on individuals. They may be following rules of their own. "Which of these ideas
is going to actually survive and prove fruitful is anybody's guess," says
Pigliucci. "I don't see things coalescing for at least a decade or more."
Darwin predicted this. "We can dimly foresee that there will be a considerable
revolution in natural history," he wrote at the end of On the Origin of
Species. He saw his work not as the end of biology but as a beginning.
Putting Evolution to The Test. How does Darwin hold up?
Darwin's microscope. His research, given the technology, was robust
[This article contains a table. Please see hardcopy of magazine or PDF.]
DARWIN TODAY Species share a common ancestry, like branches on a tree Genetic
studies confirm that different species have evolved from common ancestors. But
DNA has also jumped from one species to another--turning parts of the tree of
life into a web Humans evolved from apes in Africa Evidence from DNA indicates
that chimpanzees and bonobos are the closest living relatives to humans.
Fossils document the course of human evolution in Africa from apelike ancestors
over the past 7 million years Natural selection is a powerful force driving
evolution Natural selection's fingerprints can be detected in the human genome.
But many mutations have spread thanks to pure chance (a process known as
genetic drift) Complex traits like eyes can evolve through a series of
intermediate steps Fossils have documented some of those steps in structures
such as limbs and ears. Studies on DNA have shown how genes for building old
organs have been "borrowed" to help build new
ones
Zimmer is the author of the forthcoming book The Tangled Bank: An Introduction
to Evolution
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* http://www.time.com/time/magazine/article/0,9171,1879213,00.html
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Jusfiq Hadjar gelar Sutan Maradjo Lelo
Allah yang disembah orang Islam tipikal dan yang digambarkan oleh al-Mushaf itu
dungu, buas, kejam, keji, ganas, zalim lagi biadab hanyalah Allah fiktif.
