individuals hear sounds ... when they see things move or flash. ..."

Charles Darwin, a Hero of Humankind,
born 200 years ago
(Top Posts - Science - 012009)

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February 12, 1809, a monumental day in
the evolution of humankind from ignorance
and myth -to- a much deeper understanding
of the place of homo sapiens and all life in
a naturalistic world.

The following excerpts briefly touch on the
subjects in each article. For complete informa-
tion, access each of the links listed below.

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January 2009
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This special web edition of Science News
includes expanded versions of articles from
the magazine's print edition plus two addi-
tional features, all commemorating the
200th anniversary of the birth of Charles

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Darwin's Evolution
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Two centuries ago, modern biology's found-
ing father was born in England. He became
the most celebrated scientist of his time, deci-
phering the records of life's history from
creatures extinct and living and thereby ex-
plaining the genesis of life's diversity.

Charles Darwin was born into a world that
today's scientists wouldn't recognize.

When baby Darwin arrived on February 12,
1809, modern science was also in its infancy.

 o Dalton had just recently articulated the modern
    theory of the chemical atom, but nobody had
    any idea what atoms were really like.

 o Physicists had not yet heard of the conservation
    of energy or any other laws of thermodynamics.

 o Faraday hadn't yet shown how to make electri-
    city from magnetism, and no one had a clue
    about light's electromagnetic identity.

 o Geology was trapped in an ante-diluvian para-
    digm, psychology hadn't been invented yet and
    biology still seemed, in several key ways, to be
    infused with religion, resistant to the probes of
    experiment and reason.

Then came Darwin. By the time he died in 1882,
thermodynamics possessed two unbreakable laws,
chemistry had been codified in Mendeleyev's peri-
odic table, Maxwell had discovered the math merg-
ing electricity and magnetism to explain light.

Lyell had established uniformitarianism as the
basis for geology, Wundt had created the first
experimental psychology laboratory, and science
had something substantial to say about how life
itself got to be the way it was - thanks to Dar-
win's perspicacious curiosity, intellectual rigor,
personal perseverance and power of persuasion.


Today Darwin's original idea survives, although
it has spawned many mutated forms, with nuances
and complexities that make evolutionary science
a constantly advancing field of research.

And Darwin's logic has been borrowed by other
investigators in diverse disciplines:

 o Psychologists try to explain behavior based on
    what mental habits would have enhanced sur-
    vival as human ancestors were evolving.

 o Biomedical researchers grapple with evolution-
    ary principles in fighting microbial resistance
    to antibiotics.

 o Computer scientists mix and select segments
    of binary code to generate optimal computer

 o Even in physics, the word "Darwinian" appears
    in papers on thermodynamics, quantum physics
    and black holes.

Darwin would have been fascinated by such research
and would no doubt have understood a lot of it, as
so much of the underlying reasoning was his.

Darwin would also have been happy with the many
modifications and adaptations to his ideas found in
modern reformulations of evolutionary theory:

 o Speciation isn't always gradual, change isn't
    always the result of selection, organisms are not
    the only units of selection, evolutionists now

 o Darwin foresaw some of these views, and he
    would have embraced them all - as a man of
    science willing "to give up any hypothesis, how-
    ever much beloved ... as soon as facts are shown
    to be opposed to it," in his words. "If I know
    myself, I work from a sort of instinct to try to
    make out truth."

And in the battle to wrest truth from nature, none
fought better than Darwin.

"He found a great truth," Huxley wrote in Darwin's
obituary, "trodden under foot, reviled by bigots, and
ridiculed by all the world; he lived long enough to
see it, chiefly by his own efforts, irrefragably estab-
lished in science, inseparably incorporated with the
common thoughts of men."

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Evolution's Evolution
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Darwin's dangerous idea has adapted to modern

Just a decade after he published On the Origin of
Species, Charles Darwin was already worrying
about the evolution of his idea.

In an 1869 letter to botanist Joseph Dalton Hooker,
Darwin lamented:

"If I lived twenty more years and was able to work,
how I should have to modify the Origin, and how
much the views on all points will have to be mod-
ified! Well, it is a beginning, and that is something."

Calling the Origin a mere "beginning" is like saying
the Beatles were just a rock band or that Shakespeare
wrote some decent plays.

Darwin's gifts to science were radical. He not only
proposed that all of Earth's diverse beings shared
a common ancestry, but also described an elegant
mechanism to explain how all that diverse life came
to be.

Darwin was a master of merging data from different
disciplines, pain-stakingly drawing from zoology,
botany, geology and paleontology to build a solid
foundation for evolutionary biology. Today, 150
years later, scientists continue to grapple with ideas
descended from that foundation. Still, Darwin's
central tenets survive, fit enough to frame the
questions posed by modern biology.


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Molecular Evolution
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Investigating the genetic books of life reveals new
details of 'descent with modification' and the forces
driving it.

Charles Darwin didn't know about genes and DNA.
In fact, hardly anyone noticed when Gregor Mendel,
a monk whose pea experiments eventually led to
modern genetics, published his findings in an ob-
scure journal a few years after Darwin's On the
Origin of Species appeared in 1859.

It would take nearly a century more before James
Watson and Francis Crick deciphered the structure
of DNA, the molecule that contains the manual for
building an organism.

Yet Darwin was still able to describe a mechanism
 - natural selection - for how evolution shapes
life on Earth. That's like describing how a car
works without knowing about the existence of
internal combustion engines.

But while Darwin achieved his insights without
molecular help, biologists today are intimately
familiar with the molecules responsible for the
diverse array of plants, animals and other organ-
isms that populate the planet.

The study of genes has revealed evolution as
essentially a high-stakes poker game in which
organisms draw randomly from a deck of genetic

At stake is the chance to pass along genes to the
next generation. Sometimes the hand is good
enough to get ahead in the game, but some hands
are losers, perhaps to the extent of extinction.

By studying the winners, scientists are learning
how the forces of evolution work on DNA, the
biochemical repository of an organism's entire
natural history.

DNA records the mutations that helped some
animals to survive ice ages while others perished,
the nips and tucks that make animals more attrac-
tive to mates, the big leaps that allowed plants to
become domestic crops - they're all there, writ-
ten out in a simple alphabet of four letters.

Each organism has its own book of life, but it's
not a just-so story. The genomes of living things
are constantly undergoing editing and revision.
And each individual has its own edition of its
species's book, shaped by natural selection and
the other, perhaps less-appreciated forces of
genetic mutation, recombination and drift.


Scientists are now beginning to learn how tweaks
and major changes on the molecular level enable
adaptation to environments. The picture is painted
in DNA, but it's far from a completed masterpiece.

Changing environments coupled with the forces
of natural selection, mutation, recombination and
drift are continually reworking the painting. Only
time will tell how the landscape will morph - and
its inhabitants with it.

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Step-by-step Evolution
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Mining the gaps: The in-between fossils are the hard-
est to find, but they tell the best stories.

When Charles Darwin proposed the idea of evolution
in On the Origin of Species, he wrote "if my theory be
true, numberless intermediate varieties, linking most
closely all the species of the same group together,
must assuredly have existed." At the same time, he
bemoaned the dearth of such transitional fossils as
perhaps "the most obvious and gravest objection
which can be urged against my theory."

Surely it was serendipity when, just two years later,
quarriers unearthed fossils of Archaeopteryx. This
creature, now recognized by many scientists as the
first known bird, has a mosaic of features that links
it with the disparate groups of species on either side
of it in the fossil record: While its teeth, tail and
overall body shape are distinctly reptilian, its fea-
thers have the same complex structure as the lift-
generating feathers of modern birds. In other words,
it is just one of the "numberless intermediate vari-
eties" that Darwin predicted must have existed.

"It was the right discovery at the right time," says
Richard Fortey, a paleontologist at the Natural
History Museum in London.

Darwin blamed the lack of transitional fossils in
part on the poorness of the paleontological record.
It's a rare accumulation of fortuitous events when
a creature is fossilized, its remains are preserved
over millions of years and then those remains are


Many of the gaps in the fossil record that remained
unfilled in Darwin's time now throng with creatures,
such as the ones used to chronicle the 48-million-
year series of evolutionary changes between whales
and their predecessors. And particular biomarkers
 - chemical fossils, if you will - in rocks more
than 240 million years old have provided clues
about the evolution of flowering plants.

Paleontologists still randomly stumble across tran-
sitional fossils these days, such as a creature found
in Texas that falls in a 50-million-year gap in am-
phibian evolution and helps pin down when the
groups that include salamanders and frogs arose.

As often as not, however, transitional fossils are
found when researchers head into the field with
a specific target in mind: By focusing on rocks
deposited during an interval where gaps in the
fossil record exist, scientists can boost the chances
of making a critical discovery. That's how research-
ers unearthed Tiktaalik, a 2.7-meter-long beast that
plopped into a 9-million-year gap in the chronicle
of vertebrates' transition from water to land.


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Computing Evolution
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Scientists sift through genetic data sets to better
map twisting branches in the tree of life.

Among its many prose-filled pages, Charles Dar-
win's On the Origin of Species includes only one
illustration. It's a diagram of short lines leading
upward from the base - a few lines at the bottom
branch out repeatedly as they extend up.

Darwin meant for the image to depict what he
dubbed the "tree of life." This figure embodied
Darwin's vision for how the tremendous diversity
of life on Earth arose.

A few species - the base of the tree - mutate and
evolve over time, sometimes branching to form new
species. An ancient species of bird might colonize a
chain of islands and slowly evolve narrower beaks or
other features specialized for the birds' new habitats.

Eventually, groups in different habitats become separ-
ate species, and each species continues to evolve and
adapt, perhaps branching again. In this way, the first
fishlike land animals gave rise to the great diversity
of amphibians, lizards, insects, rodents, marsupials,
primates and birds.

It was a sweeping vision of life, revealing it to be a
giant family with a vast genealogy.

Branches of the tree show the kinship among creatures
and the history of change and adaptation.

Darwin toiled for much of his life to understand the
relationships among species, the branches of this
immense tree, by gathering countless specimens and
scrutinizing their similarities and differences - a
longer neck, a brighter-colored shell. Expanding this
tree has been the painstaking work of generations of
naturalists, biologists, taxonomists and paleontolo-
gists during the 150 years since Darwin published
his seminal book.

Now that slow slog has quickened to an all-out sprint.

Rather than divining clues to an organism's evolution-
ary history from observed traits, scientists are going
straight to the genetic ledger sheet. Modern tools for
rapidly reading species' DNA are laying bare those
species' genetic inheritances, the patterns of genetic
code shaped by eons of mutation and natural selection.

And ever more powerful computers are churning
through gigabytes and gigabytes of this genetic data
to decipher which species are like sisters and which
are only distant cousins.

"We've really learned more about relationships
[among species] in the last 10 years than we did in
the previous 200 years," says Doug Soltis, an evolu-
tionary biologist at the University of Florida in
Gainesville. "This is definitely going to be viewed
as a golden era in our study of biodiversity. And
it's just now taking off."

Already, large branches of the tree are being redrawn
as scientists compare the DNA of dozens or hundreds
of distantly related species. Within years, rather than
decades, this computational excavation of life's past
will achieve an important milestone in the history of
science: a highly accurate map of the major branches
in Darwin's tree of life.

"It's Darwin come full circle," Soltis says. "Starting
from his tree figure [in the Origin], we're now put-
ting together a basic tree of life for a large portion
of known species. It's just incredibly exciting."


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A Most Private Evolution
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Dumb Designs for Sex: Evolutionary biology walks on
the weird side.


Trying to understand counterintuitive sexual parts and
habits follows in the best of scientific traditions. As
Charles Darwin worked up his ideas on evolution, he
pondered male phenomena that looked useless, or even
harmful, for surviving. Outsized horns on male beetles
puzzled him, as did male birds with gorgeous plumage.

Out of this consternation came his insight into a process
he called sexual selection, which he distinguished from
natural selection. There may be survival of the fittest,
but there's also survival of the sexiest.

Today the sex-related selection process doesn't get much
attention outside scientific circles, but it's a powerful
tool for making sense of downright peculiar stuff. Arnq-
vist and other biologists are expanding Darwin's frame-
work, exploring the counterintuitive aspects of sex from
flirtation to family life. And theorists are discussing fe-
male behavior that Darwin never recognized, or perhaps
just didn't care to discuss in print.

Not-so-natural selection

When Darwin first put his full idea of natural selection
into print, he knew it wasn't enough.

In 1859, he argued in On the Origin of Species that org-
anisms best adapted to their environment survive in
greater numbers and leave more offspring than do their
less fit neighbors. Thus more suitable traits gradually
replace clunkier versions.

Yet antlers on stags and tails on peacocks could hardly
be adaptations to the environment. Both antlers and tails
may be so familiar that it takes a minute to summon a
sense of their absurdity. They're huge. They must drain
energy to produce. There's no way they improve agility
in locomotion or foraging.

"The sight of a feather in a peacock's tail, whenever
I gaze at it, makes me sick!" Darwin wrote in a letter
to the botanist Asa Gray, albeit in a whimsical paragraph.
Nauseated or not, Darwin was willing to step beyond
survival of the fittest.

He devoted a few pages in the Origin to introduce sex-
ual selection as a sort of wild oats younger brother of
natural selection. Sexual selection, as Darwin formu-
lated it in the sixth edition of Origin, depends "not on
the struggle for existence in relation to other organic
beings or to external conditions, but on a struggle
between the individuals of one sex, generally the
males, for possession of the other."

[insert -- the degree to which it's a male struggle for
females -or- a female struggle for males, -or- both,
varies from species to species; in homo sapiens, the
additional element of cultural evolution is in play,
interlocked with evolutionary struggles on genetic,
sexual, and memetic levels (see Richard Dawkins'
discussion of the 'meme') -- end insert]


- - - end excerpts - - -