Naturalistic Origins and Evolution of Life (2 of 3)
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First Evidence That Comets Filled The Oceans:
A Dying Comet's Kin May Have Nourished Life On Earth
Date: Posted 5/21/2001
Excerpt: "The idea that comets seeded life on Earth with water
and essential molecular building blocks is hotly debated, and
for the first time, we have seen a comet with the right compo-
sition to do the job," said Dr. Michael Mumma of NASA's
Goddard Space Flight Center.
... A separate announcement ... is a unique observation that
reveals just how much water comets of this type can carry.
LINEAR, with a nucleus estimated at 2,500 to 3,300 feet (about
750 to 1,000 meters) in diameter, carried about 3.6 million tons
(3.3 billion kilograms) of water within its bulk
... Using telescopes sensitive to infrared light, Mumma and a
team of astronomers studied comet LINEAR before its dramatic
breakup last July and determined that its unusual chemistry
points to an origin near Jupiter's orbit. Comets that formed in
this region are expected to have the same ratio of normal water
to "heavy" water as found in Earth's oceans.
... comets that formed near Jupiter are rare today, but they
would have been in the majority during the solar system's forma-
tion, simply because the Jupiter orbit region had most of the
material in the pre-planetary gas and dust cloud. Therefore,
scientists expect that the primordial Earth would have inter-
cepted more comets formed near Jupiter's region than those
Because Jupiter's region was closer to the Sun than the other
gas giant planets, it received more light and was warmer, so
more reactions occurred in the gas. Thus, greater amounts
of complex organic molecules were available to wind up in
a comet. Also, Jupiter's powerful gravity kept collision speeds
between comets near it high, preventing them from growing
very large. Both factors may have given a boost to life on
"It's like being hit by a snowball instead of an iceberg," said
Mumma. "The smaller comets from Jupiter's region impacted
Earth relatively gently, shattering high in the atmosphere and
delivering most of their organic molecules intact. Also, these
comets would have had a greater portion of life's building
blocks -- the complex organic molecules -- to begin with.
This means life on Earth did not have to start completely
from scratch. Instead, it was delivered in kit form from
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Study Offers Insights Into Evolutionary Origins Of Life
Date: Posted 5/18/2001
Excerpt: In some of the strongest evidence yet to support the
RNA world-an era in early evolution when life forms depended
on RNA-scientists at the Whitehead Institute for Biomedical
Research have created an RNA catalyst, or a ribozyme, that
possesses some of the key properties needed to sustain life in
such a world.
... These results, described in the May 18 issue of Science, sug-
gest that RNA could have had the ability to replicate itself and
sustain life in early evolution, before the advent of DNA and
The findings will ultimately help evolutionary biologists address
questions about how life began on earth more than three billion
... Theories about the origins of life have long intrigued scientists
and lay people alike. "A fundamental question about the origin of
life is what class of molecules gave rise to some of the earliest life
forms?" says Bartel.
... "We will never be able to prove the existence of the RNA
world because we can't go back in time-but we can examine
the basic properties of RNA and see if these are compatible
within the RNA world scenario," says Bartel.
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How Did We Get So Smart? Study Sheds Light
On Evolution Of The Brain
Date: Posted 5/10/2001
Excerpt: Princeton and Bell Labs scientists have devised
a simple but powerful method for analyzing brain anatomy,
providing the first reliable measure of how brains of humans
and other mammals are related to one another across evolu-
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Natural Selection Drives Rapid Evolution Of Female
(as Well As Male) Reproductive Proteins In Mammals,
Cornell Study Finds
Date: Posted 3/9/2001
Excerpt: Chemical signals at the most critical moment for new
life in mammals -- when sperm meets egg and attempts fertiliza-
tion -- evolve rapidly in a process driven by positive Darwinian
selection, according to a Cornell University study.
... Moreover, the subtle but significant changes in signaling pro-
teins of sperm and eggs could turn out to be an "engine of spe-
ciation," Aquadro says, referring to the origin of new species
Just a few changes in amino acid sequences in recognition of
surface proteins may be enough to make egg and sperm proteins
incompatible, he notes. One of the distinguishing marks of dif-
ferent species is that they cannot cross-reproduce. The study
of the evolution of reproductive proteins might thus provide
important insight into how new species arise. ...
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Parasite's Sperm-Encryption Keeps Species Apart
Date: Posted 2/8/2001
Excerpt: Scientists have found the most convincing evidence
yet that a parasite can contribute to splitting a species in two,
thanks to a phenomenon where a wasp's damaged sperm can
be "rescued" or fixed only by mating with particular females.
... "This is the best evidence of a parasite contributing to specia-
tion that we've seen," says Werren. "Splitting a species in two
is probably just a side effect of the bacteria's reproductive
method, of their way of eliminating non-infected hosts."
A consequence of this method of eliminating the non-infected
appears to be that the host species is more susceptible to split-
ting into two species. The two species of wasp that Werren
studied can actually interbreed if given an antibiotic to kill the
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NASA Scientists Find Clues That
Life Began In Deep Space
Date: Posted 1/31/2001
Excerpt: Duplicating the harsh conditions of cold interstellar
space in their laboratory, NASA scientists have created primi-
tive cells that mimic the membranous structures found in all
living things. These chemical compounds may have played
a part in the origin of life.
"Scientists believe the molecules needed to make a cell's mem-
brane, and thus for the origin of life, are all over space. This
discovery implies that life could be everywhere in the universe,"
said Dr. Louis Allamandola.
... Using simple, everyday chemicals, researchers from Ames'
Astrochemistry Laboratory and the Department of Chemistry
and Biochemistry at the University of California, Santa Cruz,
have created, for the first time, "proto"-cells. These are the
primitive cells that mimic the membranous structures found
in all life forms. "This process happens all the time in the dense
molecular clouds of space," Allamandola said.
... "The formation of these biologically interesting compounds
by irradiating simple interstellar ices shows that some of the
organics falling to Earth in meteorites and interplanetary dust
might have been born in the coldest regions of interstellar
space," Allamandola said. "The delivery of these compounds
could well have been critical to the origin of life on Earth."
... Scientists do not yet know whether life began as naked
RNA or as genetic material encapsulated in membranes. But
at some point, membranes became important.
"All life as we know it on Earth uses membrane structures
to separate and protect the chemistry involved in the life
process from the outside," said Dr. Jason Dworkin of the
SETI Institute, the paper's lead author and a team member.
"All known biology uses membranes to capture and generate
"Membranes are like a house," Dworkin added. "Maybe these
molecules were just the raw lumber lying around that allowed
origin-of-life chemicals to move in and set up housekeeping
or construct their own houses."
... this new work shows that the early chemical steps believed
to be important for the origin of life do not require an already-
formed planet. Instead, they seem to take place in deep space
long before planet formation occurs.
This implies that the vastness of space is filled with chemical
compounds which, if they land in a hospitable environment
like our Earth, can readily jump-start life. ...
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Biologists Uncover Darwin's "Missing Evidence" For
Divergence Of Species In A Warbler's Song
Date: Posted 1/19/2001
Excerpt: Biologists at the University of California, San Diego
have demonstrated, in a study of the songs and genetics of a
series of interbreeding populations of warblers in central Asia,
how one species can diverge into two.
Their description of the intermediate forms of two reproductively
isolated populations of songbirds that no longer interbreed is the
"missing evidence" that Darwin had hoped to use to support his
theory of natural selection, but was never able to find.
"One of the largest mysteries remaining in evolutionary biology
is exactly how one species can gradually diverge into two," says
Darren E. Irwin, a biologist at UCSD who headed the study,
detailed in the January 18 issue of the journal Nature.
"This process, known as speciation, is very difficult to study
because it can take a great deal of time to occur."
... "The greenish warbler is the first case in which we can see all
the steps that occurred in the behavioral divergence of two species
from their common ancestor. These results demonstrate how small
evolutionary changes can lead to the differences that cause repro-
ductive isolation between species, just as Darwin envisioned.
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Study Illustrates Diversification, Speciation
In Biological "Islands"
Date: Posted 12/15/2000
Excerpt: Lizard species on large Caribbean islands are more
numerous than those on smaller islands because there is more
evolution going on. The bigger the island, the faster species pro-
liferate and diversify.
... "When you focus on the larger islands, the rate of speciation
is a function of island area," said Losos. "A large island equals
more speciation events. At some level this is intuitive, but it has
never been demonstrated before that differences in the rate of
speciation, of evolution, can produce the species-area relation-
... "There is simply more opportunity for isolation to occur and
for species to diverge on larger islands," said Losos.
The classic explanation of how speciation occurs is that one
species gets separated into two or more geographically isolated
groups, between which there is no genetic contact.
They are therefore geographically and genetically isolated; they
are not interbreeding. Over time, the groups diverge so that even
if the geographic barrier that caused the isolation was removed,
they are now separate species and cannot interbreed.
An unexpected finding reported by Losos and Schluter is the
existence of an island area threshold of 3000 square kilometers
(roughly 1,800 square miles), below which speciation does not
occur. It is only on the four largest Caribbean islands that there
is evidence of speciation. ...
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Scientists Find Gene That Fuels "Sexual Arms Race"
Date: Posted 12/1/2000
... thanks to the lowly fruit fly and a team of scientists at the
University of Wisconsin-Madison and at Washington Uni-
versity in St. Louis, one genetic circuit that governs sexual
dimorphism - the diagnostic differences between the sexes -
has been found and characterized.
The discovery, described in the Thursday, Nov. 30, edition
of the British scientific journal Nature, is important because
it not only shows how and why animals dress for reproduc-
tive success, but provides a glimpse of the genetic changes
that, over time, lead to the evolution of new animal species.
"Fundamentally, the difference between species is in their
DNA," says Sean B. Carroll. ... "And this genetic circuit holds
the gene that makes a key difference between fly species."
In the fruit fly, specifically the laboratory workhorse Droso-
phila melanogaster, one of the obvious visual signals of its
sex is body pigmentation: the rear end of the melanogaster
male is heavily pigmented and the female's is not. This new
"fruit fly fashion" has evolved only recently in a relatively
small subset of Drosophila species.
... The researchers found that a gene called "bric-a-brac"
establishes the difference between melanogaster females and
males by suppressing pigmentation in females. However, the
same gene functions in both sexes in other fly species where
male-specific pigmentation is absent and males and females
look pretty much the same.
Beginning with Darwin, scientists have believed that ani-
mals assume gaudy colors to promote themselves as poten-
tial mates, and that this dressing up is a major force in animal
The present role of bric-a-brac, says Carroll, has probably
been shaped by the process of "sexual selection" because
the pigmentation patterns specified by this gene affect mating
But in investigations of the genetic controls for gender-based
pigmentation in fruit flies, the HHMI team at Wisconsin found
that, for the female, the sex appeal of a pattern or color wears
off over time.
In experiments with male flies engineered to have the same
abdominal stripes as the female melanogaster, the courted
females were smitten no less than when confronted with a
male flying all the colors of machismo.
According to Kopp, what this suggests is that the male is
constantly under pressure to evolve something new in order
to stay competitive in the mating game. It is very much a
sexual arms race, he says.
"What we found was that the female didn't care, and that
makes sense under the arms race scenario," says Kopp.
"The pigmentation has lost its significance to the female
- it is last year's fashion - and males are probably forced
to evolve new ones all the time."
Accumulated over time, it is these kinds of wardrobe chan-
ges that lead to morphological evolution and the establish-
ment of new species, Carroll argues.
... the fundamental importance of the new discovery, Carroll
maintains, is that it provides a window to ongoing evolutionary
"Looking at these flies, we could see that this is something
that evolved very quickly, and that it continues to evolve,"
says Kopp. "Such rapid change give us a chance to observe
evolution in progress, rather than just look at the end result."
"It's like going from a vacation post card to a home video,"
says Carroll. "We've captured a genetic event responsible
for morphological change and we're beginning to understand
how changes at the molecular level affect development and
translate into the diversity of forms we see around us."
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Astrobiologists Probe A Desert Galapagos
To See Evolution's Great Leap
Date: Posted 10/24/2000
Excerpt: It is the most remarkable and important time in the
history of life on Earth -- 540 million years ago, when 3 billion
years of simple, single-celled life reached a dramatic turning
point, and life evolved into a wide variety of multi-cellular
It was a planetary biological event that is known as the Cambrian
Transition and is sometimes even called "the Cambrian Explosion."
"All hell broke loose in evolution," said Arizona State University
biologist James Elser. "All kinds of new multi-cellular life forms
arose in all the major groups."
"It was a huge, huge event in the biosphere," added ASU paleon-
tologist and astrobiologist Jack Farmer. "We switched over from
a microbially dominated world to one that included large, multi-
celled animals and plants -- large macroscopic organisms.
It was an evolutionary event that changed whole ecosystems.
Suddenly the biosphere added herbivores and carnivores to eco-
systems where none had ever existed before. This meant that all
the ecosystem dynamics -- energy flow processes and so on --
underwent a radical change."
"It's probably the most important event in the history of life and
we don't really understand why it happened," Elser pointed out.
"Though there are lots of ideas about what might have occurred."
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New Species Arise More Quickly Than
Previously Believed, UMass Researcher Finds
Date: Posted 10/20/2000
Excerpt: The splitting of a species into two new species may
occur in far fewer generations than scientists previously believed ...
"There is a widely-held perception that when one population splits
into two different environments, traits evolve quickly and, as a
result, the two new populations become less likely to interbreed.
That is, they become reproductively isolated.
This process, called ecological speciation, may be one of the easi-
est and fastest ways that new species arise. Our results suggest
that this perception may not only be correct, but in spades," said
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New Theory On The Mystery Of The Origin Of
Life Proposed By Weizmann Institute Scientists
Date: Posted 6/8/2000
Excerpt: One of the greatest mysteries, which continuously
fascinates many scientists worldwide, concerns the way by
which life emerged on primeval Earth.
The accepted notion is that prior to the appearance of living
organisms, there was a stage of chemical evolution, which
involved selection within inanimate chemical mixtures. This
is thought to have eventually led to the crucial moment, when
self-replicating molecules arose.
As self-replication is a most fundamental characteristic of
living entities, such an event is often defined as the birth of
Self-replication of molecular systems is often viewed in the
context of information content. Many scientists believe that
life began with the spontaneous emergence of biopolymers,
such as proteins or RNA, where information is stored in the
sequence of chemical units.
Experiments mimicking the conditions on Earth billions of
years ago have shown how such chemical units, e.g. some
of the building blocks of proteins and RNA, could appear
spontaneously. Yet, the emergence of proteins or self-
replicating RNA molecules remained enigmatic.
This started a journey leading to alternatives to proteins and
RNA, ... a new route for the origin of life, based on lipid
... Lipids are oily substances, known as chief ingredients
of the cell's membranes. Lipids have two different aspects
- one hydrophilic (water-attracting), and the other hydro-
phobic (water-repelling). They get readily synthesized under
simulated prebiological conditions. ...
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Gene Tug-Of-War Leads To Distinct Species
Date: Posted 5/3/2000
Excerpt: By crossing two mouse species that normally do not
interbreed, Howard Hughes Medical Institute (HHMI) researchers
have gained a better understanding of how gene imprinting can
influence the establishment of distinct species.
The majority of mammalian genes are present in two copies that
are expressed and regulated. A small number of mammalian genes,
however, are subject to special regulation by a process called gene
The imprint is a chemical mark attached to genes during egg or
sperm development. Imprinting physically marks a gene in such
a way that the parental origin of the gene can be distinguished
and expressed accordingly.
Most imprinted genes seem to govern fetal growth regulation,
explained Shirley M. Tilghman, an HHMI investigator at Princeton
University. Some researchers speculate that imprinting evolved in
order to establish boundaries between species. Imprinting is also
thought to provide a barrier to unisexual reproduction and the
interbreeding of species. ...
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New Calculations Show Life's Origins
Possible In Volcanic Gases
Date: Posted 3/28/2000
Excerpt: Geologists at Washington University in St. Louis have
developed new theoretical calculations on how life might have
arisen on Earth, Mars and other celestial bodies from volcanic
... higher initial temperatures of spewing volcanic gases are more
favorable for organic synthesis, once the gases dilute and cool to
the hydrocarbon-forming zone of 150-300 degrees C.
"These conditions might have contributed to the production of
organic compounds required for the emergence of life," says
Shock, who first rose to prominence in the "Origins of Life"
debate in 1992 when he performed calculations that showed life
could have first emerged chemosynthetically -- without sunlight --
at hot water vents on the ocean floor.
... As for the origins of life -- on Earth, at least -- there are two
basic competing views: One suggests that life was brought here
by comet or meteorite impacts or interplanetary dust; the other
that life was generated here, either at the ocean floor, through
a lightning spark that touched off an atmosphere that produced
organic compounds in watery environments, or in volcanic
gases. All scenarios involve organic compounds.
"Unlike spark discharge scenarios, the processes we are pur-
suing to study the origins of life, here, or on Mars, are normal,
daily geological processes. The volcanic gas scenario is one
of the most approachable,' says Shock. "The evidence is readily
accessible, and we know we can extrapolate from evidence here
to Mars and other bodies without much ambiguity."
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Forest Edges Critical To Evolution Of New Species
Date: Posted 11/24/1999
Excerpt: New Research Bolsters Theory That Forest Edges
Are Hotbeds of Speciation, Kicking Off Global Investigation
Of Evolutionary Processes In Tropical Rainforests ..."
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Really Rapid Evolution: Water Pollution Prompts
Crustaceans To Adapt In A Hurry, Cornell And
Max-Planck Biologists Discover
Date: Posted 9/30/1999
Excerpt: When the going gets toxic, the hungry get clever -- very
... "It appears that ecological events that we think of as occurring
relatively quickly -- such as nutrient enrichment of a lake -- can
be influenced by the rapid evolution of the animals that are affect-
ed," says Hairston, a professor of environmental science. "If these
little crustaceans hadn't changed with the times, their kind might
not have survived."
... In less than 30 years, as Germany's Lake Constance suffered
environmental degradation from phosphorus pollution, populations
of tiny crustaceans called Daphnia found more and more toxic
cyanobacteria (also called "blue-green algae") mixed with their
favorite food, a more edible type of algae.
So the crustaceans adapted to handle a less nutritious food that
would have seriously stunted the growth of their ancestors, and
they became one of the important, natural controls for toxic
cyanobacteria in the lake.
... Strong natural selection can lead to rapid changes in organisms,
which can, in turn, influence ecosystem processes," the biologists
concluded in their article. ...
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Team Of 200 Scientists Presents New Research
That Reveals Full "Tree Of Life" For Plants
Date: Posted 8/6/1999
Excerpt: A five-year effort to reconstruct the evolutionary rela-
tionships among all of Earth's green plants has resulted in the
most complete 'tree of life' of any group of living things on the
planet, scientists announced today.
The team has revealed that the group traditionally thought of
as 'plants' is really four separate lineages or 'kingdoms,' with
one group -- fungi -- being more related to animals than to plants.
... The team has clarified the plant 'kingdoms' and their relation-
ships to animals. There are five main trunks, or lineages, of
complex, "nucleated" organisms on the Earth's genealogical
tree, four of which are classified as plants. They include the
green plants, the brown plants, the red plants, the fungi, and
... "We can't really think of life on earth in terms of only the
'animal kingdom' and the 'plant kingdom' anymore," said Mishler.
"In fact, there are five kingdoms of complex organisms on Earth
today. One of the kingdoms, fungi, are more related to animals
than to plants. This means that the mushrooms you eat are more
related to you than to the tree on which they are growing."
The team's work has resulted in a new understanding of how
the explosion of plant life on the Earth's lands occurred. All
life first arose in the ocean, then some life moved to freshwater
and a number of lineages went back to the sea. It was the life
forms that moved to freshwater that spawned the land plants
we know of today.
... The team's research shows that all the plants and animals
together form only a small branch on the tree of life, indicat-
ing that there is a universe of mostly single-celled, and poorly
known organisms that make up the most substantial parts of
Centuries ago, the scientific discovery that the sun is merely
one star in a universe full of stars, planets and other astral
bodies shattered mankind's preconceptions of space and led
to the exploration of the cosmos.
Similarly, the research team's findings could shatter some
preconceptions about life here on Earth by proving that all
the familiar biodiversity (including humans, along with the
other animals and plants), are only one "tiny twig" on the
tree of life on Earth.
The team has traced how the most basic of one-cell, bacteria-
like organisms that had neither nuclei nor chromosomes
"merged" with each other to become not only multi-cellular
but also multi-functional.
Although life on this planet has evolved to an astonishing level
of richness and complexity in the form of plants and animals,
most of the Earth's life forms are still found in these ancient
bacteria-like organisms, according to Mishler. The majority
of these organisms have not been identified.
To date, scientists have identified about 1.4 million species
of organisms on earth, and estimates of the numbers of undis-
covered and undescribed species of organisms range from
10 million to more than 100 million.
"There are millions of microscopic organisms that live on
and in plants and animals and in the soil, air, and water," said
Mishler. "They remain largely unexplored. Although some
progress has been made, scientists are only just beginning
to bring these creatures under the microscope much less to
understand exactly how they interact with plant and animal
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in post 3 of 3)
in this series:
of Evidence for Naturalistic
Origins and Evolution of Life (1 of 3)
of Evidence for Naturalistic
Origins and Evolution of Life (2 of 3)
of Evidence for Naturalistic
Origins and Evolution of Life (3 of 3)
of Evidence for Naturalistic
Origins and Evolution of Life (expanded - 4 of 4)
- - - Additional Information of Relevance - - -
Origins of Energy, Matter, Space, Time, and Life (1 of 2)
of Energy, Matter, Space, Time, and Life (2 of 2)
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