Archive
of Past Articles for Chapter 3
29 June 2007. Study
Traces Cat’s Ancestry
to Middle East. By Nicholas Wade. The New
York Times. Excerpt: … [Carlos
A. Driscoll of the National
Cancer Institute and his colleagues
have] spent more than six years collecting
species of wildcat in places as far apart
as Scotland, Israel, Namibia and Mongolia.
He then analyzed the DNA of the wildcats
and of many house cats and fancy cats.
Five subspecies of wildcat are distributed
across the Old World. … Their
patterns of DNA fall into five clusters. The
DNA of all house cats and fancy cats falls
within the Near Eastern wildcat cluster, making
clear that this subspecies is their ancestor… Wheat,
rye and barley had been domesticated in the
Near East by 10,000 years ago, so it seems
likely that the granaries of early Neolithic
villages harbored mice and rats, and that
the settlers welcomed the cats’ help
in controlling them. Unlike other domestic
animals, which were tamed by people, cats
probably domesticated themselves, which could
account for the haughty independence of their
descendants. … Until recently the
cat was commonly believed to have been domesticated
in ancient Egypt, where it was a cult animal.
But three years ago a group of French archaeologists
led by Jean-Denis Vigne discovered the remains
of an 8-month-old cat buried with its human
owner at a Neolithic site in Cyprus. …
26 June 2007. Fast-Reproducing
Microbes Provide a Window on Natural Selection. The New York
Times. By Carl Zimmer. Excerpt:
In the corner of a laboratory at Michigan
State University, one of the longest-running
experiments in evolution is quietly unfolding.
A dozen flasks of sugary broth swirl on a
gently rocking table. Each is home to hundreds
of millions of Escherichia coli, the common
gut microbe. These 12 lines of bacteria have
been reproducing since 1989, when the biologist
Richard E. Lenski bred them from a single
E. coli. “I originally thought it might
go a couple thousand generations, but it’s
kept going and stayed interesting,” Dr.
Lenski said. He is up to 40,000 generations
now, and counting. In that time, the bacteria
have changed significantly. For one thing,
they are bigger — twice as big on average
as their common ancestor. They are also far
better at reproducing in these flasks, dividing
70 percent faster than their ancestor. These
changes have emerged through spontaneous mutations
and natural selection, and Dr. Lenski and
his colleagues have been able to watch them
unfold.
When Dr. Lenski began his experiment 18 years ago, only a few
scientists believed they could observe evolution so closely.
Today evolutionary experiments on microbes are under way in many
laboratories. And thanks to the falling price of genome-sequencing
technology, scientists can now zero in on the precise genetic
changes that unfold during evolution, a power previous generations
of researchers only dreamed of. In the past century scientists
have gathered a wealth of evidence about the power of natural
selection. But much of that evidence has been indirect. In the
late 1980s a few scientists began experimenting with microbes,
hoping to observe natural selection in something closer to real
time. Microbes can reproduce several times a day, and a billion
of them can fit comfortably in a flask. Scientists can carefully
control the conditions in which the microbes live, setting up
different kinds of evolutionary pressures. Within a few hundred
generations, Dr. Lenski was seeing changes, and the bacteria
have been changing ever since. The microbes have adapted to their
environment, reproducing faster and faster over the years. One
striking lesson of the experiment is that evolution often follows
the same path. “We’ve found a lot of parallel changes,” Dr.
Lenski said. … Scientists have long known that underlying
these visible changes were genetic ones. But only now are they
documenting the mutations that allow this evolution to happen
in the first place. …
26 June 2007. From
a Few Genes, Life’s
Myriad Shapes. The New York Times. By Carol
Kaesuk Yoon. Excerpt:
Since its humble beginnings as a single cell,
life has evolved into a spectacular array
of shapes and sizes... But just how such diversity
of form could arise out of evolution’s mess of random genetic
mutations … has remained one of the
most fascinating and intractable questions
in evolutionary biology. Now finally, after
more than a century of puzzling, scientists
are finding answers coming fast and furious
and from a surprising quarter, the field known
as evo-devo. Just coming into its own as a
science, evo-devo is the combined study of
evolution and development, the process by
which a nubbin of a fertilized egg transforms
into a full-fledged adult. And what these
scientists are finding is that development,
a process that has for more than half a century
been largely ignored in the study of evolution,
appears to have been one of the major forces
shaping the history of life on earth. For
starters, evo-devo researchers are finding
that the evolution of complex new forms, rather
than requiring many new mutations or many
new genes as had long been thought, can instead
be accomplished by a much simpler process
requiring no more than tweaks to already existing
genes and developmental plans. “We’re
still a very young field,” Dr. Gilbert
said. “But I think this is a new evolutionary
synthesis, an emerging evolutionary synthesis.
I think we’re seeing it.”
26 June 2007. The
Human Family Tree Has Become a Bush With Many
Branches.
By John Noble Wilford. The New York Times. Excerpt:
Time was, fossils and a few stone artifacts
were about the only means scientists had of
tracing the lines of early human evolution.
And gaps in such material evidence were frustratingly
wide. When molecular biologists joined the investigation
some 30 years ago, their techniques of genetic
analysis yielded striking ...
26 June 2007. Darwin
Still Rules, but Some Biologists Dream of
a Paradigm Shift. By Douglas
H. Erwin. The New York Times. Excerpt: É Paradigm
shifts are the stuff of scientific revolutions.
They change how we view the world, the sorts
of questions that scientists consider worth
asking, and even how we do science. The discovery
of DNA marked one such shift, the theory of
plate tectonics another. Éour evolutionary
framework ... was constructed from the 1930s
to 1950s by early geneticists, paleontologists
and others, who disagreed about the efficacy
of natural selection in driving evolutionary
change (Darwin's big idea) and about the nature
of the underlying genetic variation upon which
natural selection could act. What they came
to agree on was called the modern synthesis Éthat
mutations to DNA create new variants of existing
genes within a species. Natural selection,
driven by competition for resources, allows
the best-adapted individuals to produce the
most surviving offspring. So adaptive variants
of genes become more common. ÉIn the
past few years every element of this paradigm
has been attacked. Concerns about the sources
of evolutionary innovation and discoveries
about how DNA evolves have led some to propose
that mutations, not selection, drive much
of evolution, or at least the main episodes
of innovation, like the origin of major animal
groups, including vertebrates. The Achilles'
heel of the modern synthesis, as noted by
the philosopher Ron Amundson, is that it deals
primarily with the transmission of genes from
one generation to the next, but not how genes
produce bodies. The failure to consider
how biodiversity grows reflects an even more
troubling flaw in the modern synthesis: it
lacks any real sense of history. ÉMost
species modify their environment and this
often changes how selection affects them:
they construct, at least in part, their own
environment. As evolutionary biologists we
have little understanding of what these processes
mean for evolution.
Does all this add up to a new modern synthesis?
There is certainly no consensus among evolutionary
biologists, but development, ecology, genetics
and paleontology all provide new perspectives
on how evolution operates, and how we should
study it....
4 December 2006. The
American Geological Society website about
American education and the topic of evolution.
Archive of Past Articles for Chapter 3
