class="mine">This entire article (read it!) seems to do more justice to the science of Evolution, without having to give equal weight tothe mysticism of Inteligent Creationism. mjh
New Analyses Bolster Central Tenets of Evolution Theory
By Rick Weiss and David Brown, Washington Post Staff Writers
That a mechanism driven by random events should result in perfectly
adapted organisms — and so many different types — seems illogical.
“Even today a good many distinguished minds seem unable to
accept or even to understand that from a source of noise, natural selection alone and unaided could have drawn all the music of the
biosphere,” Jacques Monod, a French biologist and Nobel Prize winner, wrote in 1970 in the book “Chance and Necessity.”
Natural
selection was really hard to accept in Darwin’s day. But it has become easier with the discovery of genes, DNA and techniques that have
made it possible to watch natural selection happen. …
DNA is a stringlike molecule made up of paired beads called nucleotides.
It carries the instructions for making proteins and RNA, the chief building materials of life. Individually, these instructions are
called genes.
The random changes Darwin knew must be happening are accidents that happen to DNA and genes. Today, they can be
documented and catalogued in real time, inside cells.
Cells sometimes make errors when they copy their DNA before dividing. These
mutations can disable a gene — or change its action. Occasionally cells also duplicate an entire gene by mistake, providing offspring
with two copies instead of one. Both these events provide raw material for new genes with new and potentially useful functions — and
ultimately raw material for new organisms and species.
Richard E. Lenski, a biologist at Michigan State University, has been
following 12 cultures of the bacterium Escherichia coli since 1988, comprising more than 25,000 generations. All 12 cultures were
genetically identical at the start. For years he gave each the same daily stress: six hours of food (glucose) and 18 hours of starvation.
All 12 strains adapted to this by becoming faster consumers of glucose and developing bigger cell size than their 1988 “parents.” …
When Lenski and his colleagues examined each strain’s genes, they found that the strains had not acquired the same mutations.
Instead, there was some variety in the happy accidents that had allowed each culture to survive. And when the 12 strains were then
subjected to a different stress — a new food source — they did not fare equally well. In some, the changes from the first round of
adaptation stood in the way of adaptation to the new conditions. The 12 strains had started to diverge, taking the first evolutionary
steps that might eventually make them different species — just as Darwin and Wallace predicted.
In fact, one of the more exciting
developments in biology in the past 25 years has been how much DNA alone can teach about the evolutionary history of life on Earth. …
As scientists have identified the totality of DNA — the genomes — of many species, they have unearthed the molecular equivalent
of the fossil record.
It is now clear from fossil and molecular evidence that certain patterns of growth in multicellular
organisms appeared about 600 million years ago. Those patterns proved so useful that versions of the genes governing them are carried by
nearly every species that has arisen since.