Reflectorites
Here are excerpts from BBC & Electronic Telegraph science pages
for the period 4-11 May 2000, with my comments in square brackets.
Steve
=====================================================
http://news.bbc.co.uk/hi/english/sci/tech/newsid_745000/745080.stm BBC
Thursday, 11 May, 2000 ... UK Fossils may be 'first Europeans' ... The
Remains of what may be the earliest human ancestors to migrate from
Africa into Europe have been found in the Republic of Georgia. Two
skulls, which are probably about 1.7 million years old, were unearthed
during an archaeological dig at a medieval castle at Dmanisi. They were
discovered alongside stone tools and the bones of animals. One of the
skulls is nearly complete; of the other, only the skullcap has survived. The
fossils suggest that early humans moved out of Africa hundreds of
thousands of years earlier than previously thought. They also put a
question mark against the assumption that sophisticated stone tool
technology was required for migration ... The age and skeletal
characteristics of the Dmanisi skulls link them to the early humans who
lived in East Africa at the same time known as Homo ergaster. This
creature was a less developed hominid than Homo erectus that many
thought was the first to move out of Africa to populate Asia and Europe.
H. erectus had more sophisticated technology than H. ergaster ... a form of
advanced tool kit known as the "Acheulean," or "hand-axe" tradition. ...
the stone tools found with the Dmanisi fossils are of the less sophisticated
"Oldowan" or "pebble-chopper" type that preceded Acheulean technology.
...Dr Chris Stringer ...an expert on the "Out of Africa" theory of modern
human origins ... is doubtful the Dmanisi hominids were our direct
ancestors... "We're descended from similar people who stayed in Africa.
Africa in a sense kept pumping out migrations and dispersals of people and
this included people like the Neanderthals who, equally, it doesn't seem
were our ancestors. "The ancestors of modern humans may have left Africa
only in the last 100,000 years." [IMHO a helpful setting of this Georgia
find in the overall context of the origin of modern humans. ]
http://www.telegraph.co.uk/et?ac=000113078204876&rtmo=aqhhhJTJ&atmo=KKKKKKKM&pg=/et/00/5/11/ecfmot11.html
Electronic Telegraph. 11-05-00 ... This is what drives you Learning from
the motors that cruise a cell's highways will have revolutionary
consequences ... AS you read these words
eyes precisely across the page. Others are whirring within your brain to
enable you to think about this sentence. Many more are getting on with the
serious business of life itself, delivering heart beats, digesting food and
driving metabolism. Each one of your cells can be thought of as a
metropolis within which these motors trundle about. Millions dart hither
and thither along the cellular equivalent of roads at speeds approaching 18
millimetres per hour. They come in more shapes and styles than the cars in
London: some go "forward", some "backwards". Others glide and skip.
There are even some that do cartwheels. They stop, start, speed up and
slow down in response to still unknown traffic signals. Amid this bustle,
motors hold the cell in shape, orchestrate the movement of genetic material
- DNA and help import nutrients and export wastes. Others lug packages
of messenger chemicals along nerves. During cell division, the network of
routes is rebuilt ... "As we learn more about these molecular motors they
have become more familiar and less magical," .... And yet much of the
mystery remains, notably in the awesome efficiency of these motors and the
way they are customised for each use. ... The motors are proteins, which
consist of long strings of amino acids, arranged in sheets, spirals (helices)
and other complex shapes. ... Just as a car's engine burns petrol to push the
vehicle along, molecular motors harness energy from chemical reactions.
The petrol is a ubiquitous molecule called ATP. ... The motors that cruise
the cell's highways come in three families. The first ... is myosin, which
makes muscle contract along rails of actin filament. The second ..., is
dynein. This cumbersome motor rattles along microtubules, flaps the fronds
(cilia) that motivate microorganisms, and links microtubules in the tails of
sperm, enabling them to wriggle... The third, kinesin .... transports
packages around inside cells including nerves - on rails called microtubules,
and plays a central role in cell division. Five years ago these three motors
looked very different. Now two of the three - myosin and kinesin - are
beginning to look very similar. They were originally put in separate families
for good reason. There are no similarities in their associated genetic
sequences, which describe the amino acid sequence within each protein.
The business end of kinesin is less than half the size of myosin's and seems
to work differently...The movements are different ... myosin and kinesin
share a core mechanism that converts chemical energy into movement....
"The big message is that myosins and kinesins are a good example of
nature's innovation: evolution has taken a single fundamental mechanism
and elaborated on it to come up with a wide range of molecules with very
different attributes," ... Despite the fact that the genetic codes for kinesin
and myosin are so different, "the central parts of these motors, where the
ATP is, were very similar," ... "You could overlap the structures on a
computer and they superimposed beautifully."...This suggests they all share
a common ancestor that evolved more than a billion years ago. No wonder
that molecular motors are so widespread. They appear in plants and fungi,
indeed any advanced cell ... The real differences between myosin and
kinesin lie in the parts of the motors that stick to the actin and microtubule
tracks. ... By studying these motors, scientists hope to uncover the
mechanisms of molecular movement,... Given the wonders routinely
performed by the machinery in a living cell, man-made molecular engines
could prove revolutionary. ... [A good example of how metaphysical
naturalists can look straight at design, even study it in detail for years, and
still not see it. Because naturalists' fundamental assumption is that `nature
is all there is', these molecular motors of "awesome efficiency", which far
exceed the capacity of human intelligent designers to make, are simply
assumed to be "a good example of nature's innovation: evolution has taken
a single fundamental mechanism and elaborated on it". How a `blind
watchmaker' could ever put together *three* such motors (remember
"there are no similarities in their ... genetic sequence") is not stated, nor is
how a cell could even exist in the first place without them?]
http://www.telegraph.co.uk/et?ac=000113078204876&rtmo=aqhhhJTJ&atmo=KKKKKKKM&pg=/et/00/5/11/ecntig11.html
Electronic Telegraph. 11-05-00 ... Extinct 'tiger' could live again by cloning
... SCIENTISTS hoping to bring the extinct Tasmanian tiger back to life
announced last week that they were within sight of their goal after samples
taken from a preserved pup were found to contain high quality DNA ...
The Australian Museum in Sydney has spent a year developing its cloning
project after a perfect specimen of a Tasmanian tiger pup was discovered in
a jar of alcohol. The Tasmanian tiger became extinct in 1936, but the
Australian scientists now believe that there is real hope that the creature
can be revived. They claim this is the first time that such high quality DNA
essential to the success of the scheme - has been extracted from an extinct
animal, and believe they are on course to achieve a world first. Prof
Michael Archer, the museum's director, described the project as "the
biological equivalent of human beings taking the first step on the moon".
He said: "I am committed to the view that within my lifetime I will see this
happen. There are some estimates it could be within 10 years. We would
like to see Australia overrun with this wonderful animal again." The pup
has been preserved since 1866, and last month tissue samples were taken
from the heart, liver, muscle and bone marrow for analysis. Dr Don
Colgan, head of the museum's evolutionary biology unit, said he was
confident that the work had provided his team with multiple copies of
nearly every Tasmanian tiger gene. One possible way forward is for the
genetic material to be inserted into the empty egg of a female of a similar
species, which could then incubate it. The success of the scientists will
depend largely on funding. It has been estimated that it will cost more than
þ25 million to bring the project to fruition. ... The Tasmanian tiger, or
thylacine, is in fact a marsupial wolf. It was given its name because of the
stripes on its back and tail. In July 1936, the Tasmanian state government
declared it a protected species, but the last known specimen died at Hobart
Zoo later that year. ... [My biology lecturer said this was technically
feasible, but the cost (about A$80M), could be better spent helping many
species not go extinct. There is also the possibility that the Thylacine is not
extinct-Tasmania has very rugged and inaccessible wilderness areas and
there have been periodic reports of sightings of animals vaguely fitting the
Thylacine's description.]
http://www.telegraph.co.uk/et?ac=000113078204876&rtmo=kNbbAk3p&atmo=99999dd9&pg=/et/00/5/4/ecnegg04.html
Electronic Telegraph. 0405-00 ... Gene switch eggs give infertile women
hope ... HUMAN eggs can now be "reconstituted" so that an infertile
woman can conceive with a donated ovum and still have a child that is her
descendant, ... The method allows doctors to introduce an infertile
woman's genetic make-up into a donated egg, so that the resulting child
carries her genes rather than the donor's. This approach could make it
easier for older women to have children. It also could offer treatments for
metabolic diseases, and enable women who are unable to make eggs to
reprogramme donor eggs with any of their body cells to create their own
eggs. The technique advances cloning research because parts of the method
resemble those used to create Dolly the sheep, however ...there are
important differences. Although the team's effort is not aimed at human
reproductive cloning, members believe that it could aid the development of
therapeutic cloning methods to grow a patient's own tissue ... no attempts
had been made to fertilise the reconstituted eggs because the creation of
human embryos for research was banned in France and Spain and strictly
regulated in Italy. One of the team ... is already at work in Brazil, where
ethical guidelines allow such studies. If no problems arise, such as embryo
abnormalities, ... it would be possible to use the technique on patients by
the end of the year, ... in Europe would probably take longer because of the
need to get ethical agreement. The techniques transfer the nucleus of an
egg from an infertile woman which contains her genetic make-up in the
form of chromosomes into a donor ovum from which the nucleus had been
removed, leaving only the genetic material in the mitochondria of the egg.
The reconstituted egg is then fertilised with sperm. In this way, the infertile
woman would give birth to a baby who would be almost entirely
genetically her own and her partner's. ... "Certain steps of our technique
may resemble some steps in cloning. However, it is distinctly different. I am
not in favour of human cloning and I don't want to take part in any
scientific investigation in this direction, especially not in humans. ... [More
dilemmas for the ethicists! If this does not involve the destruction of an
actual or potential human life, there may be no problem with it? However,
the child might have an identity or even a legal problem, because the
mtDNA is the host cell's, and therefore the child would be be the
offspring of two different females.]
=====================================================
--------------------------------------------------------------------------
"FOR as long as he can remember Stuart Kauffman has held a deep
conviction about nature: that natural selection cannot be the sole or even
the most important source of order in the biological world. Almost three
decades ago, Kauffman, then a young medical student at the University of
California, San Francisco, set out to prove he was right and that the rest of
the biological community was wrong. `What I found was profound,' says
Kauffman. `I knew that then and I'm still convinced of it.' ... The
mechanism of controls by feedback that Jacob and Monod found in these
systems struck a chord in Kauffman's still unformulated thinking about
order in biological systems, and led to the computer simulation
experiments. `The results were so powerful, and seemed to confirm what I
felt instinctively must be true, that I dismissed natural selection as being
totally unimportant,' says Kauffman." (Lewin R., "Order For Free," New
Scientist, 13 February 1993, Supplement, pp.10,11)
Stephen E. Jones | sejones@iinet.net.au | http://www.iinet.net.au/~sejones
--------------------------------------------------------------------------
This archive was generated by hypermail 2b29 : Thu May 18 2000 - 19:29:29 EDT