Re: In Lice, Clues to Human Origin and Attire


"Day Brown" <daybrown@xxxxxxxxxx> wrote in message
news:1173661726.894966.310600@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
One quibble. "Demonic Males" by Wrangham & Peterson report that one of
the diffs with the Bonobo is that there is *no* sign of estrus. No
odor, no flush. They also mention "Hoka-hoka", in which the females
engage in lesbian sex. And that unlike the other apes, in which the
males are 200-300% larger, with the Bonobo the males are only 20-30%
larger.

There is only one other primate with all these characteristics.
hominids.

But I wonder about the dating. I've read of "punctuated" evolution.
And we know that higher levels of radiation increase the mutation
rate. It'd be interesting to see if any of the nearby stars went Nova
and thereby drenched the earth with radiation, and doing so much more
on the side of the earth facing the radioactive source.


love them bonobos! I think a lot of info about ourselves can be discovered
from them... if we can manage to study them before they go extinct.
--chap

re: the puncuated equilibrium:
http://pespmc1.vub.ac.be/PUNCTUEQ.html
http://en.wikipedia.org/wiki/Punctuated_equilibrium

re: the supernova question (people are looking....):
http://www.sciencenews.org/articles/20060107/fob7.asp
Gauging Star Birth: Spacecraft uses gamma rays as stellar tracer
Ron Cowen
By detecting the radioactive remains of material hurled into space by dying
stars, astronomers have estimated that, on average, our galaxy churns out
seven new stars each year.





The researchers used the European Space Agency's INTEGRAL spacecraft to
record gamma-ray light, which is high-energy radiation undetectable from
Earth's surface. They collected the particular wavelength that arises from
the radioactive decay of aluminum-26. The distribution of this aluminum
isotope traces the location of dead massive stars in the Milky Way. These
stellar heavyweights forge nearly all the galaxy's aluminum, which they
expel when they die in explosions known as supernovas.

The INTEGRAL team, led by Roland Diehl of the Max Planck Institute for
Extraterrestrial Physics in Garching, Germany, confirmed that aluminum-26 is
found primarily in star-forming regions of the galaxy. In the Jan. 5 Nature,
the researchers conclude that over the past few million years, an average of
two massive stars per century have died as supernovas in the galaxy.

Using theoretical models of the number of massive stars in relation to the
total number of stars in the Milky Way, the team also calculated that seven
new stars appear each year and that their total mass is about four times
that of the sun.

That star-formation rate agrees with those derived from other methods of
estimating star birth, notes study coauthor Dieter Hartmann of Clemson
University in South Carolina.

Determining star-formation rates in the Milky Way galaxy is a tricky
business, he adds. Astronomers have previously used visible and ultraviolet
light emitted by newborn stars. However, such radiation is obscured by gas
and dust clouds that tend to concentrate in the Milky Way's spiral arms,
where most new stars form. In contrast, gamma rays easily penetrate these
clouds.

Aluminum-26's relatively long half-life of 750,000 years also aided in the
new estimate, says Hartmann. That longevity enabled INTEGRAL to record the
emissions from stars that perished during the past several million years.

Diehl and other researchers had previously constructed maps of the galaxy's
aluminum-26 by using less-sensitive instruments, such as a detector on the
now-defunct Compton Gamma Ray Observatory (SN: 1/25/92, p. 53). But in those
older maps, researchers were concerned that a significant amount of the
gamma-ray emission might be coming from the sun's neighborhood or star
formation at a few localized sources rather than from throughout the galaxy.

The spectrometer on INTEGRAL, launched in 2002, has a critical advantage
over previous detectors. It's sensitive enough to record a variety of tiny
shifts in the wavelength of gamma-ray light that arise from the rotation of
objects spread across the Milky Way.

The shift "is telling us that the aluminum-26 is almost certainly associated
with the [entire] galaxy," rather than just a few locations within it,
according to James Kurfess of the Naval Research Laboratory in Washington,
D.C. The new map therefore validates the use of aluminum-26 as a highly
precise gauge of the recent history of supernovas and star birth in the
Milky Way, he adds.

http://www.sciencenews.org/articles/20040221/note17.asp
Finding the star that was
Ron Cowen

Sifting through archival images, astronomers have identified the star whose
explosive demise was recorded by telescopes last year. It's the third time
scientists have observed what a particular star looked like before it was
blown to smithereens and the first time that they've uncovered the origin of
the most common type of supernova. The discovery confirms the accepted
theory that type II supernovas are produced when elderly, bloated stars
known as red supergiants run out of nuclear fuel and collapse.




A team led by Stephen Smartt of the University of Cambridge in England
describes the find in the Jan. 23 Science.

The researchers began their search for archived images of the star last
June, after an amateur astronomer, using a backyard telescope, found a
supernova in the galaxy M74, about 30 million light-years from Earth. As
luck would have it, both the Hubble Space Telescope and the Gemini North
Telescope on Hawaii's Mauna Kea had imaged the original star less than a
year before the supernova find. The images reveal that the red supergiant
star was about 8 times as massive as the sun, which is near the low end of
what theory predicts for the mass of stars that can flame out in a
supernova.

Previous archive searches for images of stars that ended their lives as
supernovas have rarely met with success. That's because no star has gone
supernova in our own galaxy for several hundred years, and more-distant
stars in other galaxies weren't clearly imaged until recent years.


.

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