serendipity (06-10-2023)
serendipity (06-10-2023)
It's still an open question whether Homo sapiens are descendants of Homo erectus, but I thought the author gave a good summary of possible transitional species.
The Daka skull, which is about 1 million years old and hails from the
Awash, was found in Ethiopia in the late 1990s and consists of only
the calvaria. It has a reconstructed cranial capacity of about 995 cubic
centimeters—well within the range expected of Homo erectus. However,
based on its shape and other measurements, this transitional fossil has been
used to argue for a direct evolutionary relationship between Homo erectus
and Homo sapiens. Fast-forwarding another 500,000 years in the same
region, the discovery of a much later example—the Gawis cranium—has
been presented as yet another transitional form, demonstrating the link
between Homo erectus and Homo sapiens.
Paleoanthropologists have named multiple other species that could serve
as transitional types.
For example, the Ndutu cranium—discovered on the
shores of Lake Ndutu at Olduvai in Tanzania—dates to between 400,000 and
600,000 years old. Like Homo erectus, it has a sloping forehead and a thick
skull. However, it lacks the sagittal torus and is slightly bulbous, more like the
skull of Homo sapiens. As a result, this specimen has been proposed to belong
to yet another taxon: Homo rhodesiensis. This species was named in 1921,
when Zambia was called Northern Rhodesia.Homo rhodesiensis is also used to describe the famous fossil of Kabwe 1,
or Broken Hill. The remains consist of a complete cranium, a sacrum, a
tibia, and two femoral fragments. Today, it’s thought to be about 300,000
years old. Rather than looking like something between Homo erectus and Homo sapiens, this sample has some Neanderthal-like characteristics as well, begging the question as to whether Homo rhodesiensis might be ancestral
to the Neanderthals rather than to our own species.
Another relative, the Bodo cranium—discovered in the Awash of Ethiopia and dating to 600,000
years before present—might be a more likely candidate for an erectus-sapiens
link. However, it’s also considered a member of the Homo rhodesiensis group.
This species is potentially synonymous with a European form called Homo
heidelbergensis, after a specimen discovered in Germany.
The oldest currently accepted specimens of Homo sapiens, Omo 1 and Omo
2, were discovered in 1967. They are close to 195,000 years old. What makes
them so distinctive is their rounded, dome-like skulls; thin brow ridges;
chins; and, most importantly, an even larger brain than before, at 1,400 cubic
centimeters. The other earliest Homo sapiens specimens, sometimes referred to as Homo sapiens idaltu, or “first born,” discovered in the late 1990s from Herto in the Middle Awash, share similar anatomical features and large
braincases. They’ve been argued to be directly ancestral to us.
Source credit, Suzanne Pilaar Birch, Univ of Georgia
guno (06-02-2023)
serendipity (06-10-2023)
guno (06-02-2023)
The US Geological Survey doesn't seem to think Yellowstone is primed for any new eruptions in the immediate future (https://www.usgs.gov/faqs/yellowston...lowstone-erupt)
Just from a time perspective (and volcanoes don't really go on schedule) it may be another 100,000 years before the next one. And they think only 5-15% of the magma chamber is molten.
It's apparently rhyolitic (felsic, silica rich) so it should be reasonably explosive, but apparently not an imminent danger at this time. Even so there was a less explosive eruption about back about 70ka.
But, who really knows?
A Yellowstone super eruption is a complete hypothetical of something that might not happen for hundreds of thousands of years. It's nearly pointless as a topic of discussion on major environmental problems..
Global warming is a reality and anthropogenic signatures are all over the GHG accumulating in the atmosphere
Excellence is an art won by training and habituation. We do not act rightly because we have virtue or excellence, but rather we have those because we have acted rightly. We are what we repeatedly do. Excellence, then, is not an act but a habit.
- -- Aristotle
Believe nothing on the faith of traditions, even though they have been held in honor for many generations and in diverse places. Do not believe a thing because many people speak of it. Do not believe on the faith of the sages of the past. Do not believe what you yourself have imagined, persuading yourself that a God inspires you. Believe nothing on the sole authority of your masters and priests. After examination, believe what you yourself have tested and found to be reasonable, and conform your conduct thereto.
- -- The Buddha
It is the mark of an educated mind to be able to entertain a thought without accepting it.
- -- Aristotle
Interestingly enough we know a lot about climate forcings (including CO2) from eruptions like Mt. Pinatubo. The amount of CO2 coming out of volcanoes is usually less than the amount that humans pump into the atmosphere every year but when they do it provides helpful information on the "climate sensitivity" of things like CO2 which lets us know that CO2 is, indeed, a very important greenhouse gas that we are responsible for.
No one thinks CO2 is the only factor (in fact if you read the IPCC you'll see a whole host of them) but CO2 is a large one related to our actions. We can even find a "fingerprint" pointing directly to human activity in the increased CO2 in the atmosphere. It's the carbon isotopes that show us we are responsible for a huge chunk of the increased CO2 in the atmosphere.
But, again, no one thinks it is ONLY CO2.
Patriotism is the last refuge of a scoundrel. Samuel Johnson, 1775
Religion....is the opiate of the people. Karl Marx, 1848
Freedom's just another word for nothin' left to lose. Kris Kristofferson, 1969
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