Here also is a site for Anthropology in the News from Texas A & M.
Homo erectus, in this new framework, is a species that gradually evolved from about 2 Ma from a crafty little scavenger into the large, advanced, hunting predator that made the wonderful Acheulean tool kit, including hand axes. Erectus spread out of Africa into Eurasia, and its fossils are found from Spain and France to northern China and Indonesia.
In Africa and Europe, erectus evolved into Homo heidelbergensis, which in turn evolved in Europe and western Asia into Homo neanderthalensis. In Siberia, erectus evolved into the Denisovans, and in Indonesia, a small isolated offshoot of erectus is seen at the "hobbits" of Flores, Homo floresiensis.
African heidelbergensis evolved into Homo sapiens, which then took over the world. But there was enough inbreeding with previous Homo in Africa, Europe, and Asia that non-sapiens genes were transmitted to sapiens at low percentages. (Intensive research continues on this aspect.)
This story is simpler and cleaner than the older multiplication of early Homo species, and allows us to concentrate on the story of erectus as a major breakthrough in hominid evolution. (See the news update on the shoulder of erectus below.)
The paper is in Science this week, so is not freely available on the Web.
Just a little while ago, this impact idea seemed dead. But two new papers present strong evidence that there was some sort of impact. Petaev et al. show that there is a large platinum spike in dust particles in the Greenland ice cap, right at 12,800 BP, the time when the anomalous cold climate of the Younger Dryas begins. The platinum was deposited in perhaps 20 years, in keeping with the lifetime of very fine dust in the stratosphere. The impactor may have been an iridium-poor iron meteorite, the authors say.
Then Wittke et al. report analyses of 700 spherules from 18 sites at the Younger Dryas boundary. They infer a relatively large asteroid impact, though their calculations are based on relatively few sites compared with the KT data.
So we have new studies that are not necessarily compatible with one another. Clearly there is more going on than we had thought, and one or more impacts seem to have occurred. Having established that, we can go on to worry about the nature and mass of the impactor(s), and then what their effect on climate and humans and ecosystems might have been.
Petaev, M. I. et al. 2013. Large Pt anomaly in the Greenland ice core points to a cataclysm at the onset of Younger Dryas. PNAS 110: 12917-12920
Wittke, J. H. et al. 2013. Evidence for deposition of 10 million tonnes of impact spherules across four continents 12,800 y ago. PNAS 110: E2088-2097.
The new paper is in Nature, so it is not on the Web. Abe-Ouchi, A. et al. 2013. Insolation-driven 100,000-year glacial cycles and hysteresis of ice-sheet volume. Nature 500, 190–193; and comment, pp. 159-160. So see this news story from a strange Japanese site comment from Science, and watch this video of one computer run: Video showing the computer model of ice ages
And, of course, there's a teaching moment here. The similarity of the PT and the KT mass extinctions means a lot in terms of a general theory. There will be more encouragement for looking for a convincing end-Triassic impact (there are already papers about candidates). The hydrocarbon factor becomes important too. Is Earth more likely to suffer mass extinctions through time as organic productivity has increased? Probably yes, but carbon has to be buried where it is geologically vulnerable to disturbances such as impacts. It's a bit scary that a fairly small impact like Araguainha could be part of the largest ever mass extinction, but it happened at the best (worst) time and place.
If you write a textbook, something will eventually happen which makes you wish you could rewrite a chapter. This is one of those times, and it's only months since it became too late to change Chapter 6 of History of Life!
This is a careful study and it is likely to be a landmark paper. Tohver, E. et al. 2013. Shaking a methane fizz: Seismicity from the Araguainha impact event and the Permian–Triassic global carbon isotope record. Palaeogeography, Palaeoclimatology, Palaeoecology 387, 66–75. Here is a news story from The Economist by Matt Kaplan: The Economist
We have footprints of an Australopithecus from East Africa about 3.3 Ma (A. afarensis or Lucy) that walked freely in an upright stance, and we have Homo erectus as an early Homo that had a skeleton for walking upright and footprints to match. It make no sense at all (to me) that striding bipedal (open-country) australopithecines should evolve into a hyperpronating arboreal specialist sediba, but would then reverse that evolution, lose all its specialized anatomy, and re-evolve into a striding open-country biped (Homo erectus and all later Homo).
Yet that is what Lee Berger would like to see, as he continues to describe sediba as a "at the very least, a possible ancestor" of Homo. Now there's a long tradition of African-based paleoanthropologists stubbornly resisting criticism until they were proved right: Raymond Dart with Australopithecus africanus, and Louis Leakey with Homo habilis. But William of Ockham is spinning in his grave at this point, because Berger's view of sediba is far from the simplest hypothesis for A. sediba. We wait and see....
November 18, 2012. A new Cambrian Burgess Shale basal arthropod Nereocaris helps to suggest that arthropod skeletonization was linked with stabilizing the muscular system that allowed swimming. Therefore arthropods were originally swimmers and all their adaptations to benthic life on and in the substrate came later (say the authors). The paper is in the Proceedings of the Royal Society B
July 18, 2011. More evidence that humans interbred to a limited extent with Neanderthals, but only outside Africa since Neanderthals evolved outside Africa. The paper is in Molecular Biology and Evolution.
VACATION GAP, SLOWLY BEING FILLED
July 6, 2011. Photosynthesis confirmed in stromatolites at 3.3 Ga. No surprise, just honest analysis. Not published yet. Nature news site
If the trackway story's correct
It shows something we didn't expect:
There they are, hand in hand,
Making tracks in the sand
And the male's walking fully erect.
ADDENDA. Dr. Rosie Redfield has written a blog that contains lethal objections to the paper. If the objections are valid, then the evidence presented by the authors does not support their extravagant claims. The blog is being revised and polished continuously to take into account relevant comments. Wait and see.... Rrresearch blog by Rosie Redfield, version as of December 4, 2010
And here is a different but equally devastating critique: Guest blog by Dr. Alex Bradley, December 5, 2010.
And here is an informal poll of major scientists on the paper, taken by Carl Zimmer for Slate magazine: Slate magazine, December 7, 2010.
And here is an overview of an eventful week: Ed Yong's blog in Discover, December 11, 2010.
For stories archived from 2010, see Paleontology News 2010
For stories archived from 2009, see Paleontology News 2009
For stories archived from 2008, see Paleontology News 2008
For stories archived from 2007, see Paleontology News 2007
For stories archived from 2006, see Paleontology News 2006
For stories archived from 2005, see Paleontology News 2005
For stories archived from 2004, see Paleontology News 2004
For stories archived from 2003, see Paleontology News 2003
For stories archived from 2002, see Paleontology News 2002
For stories archived from 2001, see Paleontology News 2001
For stories archived from 2000, see Paleontology News 2000
For stories archived from 1999, see Paleontology News 1999
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