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I've been saving this picture for more than a year, not showing it to anyone or posting it anywhere online, not wanting to break the embargo:

This was a picture I took of one of the fossils brought to SciFoo'07 by Paul Sereno and Gabrielle Lyon, together with the skull of Nigersaurus.

Apparently, while digging for dinosaurs in Niger, Paul and the crew discovered an enormous and fascinating archaeological site - Gobero. They teamed up with anthropologists and archaeologists and spent two digging seasons analysing the site. The first results of this study are now finally published in my favourite journal - PLoS ONE:

Lakeside Cemeteries in the Sahara: 5000 Years of Holocene Population and Environmental Change

Background

Approximately two hundred human burials were discovered on the edge of a paleolake in Niger that provide a uniquely preserved record of human occupation in the Sahara during the Holocene (~8000 B.C.E. to the present). Called Gobero, this suite of closely spaced sites chronicles the rapid pace of biosocial change in the southern Sahara in response to severe climatic fluctuation.

Methodology/Principal Findings

Two main occupational phases are identified that correspond with humid intervals in the early and mid-Holocene, based on 78 direct AMS radiocarbon dates on human remains, fauna and artifacts, as well as 9 OSL dates on paleodune sand. The older occupants have craniofacial dimensions that demonstrate similarities with mid-Holocene occupants of the southern Sahara and Late Pleistocene to early Holocene inhabitants of the Maghreb. Their hyperflexed burials compose the earliest cemetery in the Sahara dating to ~7500 B.C.E. These early occupants abandon the area under arid conditions and, when humid conditions return ~4600 B.C.E., are replaced by a more gracile people with elaborated grave goods including animal bone and ivory ornaments.

Conclusions/Significance

The principal significance of Gobero lies in its extraordinary human, faunal, and archaeological record, from which we conclude the following:

1. The early Holocene occupants at Gobero (7700-6200 B.C.E.) were largely sedentary hunter-fisher-gatherers with lakeside funerary sites that include the earliest recorded cemetery in the Sahara.

2. Principal components analysis of craniometric variables closely allies the early Holocene occupants at Gobero with a skeletally robust, trans-Saharan assemblage of Late Pleistocene to mid-Holocene human populations from the Maghreb and southern Sahara.

3. Gobero was abandoned during a period of severe aridification possibly as long as one millennium (6200-5200 B.C.E).

4. More gracile humans arrived in the mid-Holocene (5200-2500 B.C.E.) employing a diversified subsistence economy based on clams, fish, and savanna vertebrates as well as some cattle husbandry.

5. Population replacement after a harsh arid hiatus is the most likely explanation for the occupational sequence at Gobero.

6. We are just beginning to understand the anatomical and cultural diversity that existed within the Sahara during the Holocene.

You can see more pictures and the background story on the Project Exploration site.

Greg Laden has already posted about it, and I hope other bloggers will as well.

I am not an expert on human evolution, but if I understand correctly, the information gathered at the site shows that Sahara was going through cycles: being very dry for some time, then having lakes and forests for some time, then getting dry again, etc. During dry periods, no humans lived there. During wet periods, this place was inhabited by humans - but not the same kinds of humans!

The earlier group, if I understand this right, were large, strong humans who subsisted on large game hunting and harpooning huge Nile perch. They are direct descendants of early human ancestors, i.e., they have evolved in Africa, and only their later descendants went out of Africa to Middle East, Europe and beyond.

The latter group came to the site about a 1000 years later. They were smaller and more gracile, made tools, ornamented their pots in very different ways, they kept animals, did some fishing, perhaps some agriculture. They buried their dead on beds of flowers. They may have, but I am not sure about this, be descendants of Eurasian humans, i.e., they may have come back from the Middle East or Europe into Africa and settled there.

The National Geographic story about the finding is a riveting read - I strongly suggest you read it whole. And I hope you read the paper itself (it is NOT a tough slog through highly technical lingo) and see all the additional information about human remains, artefacts, animal and plant remains, and new methods of analysis. And I hope you post comments, ratings and notes on the paper and, if you blog about it, send trackbacks.

Reference:

Lakeside Cemeteries in the Sahara: 5000 Years of Holocene Population and Environmental Change by Paul C. Sereno, Elena A. A. Garcea, Helene Jousse, Christopher M. Stojanowski, Jean-Francois Salieege, Abdoulaye Maga, Oumarou A. Ide, Kelly J. Knudson, Anna Maria Mercuri, Thomas W. Stafford, Jr., Thomas G. Kaye1 , Carlo Giraudi, Isabella Massamba N'siala, Enzo Cocca, Hannah M. Moots, Didier B. Dutheil and Jeffrey P. Stivers. PLoS ONE 3(8): e2995. doi:10.1371/journal.pone.0002995

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Update - more coverage:

Anthropology.net: The Kiffian & Tenerean Occupation Of Gobero, Niger: Perhaps The Largest Collection Of Early-Mid Holocene People In Africa
Greg Laden: Stone Age Graveyard Reveals Lifestyles of a Green Sahara
Pharyngula: I wish I was a Paleontologist
Sociolingo's Africa: African archaeology Niger : Saharan cemetery dig report and paper
Ontogeny: Burial site offers rare glimpse of daily life in the stone-age Sahara
Pro-science: Stone Age graveyeard found in Sahara
Knight Science Journalism Tracker: AP, Chicago Trib, New Scientist, NYTimes, etc: Dino hunters find, instead, an ancient human graveyard in the Sahara
L.A.Times: Archaeologists get a glimpse of life in a Sahara Eden