Thanks to GP for the link.

Reposted from:
http://www.sciencedaily.com/releases/2008/12/081219172137.htm

ScienceDaily (Dec. 21, 2008) — A research team led by Professor Michael Chazan, director of the University of Toronto's Archaeology Centre, has discovered the earliest evidence of our cave-dwelling human ancestors at the Wonderwerk Cave in South Africa.

Stone tools found at the bottom level of the cave — believed to be 2 million years old — show that human ancestors were in the cave earlier than ever thought before. Geological evidence indicates that these tools were left in the cave and not washed into the site from the outside world.

Archaeological investigations of the Wonderwerk cave — a South African National Heritage site due to its role in discovering the human and environmental history of the area — began in the 1940s and research continues to this day.

Using a combination of dating methods it has been possible to date the bottom level reached by Peter Beaumont in the front part of the cave to 2 million years ago.
A small number of very small stone tools have been recovered from excavations in this level. Geological evidence indicates that these tools were deposited in the cave by human ancestors, not washed into the site from the outside.

The combination of stone tools indicating the presence of human ancestors and the dating of the level leads to the conclusion that human ancestors (hominids) were in the cave 2 million years ago. This is the earliest evidence for intentional cave occupation by human ancestors.

There were a number of species of hominids in southern Africat 2 million years ago. The most likely candidate as the manufacturer of the stone tools found at Wonderwerk is Homo habilis.

The oldest known stone tools from sites in Ethiopia date to 2.4 million years. The Wonderwerk Cave discoveries are those close in age to the very earliest known stone tools and similar in date to the bottom levels at Olduvai Gorge.

How the site was dated

The deposits at Wonderwerk Cave built up over time so that the deeper one excavates the layers become older. The trick is to figure out exactly how old the levels are. We used two methods that together provide a secure date.

For Paleomagnetic Dating Hagai Ron of the Hebrew University took small samples of soil from the entire sequence (over fifty samples). These samples allow him to measure changes in he earth’s magnetic field and to correlate the Wonderwerk sequence with a global timescale for changes in the magnetic field (known as reversals).

For Cosmogenic Burial Age Ari Matmon, also from the Hebrew University, took soil samples and carefully prepared them in the lab. He then sent these samples to an atomic accelerator in the United States where a procedure to measure isotopes, much like the method used in carbon dating, was carried out. Unlike carbon dating, Cosmogenic Burial Age dating can provide very old dates.

Why was this so difficult? Most well dated early sites are in East Africa where there are volcanic ash layers that can be dated using the Argon method. In southern Africa we lack these ash layers so that we need to develop new methods. The first use of Cosmogenic Burial Age dating in South Africa was at the Cradle of Humankind. Our results show the value of this method, particularly when combined with Paledating, for archaeological research both in the region and globally.

About Wonderwerk Cave

The Wonderwerk Cave is located in Northern Cape Province, South Africa between Danielskuil and Kuruman. The cave formed by water action in the Dolemite rocks of the Asbestos Hills. This rock formation is over 2 billion years old, some of the oldest rock on earth, so we do not know when exactly the cave formed.

The cave runs 130 meters from front to back. Wonderwerk discovered was discovered when local farmers dug up large parts of the cave in the 1940’s to sell the sediments for fertilizer. Subsequently a series of brief archaeological excavations began. Peter Beaumont of the McGregor Museum carried out major excavations at the site between 1978-1993.