Friday, September 6, 2013

SA: The Fossil Caves

After all the conference shenanigans were over, it was time for some sight-seeing. I had asked round to see if anyone wanted to come with me--I was hoping a local would volunteer and drive--but the forensic anthropologist who offered backed out at the last minute. However, he set me up with a very nice post-doc out at Sterkfontein Caves, part of the World Heritage Site Cradle of Humankind, the world's richest deposit of hominid remains.

The next morning I rented a car and GPS unit and set out. This was not without the hassle of having to go back to the hotel to get my original passport out of the safe box, since they wouldn't accept an uncertified copy; however, by that time they had located a car with an automatic transmission for me. I thought having to figure out how to drive on the left would be a challenge enough without also having to remember how to drive a stick shift! Driving on the "wrong" side of the road turned out to be easier than I had anticipated, because the streets are set up for two-way traffic: you just have to put your car where someone else's isn't. (It's harder to be a pedestrian.) It probably helped that there were lots of signs warning that cameras were checking our speed, so I closely monitored my lead-foot tendencies.

It was a beautiful if very warm day. I got a personal tour of the dig site, both the outside pits and the indoor areas, where highly trained workers painstakingly remove fossils from the rock in which they are embedded. While we were there, one of the diggers pointed out a tooth he had uncovered, probably from a jackal or hyena. Someone else's *entire* job is to break up the stones the miners left.

Dem bones
The area was once a great inland lake whose bottom filled with dolomite. Slightly acidic water seeped into the dolomite and created underwater caves. As the water level dropped, these filled with air--and then debris. It was mostly dirt, vegetation, and bones broken by predators eating in the trees above, but sometimes a whole body would fall down the vertical shafts that opened in weak spots. Calcium carbonate was laid down very slowly, fossilizing everything. Over time, the ceilings collapsed, and earthquakes raised other parts, so deeper does not necessarily mean older. Miners in the 1890s looking for limestone to aid in purification of gold ore discovered the first fossils. Systematic excavation began in 1936, halted temporarily during WWII, and continues to this day.

The rocks range from 4.2 million years old to 200,000 years old. The fossils are up to 3 million years old; there are also stone tools 2 million years old. This is where the hominid genus Australopithecus was first discovered (yes, before "Lucy"!). The two most famous finds are "Mrs. Ples," a 2.1-million-year-old Australopithecus skull found in 1947, and "Little Foot," an almost complete child skeleton that is 2-3 million years old and was painstakingly uncovered in 1994-1998. A paleoanthropologist noticed some of his foot bones first, then he sent workers in with flashlights to search the caves for the matching bit of stone where it broke off. Amazingly, they found it in just two days! If I had had a light, we could have seen that part of the caves (Silberberg Grotto), which is not open to the public.

For lunch, the post doc recommended "not the salad" from the little eatery in the visitors' center, so I ordered a cheap but tasty grilled ham, cheese, and tomato sandwich. Then it was time for the guided tour. The post doc let me into the mini-museum for free: sweet. I was soon joined by a class of hospitality students and a few elderly Italian tourists. The exhibits chronicle the geological history of the Sterkfontein caves, how prospecting for minerals led to the discovery of the first fossils, and the evolution of Homo sapiens. The displays are quite nicely done, as you can see.

Then it was time to enter the caves. The outside path had all kinds of interesting factoids scattered along it. For instance, "Mrs. Ples" is actually a male skull, which is why the name always appears in quotation marks. Our guide showed us how to work a clever sundial. Finally, we tramped down the stairs into the cool dark.

There were stalactites and stalagmites, oh my! Walking wasn't too difficult, as most of the path is on rubber grids. There is also a large underground lake. Once three divers tried to figure out how deep it is, but one became lost when his rope snagged and cut on a rock. He scrawled a message for his mother and his new wife on the rock before he died when his oxygen tank ran out. No one has been allowed to dive in the lake since then. Our tour ended with the ascent, part of which required some creativity to fit through a narrow passage: crab-walk, duck-walk, or bear-walk for the older gentleman whose knees didn't bend so well.

Either the continent of Africa or an elephant. Which do you see?
A statuette of paleontologist Dr. Robert Broom (1866-1951) holding a replica of "Mrs Ples" guards the exit to the caves. You can either rub his nose for luck or his left hand for wisdom. (Which do you think I chose?) Although I had the rental car for several more hours, I decided I had had enough adventure for one day. I skipped the main fossil museum at Maropeng as well as a nearby lion preserve to return to my hotel and finish an abstract that was due for another conference at midnight.
Wish me luck!

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